Patent Publication Number: US-2023144436-A1

Title: Muscle targeting complexes and uses thereof for treating myotonic dystrophy

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of the filing date of U.S. Provisional Application No. 63/132,856, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF”, filed Dec. 31, 2020; U.S. Provisional Application No. 63/069,063, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”, filed Aug. 23, 2020; U.S. Provisional Application No. 63/055,499, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”, filed Jul. 23, 2020; U.S. Provisional Application No. 62/968,383, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”, filed Jan. 31, 2020; U.S. Provisional Application No. 62/965,712, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”, filed Jan. 24, 2020; and U.S. Provisional Application No. 62/959,776, entitled “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”, filed Jan. 10, 2020; the contents of each of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present application relates to targeting complexes for delivering molecular payloads (e.g., oligonucleotides) to cells and uses thereof, particularly uses relating to treatment of disease. 
     REFERENCE TO SEQUENCE LISTING SUBMITTED AS A TEXT FILE VIA EFS-WEB 
     The instant application contains a sequence listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jan. 8, 2021, is named D082470029W000-SEQ-ZJG and is 762 kilobytes in size. 
     BACKGROUND 
     Myotonic dystrophy (DM) is a dominantly inherited genetic disease that is characterized by myotonia, muscle loss or degeneration, diminished muscle function, insulin resistance, cardiac arrhythmia, smooth muscle dysfunction, and neurological abnormalities. DM is the most common form of adult-onset muscular dystrophy, with a worldwide incidence of about 1 in 8000 people worldwide. Two types of the disease, myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2), have been described. DM1, the more common form of the disease, results from a repeat expansion of a CTG trinucleotide repeat in the 3′ non-coding region of DMPK on chromosome 19; DM2 results from a repeat expansion of a CCTG tetranucleotide repeat in the first intron of ZNF9 on chromosome 3. In DM1 patients, the repeat expansion of a CTG trinucleotide repeat, which may comprise greater than ˜50 to ˜3,000+ total repeats, leads to generation of toxic RNA repeats capable of forming hairpin structures that bind essential intracellular proteins, e.g. muscleblind-like proteins, with high affinity resulting in protein sequestration and the loss-of-function phenotypes that are characteristic of the disease. Apart from supportive care and treatments to address the symptoms of the disease, no effective therapeutic for DM1 is currently available. 
     SUMMARY 
     In some aspects, the disclosure provides complexes that target muscle cells for purposes of delivering molecular payloads to those cells. In some embodiments, complexes provided herein are particularly useful for delivering molecular payloads that inhibit the expression or activity of a DMPK allele comprising an expanded disease-associated-repeat, e.g., in a subject having or suspected of having myotonic dystrophy. Accordingly, in some embodiments, complexes provided herein comprise muscle-targeting agents (e.g., muscle targeting antibodies) that specifically bind to receptors on the surface of muscle cells for purposes of delivering molecular payloads to the muscle cells. In some embodiments, the complexes are taken up into the cells via a receptor mediated internalization, following which the molecular payload may be released to perform a function inside the cells. For example, complexes engineered to deliver oligonucleotides may release the oligonucleotides such that the oligonucleotides can inhibit mutant DMPK expression in the muscle cells. In some embodiments, the oligonucleotides are released by endosomal cleavage of covalent linkers connecting oligonucleotides and muscle-targeting agents of the complexes. 
     Some aspects of the present disclosure provide complexes comprising an anti-transferrin receptor antibody covalently linked to a molecular payload configured for inhibiting DMPK expression or activity. In some embodiments, the anti-TfR antibody comprises a heavy chain complementarity determining region 1 (CDR-H1), a heavy chain complementarity determining region 2 (CDR-H2), a heavy chain complementarity determining region 3 (CDR-H3), a light chain complementarity determining region 1 (CDR-L1), a light chain complementarity determining region 2 (CDR-L2), a light chain complementarity determining region 3 (CDR-L3) of any of the anti-TfR antibodies listed in Table 2, 4, and 7. 
     In some embodiments, the antibody comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable region (VH) comprising the amino acid sequence of SEQ ID NO: 15, and a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable region (VL) comprising the amino acid sequence of SEQ ID NO: 16. In some embodiments, the antibody comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 204, and a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 205. In some embodiments, the antibody comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 7, and a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 8. In some embodiments, the antibody comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 23, and a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 24. 
     In some embodiments, the antibody comprises a CDR-H1 of SEQ ID NO: 155, a CDR-H2 of SEQ ID NO: 156, a CDR-H3 of SEQ ID NO: 157, a CDR-L1 of SEQ ID NO: 158, a CDR-L2 of SEQ ID NO: 159, and a CDR-L3 of SEQ ID NO: 14. In some embodiments, the antibody comprises a CDR-H1 of SEQ ID NO: 194, a CDR-H2 of SEQ ID NO: 195, a CDR-H3 of SEQ ID NO: 196, a CDR-L1 of SEQ ID NO: 197, a CDR-L2 of SEQ ID NO: 198, and a CDR-L3 of SEQ ID NO: 193. In some embodiments, the antibody comprises a CDR-H1 of SEQ ID NO: 145, a CDR-H2 of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734, a CDR-H3 of SEQ ID NO: 147, a CDR-L1 of SEQ ID NO: 148, a CDR-L2 of SEQ ID NO: 149, and a CDR-L3 of SEQ ID NO: 6. In some embodiments, the antibody comprises: a CDR-H1 of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738, a CDR-H2 of SEQ ID NO: 166, a CDR-H3 of SEQ ID NO: 167, a CDR-L1 of SEQ ID NO: 168, a CDR-L2 of SEQ ID NO: 169, and a CDR-L3 of SEQ ID NO: 22. 
     In some embodiments, the antibody comprises human or humanized framework regions with the CDR-H1, the CDR-H2, the CDR-H3 of a VH as set forth in SEQ ID NO: 15, and the CDR-L1, the CDR-L2, the CDR-L3 of a VL as set forth in SEQ ID NO: 16. In some embodiments, the antibody comprises human or humanized framework regions with the CDR-H1, the CDR-H2, the CDR-H3 of a VH as set forth in SEQ ID NO: 204, and the CDR-L1, the CDR-L2, the CDR-L3 of a VL as set forth in SEQ ID NO: 205. In some embodiments, the antibody comprises human or humanized framework regions with the CDR-H1, the CDR-H2, the CDR-H3 of a VH as set forth in SEQ ID NO: 7, and the CDR-L1, the CDR-L2, the CDR-L3 of a VL as set forth in SEQ ID NO: 8. In some embodiments, the antibody comprises human or humanized framework regions with the CDR-H1, the CDR-H2, the CDR-H3 of a VH as set forth in SEQ ID NO: 23, and the CDR-L1, the CDR-L2, the CDR-L3 of a VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the antibody comprises a VH comprising an amino acid sequence at least 80% identical to SEQ ID NO: 15, and a VL comprising an amino acid sequence at least 80% identical to SEQ ID NO: 16. In some embodiments, the antibody comprises a VH comprising an amino acid sequence at least 80% identical to SEQ ID NO: 204, and a VL comprising an amino acid sequence at least 80% identical to SEQ ID NO: 205, optionally wherein the antibody comprises a VH comprising the amino acid sequence of SEQ ID NO: 204 and a VL comprising the amino acid sequence of SEQ ID NO: 205. In some embodiments, the antibody comprises a VH comprising an amino acid sequence at least 80% identical to SEQ ID NO: 7, and a VL comprising an amino acid sequence at least 80% identical to SEQ ID NO: 8. In some embodiments, the antibody comprises a VH comprising an amino acid sequence at least 80% identical to SEQ ID NO: 23, and a VL comprising an amino acid sequence at least 80% identical to SEQ ID NO: 24. 
     In some embodiments, the equilibrium dissociation constant (K D ) of binding of the antibody to the transferrin receptor is in a range from 10 −11 M to 10 −6  M. 
     In some embodiments, the antibody is selected from the group consisting of a full-length IgG, a Fab fragment, a F(ab′) fragment, a F(ab′)2 fragment, a scFv, and a Fv, optionally wherein the antibody is a Fab′ fragment. 
     In some embodiments, the molecular payload is an oligonucleotide. 
     In some embodiments, the oligonucleotide comprises a region of complementarity to at least 15 consecutive nucleotides of SEQ ID NO: 727. 
     In some embodiments, the oligonucleotide comprises a region of complementarity to at least 15 consecutive nucleotides of any one of SEQ ID NO: 482-717. 
     In some embodiments, the oligonucleotide comprises at least 15 consecutive nucleotides of a sequence comprising any one of SEQ ID NOs: 246-481 and 778-795, optionally wherein the oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 246-481 and 778-795. 
     In some embodiments, the oligonucleotide comprises at least one modified internucleoside linkage. In some embodiments, the at least one modified internucleoside linkage is a phosphorothioate linkage. 
     In some embodiments, the oligonucleotide comprises one or more modified nucleosides, optionally wherein the one or more modified nucleosides are 2′-modified nucleosides. 
     In some embodiments, the oligonucleotide is a gapmer oligonucleotide that directs RNAse H-mediated cleavage of a DMPK mRNA transcript. 
     In some embodiments, the gapmer oligonucleotide comprises a 5′-X-Y-Z-3′ formula. In some embodiments, 
     X comprises 3-5 linked nucleosides, wherein at least one of the nucleosides in X is a 2′-modified nucleoside; 
     Y comprises 6-10 linked 2′-deoxyribonuclsides, wherein one or more of the nucleosides in the gap region Y is a modified nucleoside, and wherein one or more cytosines in the gap region Y are optionally 5-methyl-cytosines; and 
     Z comprises 3-5 linked nucleosides, wherein at least one of the nucleosides in Z is a 2′-modified nucleoside. 
     In some embodiments, each nucleoside in X and Z is a 2′modified nucleoside. 
     In some embodiments, the 2′ modified nucleotide is selected from the group consisting of: 2′-O-methyl (2′-O-Me), 2′-fluoro (2′-F), 2′-O-methoxyethyl (2′-MOE), and 2′, 4′-bicyclic nucleosides, further optionally wherein the 2′,4′-bicyclic nucleoside is selected from: locked nucleic acid (LNA), ethylene-bridged nucleic acid (ENA), and (S)-constrained ethyl-bridged nucleic acid (cEt). 
     In some embodiments, the muscle-targeting agent is covalently linked to the molecular payload via a cleavable linker. In some embodiments, the cleavable linker comprises a valine-citrulline dipeptide sequence. In some embodiments, the muscle-targeting agent is covalently linked to the molecular payload via a non-cleavable linker. In some embodiments, the non-cleavable linker is an alkane linker. 
     In some embodiments, the molecular payload is linked to the antibody via conjugation to a lysine residue or a cysteine residue of the antibody. 
     Other aspects of the present disclosure provide methods of inhibiting activity of DMPK in a cell. In some embodiments, the method comprises contacting the cell with the complex described herein in an amount effective for promoting internalization of the molecular payload to the cell. In some embodiments, the cell comprises a DMPK allele comprising a disease-associated-repeat. 
     Other aspects of the present disclosure provide methods of treating a subject having an expansion of a disease-associated-repeat of a DMPK allele that is associated with myotonic dystrophy type 1 (DM1). In some embodiments, the methods comprise administering to the subject an effective amount of the complex described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a non-limiting schematic showing the effect of transfecting Hepa 1-6 cells with an antisense oligonucleotide that targets DMPK (control DMPK-ASO) on expression levels of DMPK relative to a vehicle transfection. 
         FIG.  2 A  depicts a non-limiting schematic showing an HIL-HPLC trace obtained during purification of a muscle targeting complex comprising an anti-transferrin receptor antibody covalently linked to a DMPK antisense oligonucleotide. 
         FIG.  2 B  depicts a non-limiting image of an SDS-PAGE analysis of a muscle targeting complex. 
         FIG.  3    depicts a non-limiting schematic showing the ability of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO to reduce expression levels of DMPK. 
         FIGS.  4 A- 4 E  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO to reduce expression levels of DMPK in mouse muscle tissues in vivo, relative to a vehicle experiment. (N=3 C57Bl/6 WT mice) 
         FIGS.  5 A- 5 B  depict non-limiting schematics showing the tissue selectivity of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO. The muscle targeting complex (DTX-C-008) comprising control DMPK-ASO does not reduce expression levels of DMPK in mouse brain or spleen tissues in vivo, relative to a vehicle experiment. (N=3 C57Bl/6 WT mice) 
         FIGS.  6 A- 6 F  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO to reduce expression levels of DMPK in mouse muscle tissues in vivo, relative to a vehicle experiment. (N=5 C57Bl/6 WT mice) 
         FIGS.  7 A- 7 L  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-012) comprising an anti-transferrin receptor antibody (a 15G11 antibody) and control DMPK-ASO to reduce expression levels of DMPK in cynomolgus monkey muscle tissues in vivo, relative to a vehicle experiment and compared to a naked DMPK ASO (control DMPK-ASO). (N=3 male cynomolgus monkeys) 
         FIGS.  8 A- 8 B  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-012) comprising an anti-transferrin receptor antibody (a 15G11 antibody) and control DMPK-ASO to reduce expression levels of DMPK in cynomolgus monkey smooth muscle tissues in vivo, relative to a vehicle experiment and compared to a naked DMPK ASO (control DMPK-ASO). (N=3 male cynomolgus monkeys). 
         FIGS.  9 A- 9 D  depict non-limiting schematics showing the tissue selectivity of a muscle targeting complex (DTX-C-012) comprising an anti-transferrin receptor antibody (a 15G11 antibody) and control DMPK-ASO. The muscle targeting complex comprising DMPK-ASO does not reduce expression levels of DMPK in cynomolgus monkey liver, kidney, brain, or spleen tissues in vivo, relative to a vehicle experiment. (N=3 male cynomolgus monkeys) 
         FIG.  10    shows normalized DMPK mRNA tissue expression levels across several tissue types in cynomolgus monkeys. (N=3 male cynomolgus monkeys) 
         FIGS.  11 A- 11 B  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO to reduce expression levels of DMPK in mouse muscle tissues in vivo for up to 28 days after dosing with DTX-C-008, relative to a vehicle experiment and compared to a naked DMPK ASO (control DMPK-ASO). 
         FIG.  12    shows that a single dose of a muscle targeting complex (DTX-C-012) comprising an anti-transferrin receptor antibody (a 15G11 antibody) and control DMPK-ASO is safe and tolerated in cynomolgus monkeys. (N=3 male cynomolgus monkeys) 
         FIGS.  13 A- 13 B  depict non-limiting schematics showing the ability of a muscle targeting complex (DTX-C-008) comprising control DMPK-ASO to reduce expression levels of DMPK in mouse muscle tissues in vivo for up to twelve weeks after dosing with DTX-C-008, relative to a vehicle treatment; and compared to a control complex (DTX-C-007) and naked DMPK ASO (control DMPK-ASO). (N=5 C57Bl/6 WT mice) 
         FIGS.  14 A- 14 B  depict non-limiting schematics showing the ability of a muscle-targeting complex (DTX-C-008) comprising control DMPK-ASO to target nuclear mutant DMPK RNA in a mouse model. (N=6 mice) 
         FIGS.  15 A- 15 B  depict non-limiting schematics showing the ability of a muscle-targeting complex (DTX-Actin) comprising an oligonucleotide that targets actin to dose-dependently reduce expression levels of actin and functional grades of myotonia in muscle tissues. (N=2 HSA LR  mice) 
         FIGS.  16 A- 16 C  depict non-limiting schematics showing that a muscle-targeting complex (DTX-C-008) is capable of significantly reducing the prolonged QTc interval in a mouse model for validation of the functional correction of arrhythmia in a DM1 cardiac model. (N=10 mice)  FIG.  16 A  shows a schematic of the human DMPK construct driving the mouse model of DM1,  FIG.  16 B  shows measured QRS intervals, and  FIG.  16 C  shows measured QTc intervals. 
         FIGS.  17 A- 17 B  depict non-limiting schematics showing that a muscle-targeting complex (DTX-C-012) comprising an anti-transferrin receptor antibody (a 15G11 antibody) and control DMPK-ASO antisense oligonucleotide is capable of reducing expression levels of DMPK and correcting splicing of a DMPK-specific target gene (Bin1) in human cells from a DM1 patient. (N=3) 
         FIGS.  18 A- 18 C  depict non-limiting schematics showing the dose response of selected antisense oligonucleotides in DMPK knockdown in human DM1 myotubes. ControlDMPK-ASO was used as control. All tested oligonucleotides showed activity in DMPK knockdown. Statistical analysis: One-way ANOVA with Tukey&#39;s HSD post-hoc test vs. control DMPK-ASO treatment; *p&lt;0.05, **p&lt;0.01, ***p&lt;0.001, ****p&lt;0.0001. 
         FIGS.  19 A- 19 B  depict non-limiting schematics showing the dose response of selected antisense oligonucleotides in DMPK knockdown in non-human primate (NHP) DM1 myotubes. Control DMPK-ASO was used as control. All tested oligonucleotides showed activity in DMPK knockdown. 
         FIG.  20    is a graph showing DMPK knock down efficiency in non-human primate (NHP) cells or cells from human DM1 patients (DM1) of conjugates containing selected anti-TfR1 antibodies covalently conjugated to an antisense oligonucleotide targeting DMPK. 
         FIGS.  21 A to  21 B  show binding of the different anti-TfR1 antibody formats to human ( FIG.  21 A ) or cyno ( FIG.  21 B ) transferrin receptor 1. 
         FIG.  22    shows binding of the different anti-TfR1 antibody formats to human transferrin receptor 2. An anti-TfR2 monoclonal antibody (OTI1B1) was used as control. None of the tested antibodies binds to TfR2. 
         FIG.  23    is a graph showing DMPK knock down efficiency in non-human primate (NHP) cells or cells from human DM1 patients (DM1) of conjugates containing an anti-TfR1 antibody described herein covalently conjugated to an antisense oligonucleotide targeting DMPK. 
         FIGS.  24 A- 24 B  show binding of oligonucleotide-conjugated or unconjugated anti-TfR to human TfR1 (hTfR1) and cynomolgus monkey TfR1 (cTfR1), as measured by ELISA. The anti-TfR is the one shown in Table 7.  FIG.  24 A  shows the binding of the anti-TfR alone (EC50 26.6 nM) or in conjugates with a DMPK targeting oligo (EC50 8.2 nM) to hTfR1.  FIG.  24 B  shows the binding of the anti-TfR alone (EC50 33.6 nM) or in conjugates with a DMPK targeting oligo (EC50 5.3 nM) to cTfR1. 
         FIG.  25    shows the quantified cellular uptake of anti-TfR Fab conjugates into rhabdomyosarcoma (RD) cells. The molecular payload in the tested conjugates are DMPK-targeting oligonucleotides and the uptake of the conjugates were facilitated by indicated anti-TfR Fabs. Conjugates having a negative control Fab (anti-mouse TfR) or a positive control Fab (anti-human TfR1) are also included this assay. Cells were incubated with indicated conjugate at a concentration of 100 nM for 4 hours. Cellular uptake was measured by mean Cypher5e fluorescence. The anti-TfR is the one shown in Table 7. 
         FIG.  26    shows DMPK expression in RD cells treated with various concentrations of conjugates containing an anti-TfR antibody (the anti-TfR in Table 7) conjugated to a DMPK-targeting oligonucleotide (control DMPK-ASO). The duration treatment was 3 days. Control DMPK-ASO delivered using transfection agents were used as control. 
         FIG.  27    shows the serum stability of the linker used for linking an anti-TfR antibody and a molecular payload (e.g., an oligonucleotide) in various species over time after intravenous administration. 
         FIG.  28    shows DMPK expression in RD cells treated with DMPK-targeting oligonucleotides relative to cells treated with PBS. The duration of treatment was 3 days. DMPK-targeting oligonucleotides were delivered to the cells as free oligonucleotides (gymnotic uptake, “free”) or with transfection reagent (“trans”). 
         FIG.  29    shows results of splicing correction in Atp2a1 by an anti-TfR1 antibody-oligonucleotide conjugate (Ab-ASO) in the HSA-LR mouse model of DM1, measured in the gastrocnemius muscle. The anti-TfR used is RI7 217 and the oligonucleotide is targeting skeletal actin. 
         FIGS.  30 A- 30 C  show splicing correction in more than 30 different RNAs related to DM1, measured in the gastrocnemius muscle of HSA-LR mice treated with anti-TfR1 antibody-oligonucleotide (Ab-ASO) conjugate or saline. The anti-TfR used is RI7 217 and the oligonucleotide is targeting skeletal actin. 
         FIG.  31    shows splicing derangement in quadriceps, gastrocnemius, or tibialis anterior muscles of HSA-LR mice treated with anti-TfR1 antibody-oligonucleotide conjugate (Ab-ASO) or saline. The data represent composite splicing derangement measured in the more than 30 RNAs shown in  FIGS.  30 A- 30 C . 
         FIG.  32    shows myotonia grade measured in quadriceps, gastrocnemius, and tibialis anterior muscles of HSA-LR mice treated with saline, unconjugated oligonucleotide (ASO), or anti-TfR1 antibody-oligonucleotide conjugate (Ab-ASO). Myotonia was measured by electromyography (EMG), and graded 0, 1, 2, or 3 based on the frequency of myotonic discharge. 
         FIGS.  33 A- 33 D  show in vivo activity of conjugates containing an anti-TfR Fab′ (a control anti-TfR Fab′ or an anti-TfR Fab′ comprising a HC of SEQ ID NO: 777 and a LC of SEQ ID NO: 212) conjugated to DMPK-targeting oligonucleotide in reducing DMPK mRNA expression in mice expressing human TfR1 (hTfR1 knock-in mice). Remaining DMPK mRNA levels were measured 14 days post first dose in the tibialis anterior ( FIG.  33 A ), gastrocnemius ( FIG.  33 B ), heart ( FIG.  33 C ), and diaphragm ( FIG.  33 D ), of the mice. In  FIGS.  33 A- 33 D , p&lt;0.05 (*); p&lt;0.01 (**); p&lt;0.001 (***); p&lt;0.0001 (****). 
         FIGS.  34 A- 34 C  show that conjugates containing anti-TfR conjugated to DMPK-targeting oligonucleotide corrected splicing and reduced foci in CM-DM1-32F primary cells expressing a DMPK mutant mRNA containing 380 GTG repeats.  FIG.  34 A  shows that the conjugates reduced mutant DMPK mRNA expression.  FIG.  34 B  shows that the conjugates corrected BIN1 Exon 11 splicing.  FIG.  34 C  shows images of a fluorescence in situ hybridization (FISH) analysis and quantification of the images, demonstrating that the conjugated reduced nuclear foci formed by the mutant DMPK mRNA. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the disclosure relate to a recognition that while certain molecular payloads (e.g., oligonucleotides, peptides, small molecules) can have beneficial effects in muscle cells, it has proven challenging to effectively target such cells. As described herein, the present disclosure provides complexes comprising muscle-targeting agents covalently linked to molecular payloads in order to overcome such challenges. In some embodiments, the complexes are particularly useful for delivering molecular payloads that inhibit the expression or activity of target genes in muscle cells, e.g., in a subject having or suspected of having a rare muscle disease. For example, in some embodiments, complexes are provided for targeting a DMPK allele that comprises an expanded disease-associated-repeat to treat subjects having DM1. In some embodiments, complexes provided herein may comprise oligonucleotides that inhibit expression of a DMPK allele comprising an expanded disease-associated-repeat. As another example, complexes may comprise oligonucleotides that interfere with the binding of a disease-associated DMPK mRNA to a muscleblind-like protein (e.g., MBNL1, 2, and/or (e.g., and) 3), thereby reducing a toxic effect of a disease-associated DMPK allele. In some embodiments, synthetic nucleic acid payloads (e.g., DNA or RNA payloads) may be used that express one or more proteins that reduce a toxic effect of a disease-associated DMPK allele. In some embodiments, complexes may comprise molecular payloads of synthetic cDNAs and/or (e.g., and) synthetic mRNAs, e.g., that express one or more muscleblind-like-proteins (e.g., MBNL1, 2, and/or (e.g., and) 3) or fragments thereof. In some embodiments, complexes may comprise molecular payloads such as guide molecules (e.g., guide RNAs) that are capable of targeting nucleic acid programmable nucleases (e.g., Cas9) to a sequence at or near a disease-associated repeat sequence of DMPK. In some embodiments, such nucleic programmable nucleases could be used to cleave part or all of a disease-associated repeat sequence from a DMPK gene. 
     Further aspects of the disclosure, including a description of defined terms, are provided below. 
     I. Definitions 
     Administering: As used herein, the terms “administering” or “administration” means to provide a complex to a subject in a manner that is physiologically and/or (e.g., and) pharmacologically useful (e.g., to treat a condition in the subject). 
     Approximately: As used herein, the term “approximately” or “about,” as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain embodiments, the term “approximately” or “about” refers to a range of values that fall within 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value). 
     Antibody: As used herein, the term “antibody” refers to a polypeptide that includes at least one immunoglobulin variable domain or at least one antigenic determinant, e.g., paratope that specifically binds to an antigen. In some embodiments, an antibody is a full-length antibody. In some embodiments, an antibody is a chimeric antibody. In some embodiments, an antibody is a humanized antibody. However, in some embodiments, an antibody is a Fab fragment, a F(ab′), a F(ab′)2 fragment, a Fv fragment or a scFv fragment. In some embodiments, an antibody is a nanobody derived from a camelid antibody or a nanobody derived from shark antibody. In some embodiments, an antibody is a diabody. In some embodiments, an antibody comprises a framework having a human germline sequence. In another embodiment, an antibody comprises a heavy chain constant domain selected from the group consisting of IgG, IgG1, IgG2, IgG2A, IgG2B, IgG2C, IgG3, IgG4, IgA1, IgA2, IgD, IgM, and IgE constant domains. In some embodiments, an antibody comprises a heavy (H) chain variable region (abbreviated herein as VH), and/or (e.g., and) a light (L) chain variable region (abbreviated herein as VL). In some embodiments, an antibody comprises a constant domain, e.g., an Fc region. An immunoglobulin constant domain refers to a heavy or light chain constant domain. Human IgG heavy chain and light chain constant domain amino acid sequences and their functional variations are known. With respect to the heavy chain, in some embodiments, the heavy chain of an antibody described herein can be an alpha (α), delta (Δ), epsilon (ε), gamma (γ) or mu (μ) heavy chain. In some embodiments, the heavy chain of an antibody described herein can comprise a human alpha (α), delta (Δ), epsilon (ε), gamma (γ) or mu (μ) heavy chain. In a particular embodiment, an antibody described herein comprises a human gamma 1 CH1, CH2, and/or (e.g., and) CH3 domain. In some embodiments, the amino acid sequence of the VH domain comprises the amino acid sequence of a human gamma (γ) heavy chain constant region, such as any known in the art. Non-limiting examples of human constant region sequences have been described in the art, e.g., see U.S. Pat. No. 5,693,780 and Kabat E A et al., (1991) supra. In some embodiments, the VH domain comprises an amino acid sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, or at least 99% identical to any of the variable chain constant regions provided herein. In some embodiments, an antibody is modified, e.g., modified via glycosylation, phosphorylation, sumoylation, and/or (e.g., and) methylation. In some embodiments, an antibody is a glycosylated antibody, which is conjugated to one or more sugar or carbohydrate molecules. In some embodiments, the one or more sugar or carbohydrate molecule are conjugated to the antibody via N-glycosylation, O-glycosylation, C-glycosylation, glypiation (GPI anchor attachment), and/or (e.g., and) phosphoglycosylation. In some embodiments, the one or more sugar or carbohydrate molecule are monosaccharides, disaccharides, oligosaccharides, or glycans. In some embodiments, the one or more sugar or carbohydrate molecule is a branched oligosaccharide or a branched glycan. In some embodiments, the one or more sugar or carbohydrate molecule includes a mannose unit, a glucose unit, an N-acetylglucosamine unit, an N-acetylgalactosamine unit, a galactose unit, a fucose unit, or a phospholipid unit. In some embodiments, an antibody is a construct that comprises a polypeptide comprising one or more antigen binding fragments of the disclosure linked to a linker polypeptide or an immunoglobulin constant domain. Linker polypeptides comprise two or more amino acid residues joined by peptide bonds and are used to link one or more antigen binding portions. Examples of linker polypeptides have been reported (see e.g., Holliger, P., et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak, R. J., et al. (1994) Structure 2:1121-1123). Still further, an antibody may be part of a larger immunoadhesion molecule, formed by covalent or noncovalent association of the antibody or antibody portion with one or more other proteins or peptides. Examples of such immunoadhesion molecules include use of the streptavidin core region to make a tetrameric scFv molecule (Kipriyanov, S. M., et al. (1995) Human Antibodies and Hybridomas 6:93-101) and use of a cysteine residue, a marker peptide and a C-terminal polyhistidine tag to make bivalent and biotinylated scFv molecules (Kipriyanov, S. M., et al. (1994) Mol. Immunol. 31:1047-1058). 
     CDR: As used herein, the term “CDR” refers to the complementarity determining region within antibody variable sequences. There are three CDRs in each of the variable regions of the heavy chain and the light chain, which are designated CDR1, CDR2 and CDR3, for each of the variable regions. The term “CDR set” as used herein refers to a group of three CDRs that occur in a single variable region capable of binding the antigen. The exact boundaries of these CDRs have been defined differently according to different systems. The system described by Kabat (Kabat et al., Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md. (1987) and (1991)) not only provides an unambiguous residue numbering system applicable to any variable region of an antibody, but also provides precise residue boundaries defining the three CDRs. These CDRs may be referred to as Kabat CDRs. Sub-portions of CDRs may be designated as L1, L2 and L3 or H1, H2 and H3 where the “L” and the “H” designates the light chain and the heavy chains regions, respectively. These regions may be referred to as Chothia CDRs, which have boundaries that overlap with Kabat CDRs. Other boundaries defining CDRs overlapping with the Kabat CDRs have been described by Padlan (FASEB J. 9:133-139 (1995)) and MacCallum (J Mol Biol 262(5):732-45 (1996)). Still other CDR boundary definitions may not strictly follow one of the above systems, but will nonetheless overlap with the Kabat CDRs, although they may be shortened or lengthened in light of prediction or experimental findings that particular residues or groups of residues or even entire CDRs do not significantly impact antigen binding. The methods used herein may utilize CDRs defined according to any of these systems, although preferred embodiments use Kabat or Chothia defined CDRs. 
     CDR-grafted antibody: The term “CDR-grafted antibody” refers to antibodies which comprise heavy and light chain variable region sequences from one species but in which the sequences of one or more of the CDR regions of VH and/or (e.g., and) VL are replaced with CDR sequences of another species, such as antibodies having murine heavy and light chain variable regions in which one or more of the murine CDRs (e.g., CDR3) has been replaced with human CDR sequences. 
     Chimeric antibody: The term “chimeric antibody” refers to antibodies which comprise heavy and light chain variable region sequences from one species and constant region sequences from another species, such as antibodies having murine heavy and light chain variable regions linked to human constant regions. 
     Complementary: As used herein, the term “complementary” refers to the capacity for precise pairing between two nucleotides or two sets of nucleotides. In particular, complementary is a term that characterizes an extent of hydrogen bond pairing that brings about binding between two nucleotides or two sets of nucleotides. For example, if a base at one position of an oligonucleotide is capable of hydrogen bonding with a base at the corresponding position of a target nucleic acid (e.g., an mRNA), then the bases are considered to be complementary to each other at that position. Base pairings may include both canonical Watson-Crick base pairing and non-Watson-Crick base pairing (e.g., Wobble base pairing and Hoogsteen base pairing). For example, in some embodiments, for complementary base pairings, adenosine-type bases (A) are complementary to thymidine-type bases (T) or uracil-type bases (U), that cytosine-type bases (C) are complementary to guanosine-type bases (G), and that universal bases such as 3-nitropyrrole or 5-nitroindole can hybridize to and are considered complementary to any A, C, U, or T. Inosine (I) has also been considered in the art to be a universal base and is considered complementary to any A, C, U or T. 
     Conservative amino acid substitution: As used herein, a “conservative amino acid substitution” refers to an amino acid substitution that does not alter the relative charge or size characteristics of the protein in which the amino acid substitution is made. Variants can be prepared according to methods for altering polypeptide sequence known to one of ordinary skill in the art such as are found in references which compile such methods, e.g. Molecular Cloning: A Laboratory Manual, J. Sambrook, et al., eds., Fourth Edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 2012, or Current Protocols in Molecular Biology, F. M. Ausubel, et al., eds., John Wiley &amp; Sons, Inc., New York. Conservative substitutions of amino acids include substitutions made amongst amino acids within the following groups: (a) M, I, L, V; (b) F, Y, W; (c) K, R, H; (d) A, G; (e) S, T; (f) Q, N; and (g) E, D. 
     Covalently linked: As used herein, the term “covalently linked” refers to a characteristic of two or more molecules being linked together via at least one covalent bond. In some embodiments, two molecules can be covalently linked together by a single bond, e.g., a disulfide bond or disulfide bridge, that serves as a linker between the molecules. However, in some embodiments, two or more molecules can be covalently linked together via a molecule that serves as a linker that joins the two or more molecules together through multiple covalent bonds. In some embodiments, a linker may be a cleavable linker. However, in some embodiments, a linker may be a non-cleavable linker. 
     Cross-reactive: As used herein and in the context of a targeting agent (e.g., antibody), the term “cross-reactive,” refers to a property of the agent being capable of specifically binding to more than one antigen of a similar type or class (e.g., antigens of multiple homologs, paralogs, or orthologs) with similar affinity or avidity. For example, in some embodiments, an antibody that is cross-reactive against human and non-human primate antigens of a similar type or class (e.g., a human transferrin receptor and non-human primate transferrin receptor) is capable of binding to the human antigen and non-human primate antigens with a similar affinity or avidity. In some embodiments, an antibody is cross-reactive against a human antigen and a rodent antigen of a similar type or class. In some embodiments, an antibody is cross-reactive against a rodent antigen and a non-human primate antigen of a similar type or class. In some embodiments, an antibody is cross-reactive against a human antigen, a non-human primate antigen, and a rodent antigen of a similar type or class. 
     Disease-associated-repeat: As used herein, the term “disease-associated-repeat” refers to a repeated nucleotide sequence at a genomic location for which the number of units of the repeated nucleotide sequence is correlated with and/or (e.g., and) directly or indirectly contributes to, or causes, genetic disease. Each repeating unit of a disease associated repeat may be 2, 3, 4, 5 or more nucleotides in length. For example, in some embodiments, a disease associated repeat is a dinucleotide repeat. In some embodiments, a disease associated repeat is a trinucleotide repeat. In some embodiments, a disease associated repeat is a tetranucleotide repeat. In some embodiments, a disease associated repeat is a pentanucleotide repeat. In some embodiments, embodiments, the disease-associated-repeat comprises CAG repeats, CTG repeats, CUG repeats, CGG repeats, CCTG repeats, or a nucleotide complement of any thereof. In some embodiments, a disease-associated-repeat is in a non-coding portion of a gene. However, in some embodiments, a disease-associated-repeat is in a coding region of a gene. In some embodiments, a disease-associated-repeat is expanded from a normal state to a length that directly or indirectly contributes to, or causes, genetic disease. In some embodiments, a disease-associated-repeat is in RNA (e.g., an RNA transcript). In some embodiments, a disease-associated-repeat is in DNA (e.g., a chromosome, a plasmid). In some embodiments, a disease-associated-repeat is expanded in a chromosome of a germline cell. In some embodiments, a disease-associated-repeat is expanded in a chromosome of a somatic cell. In some embodiments, a disease-associated-repeat is expanded to a number of repeating units that is associated with congenital onset of disease. In some embodiments, a disease-associated-repeat is expanded to a number of repeating units that is associated with childhood onset of disease. In some embodiments, a disease-associated-repeat is expanded to a number of repeating units that is associated with adult onset of disease. 
     DMPK: As used herein, the term “DMPK” refers to a gene that encodes myotonin-protein kinase (also known as myotonic dystrophy protein kinase or dystrophia myotonica protein kinase), a serine/threonine protein kinase. Substrates for this enzyme may include myogenin, the beta-subunit of the L-type calcium channels, and phospholemman. In some embodiments, DMPK may be a human (Gene ID: 1760), non-human primate (e.g., Gene ID: 456139, Gene ID: 715328), or rodent gene (e.g., Gene ID: 13400). In humans, a CTG repeat expansion in the 3′ non-coding, untranslated region of DMPK is associated with myotonic dystrophy type I (DM1). In addition, multiple human transcript variants (e.g., as annotated under GenBank RefSeq Accession Numbers: NM_001081563.2, NM_004409.4, NM_001081560.2, NM_001081562.2, NM_001288764.1, NM_001288765.1, and NM_001288766.1) have been characterized that encode different protein isoforms. 
     DMPK allele: As used herein, the term “DMPK allele” refers to any one of alternative forms (e.g., wild-type or mutant forms) of a DMPK gene. In some embodiments, a DMPK allele may encode for wild-type myotonin-protein kinase that retains its normal and typical functions. In some embodiments, a DMPK allele may comprise one or more disease-associated-repeat expansions. In some embodiments, normal subjects have two DMPK alleles comprising in the range of 5 to 37 repeat units. In some embodiments, the number of CTG repeat units in subjects having DM1 is in the range of ˜50 to ˜3,000+ with higher numbers of repeats leading to an increased severity of disease. In some embodiments, mildly affected DM1 subjects have at least one DMPK allele having in the range of 50 to 150 repeat units. In some embodiments, subjects with classic DM1 have at least one DMPK allele having in the range of 100 to 1,000 or more repeat units. In some embodiments, subjects having DM1 with congenital onset may have at least one DMPK allele comprising more than 2,000 repeat units. 
     Framework: As used herein, the term “framework” or “framework sequence” refers to the remaining sequences of a variable region minus the CDRs. Because the exact definition of a CDR sequence can be determined by different systems, the meaning of a framework sequence is subject to correspondingly different interpretations. The six CDRs (CDR-L1, CDR-L2, and CDR-L3 of light chain and CDR-H1, CDR-H2, and CDR-H3 of heavy chain) also divide the framework regions on the light chain and the heavy chain into four sub-regions (FR1, FR2, FR3 and FR4) on each chain, in which CDR1 is positioned between FR1 and FR2, CDR2 between FR2 and FR3, and CDR3 between FR3 and FR4. Without specifying the particular sub-regions as FR1, FR2, FR3 or FR4, a framework region, as referred by others, represents the combined FRs within the variable region of a single, naturally occurring immunoglobulin chain. As used herein, a FR represents one of the four sub-regions, and FRs represents two or more of the four sub-regions constituting a framework region. Human heavy chain and light chain acceptor sequences are known in the art. In one embodiment, the acceptor sequences known in the art may be used in the antibodies disclosed herein. 
     Human antibody: The term “human antibody”, as used herein, is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human antibodies of the disclosure may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs and in particular CDR3. However, the term “human antibody”, as used herein, is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences. 
     Humanized antibody: The term “humanized antibody” refers to antibodies which comprise heavy and light chain variable region sequences from a non-human species (e.g., a mouse) but in which at least a portion of the VH and/or (e.g., and) VL sequence has been altered to be more “human-like”, i.e., more similar to human germline variable sequences. One type of humanized antibody is a CDR-grafted antibody, in which human CDR sequences are introduced into non-human VH and VL sequences to replace the corresponding nonhuman CDR sequences. In one embodiment, humanized anti-transferrin receptor antibodies and antigen binding portions are provided. Such antibodies may be generated by obtaining murine anti-transferrin receptor monoclonal antibodies using traditional hybridoma technology followed by humanization using in vitro genetic engineering, such as those disclosed in Kasaian et al PCT publication No. WO 2005/123126 A2. 
     Internalizing cell surface receptor: As used herein, the term, “internalizing cell surface receptor” refers to a cell surface receptor that is internalized by cells, e.g., upon external stimulation, e.g., ligand binding to the receptor. In some embodiments, an internalizing cell surface receptor is internalized by endocytosis. In some embodiments, an internalizing cell surface receptor is internalized by clathrin-mediated endocytosis. However, in some embodiments, an internalizing cell surface receptor is internalized by a clathrin-independent pathway, such as, for example, phagocytosis, macropinocytosis, caveolae- and raft-mediated uptake or constitutive clathrin-independent endocytosis. In some embodiments, the internalizing cell surface receptor comprises an intracellular domain, a transmembrane domain, and/or (e.g., and) an extracellular domain, which may optionally further comprise a ligand-binding domain. In some embodiments, a cell surface receptor becomes internalized by a cell after ligand binding. In some embodiments, a ligand may be a muscle-targeting agent or a muscle-targeting antibody. In some embodiments, an internalizing cell surface receptor is a transferrin receptor. 
     Isolated antibody: An “isolated antibody”, as used herein, is intended to refer to an antibody that is substantially free of other antibodies having different antigenic specificities (e.g., an isolated antibody that specifically binds transferrin receptor is substantially free of antibodies that specifically bind antigens other than transferrin receptor). An isolated antibody that specifically binds transferrin receptor complex may, however, have cross-reactivity to other antigens, such as transferrin receptor molecules from other species. Moreover, an isolated antibody may be substantially free of other cellular material and/or (e.g., and) chemicals. 
     Kabat numbering: The terms “Kabat numbering”, “Kabat definitions and “Kabat labeling” are used interchangeably herein. These terms, which are recognized in the art, refer to a system of numbering amino acid residues which are more variable (i.e. hypervariable) than other amino acid residues in the heavy and light chain variable regions of an antibody, or an antigen binding portion thereof (Kabat et al. (1971) Ann. NY Acad, Sci. 190:382-391 and, Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242). For the heavy chain variable region, the hypervariable region ranges from amino acid positions 31 to 35 for CDR1, amino acid positions 50 to 65 for CDR2, and amino acid positions 95 to 102 for CDR3. For the light chain variable region, the hypervariable region ranges from amino acid positions 24 to 34 for CDR1, amino acid positions 50 to 56 for CDR2, and amino acid positions 89 to 97 for CDR3. 
     Molecular payload: As used herein, the term “molecular payload” refers to a molecule or species that functions to modulate a biological outcome. In some embodiments, a molecular payload is linked to, or otherwise associated with a muscle-targeting agent. In some embodiments, the molecular payload is a small molecule, a protein, a peptide, a nucleic acid, or an oligonucleotide. In some embodiments, the molecular payload functions to modulate the transcription of a DNA sequence, to modulate the expression of a protein, or to modulate the activity of a protein. In some embodiments, the molecular payload is an oligonucleotide that comprises a strand having a region of complementarity to a target gene. 
     Muscle-targeting agent: As used herein, the term, “muscle-targeting agent,” refers to a molecule that specifically binds to an antigen expressed on muscle cells. The antigen in or on muscle cells may be a membrane protein, for example an integral membrane protein or a peripheral membrane protein. Typically, a muscle-targeting agent specifically binds to an antigen on muscle cells that facilitates internalization of the muscle-targeting agent (and any associated molecular payload) into the muscle cells. In some embodiments, a muscle-targeting agent specifically binds to an internalizing, cell surface receptor on muscles and is capable of being internalized into muscle cells through receptor mediated internalization. In some embodiments, the muscle-targeting agent is a small molecule, a protein, a peptide, a nucleic acid (e.g., an aptamer), or an antibody. In some embodiments, the muscle-targeting agent is linked to a molecular payload. 
     Muscle-targeting antibody: As used herein, the term, “muscle-targeting antibody,” refers to a muscle-targeting agent that is an antibody that specifically binds to an antigen found in or on muscle cells. In some embodiments, a muscle-targeting antibody specifically binds to an antigen on muscle cells that facilitates internalization of the muscle-targeting antibody (and any associated molecular payment) into the muscle cells. In some embodiments, the muscle-targeting antibody specifically binds to an internalizing, cell surface receptor present on muscle cells. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds to a transferrin receptor. 
     Myotonic dystrophy (DM): As used herein, the term “Myotonic dystrophy (DM)” refers to a genetic disease caused by mutations in the DMPK gene or CNBP (ZNF9) gene that is characterized by muscle loss, muscle weakening, and muscle function. Two types of the disease, myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2), have been described. DM1 is associated with an expansion of a CTG trinucleotide repeat in the 3′ non-coding region of DMPK. DM2 is associated with an expansion of a CCTG tetranucleotide repeat in the first intron of ZNF9. In both DM1 and DM2, the nucleotide expansions lead to toxic RNA repeats capable of forming hairpin structures that bind critical intracellular proteins, e.g., muscleblind-like proteins, with high affinity. Myotonic dystrophy, the genetic basis for the disease, and related symptoms are described in the art (see, e.g. Thornton, C. A., “Myotonic Dystrophy” Neurol Clin. (2014), 32(3): 705-719.; and Konieczny et al. “Myotonic dystrophy: candidate small molecule therapeutics” Drug Discovery Today (2017), 22:11.) In some embodiments, subjects are born with a variation of DM1 called congenital myotonic dystrophy. Symptoms of congenital myotonic dystrophy are present from birth and include weakness of all muscles, breathing problems, clubfeet, developmental delays and intellectual disabilities. DM1 is associated with Online Mendelian Inheritance in Man (OMIM) Entry #160900. DM2 is associated with OMIM Entry #602668. 
     Oligonucleotide: As used herein, the term “oligonucleotide” refers to an oligomeric nucleic acid compound of up to 200 nucleotides in length. Examples of oligonucleotides include, but are not limited to, RNAi oligonucleotides (e.g., siRNAs, shRNAs), microRNAs, gapmers, mixmers, phosphorodiamidite morpholinos, peptide nucleic acids, aptamers, guide nucleic acids (e.g., Cas9 guide RNAs), etc. Oligonucleotides may be single-stranded or double-stranded. In some embodiments, an oligonucleotide may comprise one or more modified nucleotides (e.g. 2′-O-methyl sugar modifications, purine or pyrimidine modifications). In some embodiments, an oligonucleotide may comprise one or more modified internucleotide linkage. In some embodiments, an oligonucleotide may comprise one or more phosphorothioate linkages, which may be in the Rp or Sp stereochemical conformation. 
     Recombinant antibody: The term “recombinant human antibody”, as used herein, is intended to include all human antibodies that are prepared, expressed, created or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector transfected into a host cell (described in more details in this disclosure), antibodies isolated from a recombinant, combinatorial human antibody library (Hoogenboom H. R., (1997) TIB Tech. 15:62-70; Azzazy H., and Highsmith W. E., (2002) Clin. Biochem. 35:425-445; Gavilondo J. V., and Larrick J. W. (2002) BioTechniques 29:128-145; Hoogenboom H., and Chames P. (2000) Immunology Today 21:371-378), antibodies isolated from an animal (e.g., a mouse) that is transgenic for human immunoglobulin genes (see e.g., Taylor, L. D., et al. (1992) Nucl. Acids Res. 20:6287-6295; Kellermann S-A., and Green L. L. (2002) Current Opinion in Biotechnology 13:593-597; Little M. et al (2000) Immunology Today 21:364-370) or antibodies prepared, expressed, created or isolated by any other means that involves splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences. In certain embodiments, however, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when an animal transgenic for human Ig sequences is used, in vivo somatic mutagenesis) and thus the amino acid sequences of the VH and VL regions of the recombinant antibodies are sequences that, while derived from and related to human germline VH and VL sequences, may not naturally exist within the human antibody germline repertoire in vivo. One embodiment of the disclosure provides fully human antibodies capable of binding human transferrin receptor which can be generated using techniques well known in the art, such as, but not limited to, using human Ig phage libraries such as those disclosed in Jermutus et al., PCT publication No. WO 2005/007699 A2. 
     Region of complementarity: As used herein, the term “region of complementarity” refers to a nucleotide sequence, e.g., of a oligonucleotide, that is sufficiently complementary to a cognate nucleotide sequence, e.g., of a target nucleic acid, such that the two nucleotide sequences are capable of annealing to one another under physiological conditions (e.g., in a cell). In some embodiments, a region of complementarity is fully complementary to a cognate nucleotide sequence of target nucleic acid. However, in some embodiments, a region of complementarity is partially complementary to a cognate nucleotide sequence of target nucleic acid (e.g., at least 80%, 90%, 95% or 99% complementarity). In some embodiments, a region of complementarity contains 1, 2, 3, or 4 mismatches compared with a cognate nucleotide sequence of a target nucleic acid. 
     Specifically binds: As used herein, the term “specifically binds” refers to the ability of a molecule to bind to a binding partner with a degree of affinity or avidity that enables the molecule to be used to distinguish the binding partner from an appropriate control in a binding assay or other binding context. With respect to an antibody, the term, “specifically binds”, refers to the ability of the antibody to bind to a specific antigen with a degree of affinity or avidity, compared with an appropriate reference antigen or antigens, that enables the antibody to be used to distinguish the specific antigen from others, e.g., to an extent that permits preferential targeting to certain cells, e.g., muscle cells, through binding to the antigen, as described herein. In some embodiments, an antibody specifically binds to a target if the antibody has a K D  for binding the target of at least about 10 −4  M, 10 −5  M, 10 −6  M, 10 −7  M, 10 −8  M, 10 −9  M, 10 −10  M, 10 −11  M, 10 −12  M, 10 −13  M, or less. In some embodiments, an antibody specifically binds to the transferrin receptor, e.g., an epitope of the apical domain of transferrin receptor. 
     Subject: As used herein, the term “subject” refers to a mammal. In some embodiments, a subject is non-human primate, or rodent. In some embodiments, a subject is a human. In some embodiments, a subject is a patient, e.g., a human patient that has or is suspected of having a disease. In some embodiments, the subject is a human patient who has or is suspected of having a disease resulting from a disease-associated-repeat expansion, e.g., in a DMPK allele. 
     Transferrin receptor: As used herein, the term, “transferrin receptor” (also known as TFRC, CD71, p90, TFR, or TFR1) refers to an internalizing cell surface receptor that binds transferrin to facilitate iron uptake by endocytosis. In some embodiments, a transferrin receptor may be of human (NCBI Gene ID 7037), non-human primate (e.g., NCBI Gene ID 711568 or NCBI Gene ID 102136007), or rodent (e.g., NCBI Gene ID 22042) origin. In addition, multiple human transcript variants have been characterized that encoded different isoforms of the receptor (e.g., as annotated under GenBank RefSeq Accession Numbers: NP_001121620.1, NP_003225.2, NP_001300894.1, and NP_001300895.1). 
     2′-modified nucleoside: As used herein, the terms “2′-modified nucleoside” and “2′-modified ribonucleoside” are used interchangeably and refer to a nucleoside having a sugar moiety modified at the 2′ position. In some embodiments, the 2′-modified nucleoside is a 2′-4′ bicyclic nucleoside, where the 2′ and 4′ positions of the sugar are bridged (e.g., via a methylene, an ethylene, or a (S)-constrained ethyl bridge). In some embodiments, the 2′-modified nucleoside is a non-bicyclic 2′-modified nucleoside, e.g., where the 2′ position of the sugar moiety is substituted. Non-limiting examples of 2′-modified nucleosides include: 2′-deoxy, 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), 2′-O—N-methylacetamido (2′-O-NMA), locked nucleic acid (LNA, methylene-bridged nucleic acid), ethylene-bridged nucleic acid (ENA), and (S)-constrained ethyl-bridged nucleic acid (cEt). In some embodiments, the 2′-modified nucleosides described herein are high-affinity modified nucleotides and oligonucleotides comprising the 2′-modified nucleotides have increased affinity to a target sequences, relative to an unmodified oligonucleotide. Examples of structures of 2′-modified nucleosides are provided below: 
     
       
         
         
             
             
         
       
     
     II. Complexes 
     Provided herein are complexes that comprise a targeting agent, e.g. an antibody, covalently linked to a molecular payload. In some embodiments, a complex comprises a muscle-targeting antibody covalently linked to a oligonucleotide. A complex may comprise an antibody that specifically binds a single antigenic site or that binds to at least two antigenic sites that may exist on the same or different antigens. 
     A complex may be used to modulate the activity or function of at least one gene, protein, and/or (e.g., and) nucleic acid. In some embodiments, the molecular payload present with a complex is responsible for the modulation of a gene, protein, and/or (e.g., and) nucleic acids. A molecular payload may be a small molecule, protein, nucleic acid, oligonucleotide, or any molecular entity capable of modulating the activity or function of a gene, protein, and/or (e.g., and) nucleic acid in a cell. In some embodiments, a molecular payload is an oligonucleotide that targets a disease-associated repeat in muscle cells. 
     In some embodiments, a complex comprises a muscle-targeting agent, e.g. an anti-transferrin receptor antibody, covalently linked to a molecular payload, e.g. an antisense oligonucleotide that targets a disease-associated repeat, e.g. DMPK allele. 
     A. Muscle-Targeting Agents 
     Some aspects of the disclosure provide muscle-targeting agents, e.g., for delivering a molecular payload to a muscle cell. In some embodiments, such muscle-targeting agents are capable of binding to a muscle cell, e.g., via specifically binding to an antigen on the muscle cell, and delivering an associated molecular payload to the muscle cell. In some embodiments, the molecular payload is bound (e.g., covalently bound) to the muscle targeting agent and is internalized into the muscle cell upon binding of the muscle targeting agent to an antigen on the muscle cell, e.g., via endocytosis. It should be appreciated that various types of muscle-targeting agents may be used in accordance with the disclosure. For example, the muscle-targeting agent may comprise, or consist of, a nucleic acid (e.g., DNA or RNA), a peptide (e.g., an antibody), a lipid (e.g., a microvesicle), or a sugar moiety (e.g., a polysaccharide). Exemplary muscle-targeting agents are described in further detail herein, however, it should be appreciated that the exemplary muscle-targeting agents provided herein are not meant to be limiting. 
     Some aspects of the disclosure provide muscle-targeting agents that specifically bind to an antigen on muscle, such as skeletal muscle, smooth muscle, or cardiac muscle. In some embodiments, any of the muscle-targeting agents provided herein bind to (e.g., specifically bind to) an antigen on a skeletal muscle cell, a smooth muscle cell, and/or (e.g., and) a cardiac muscle cell. 
     By interacting with muscle-specific cell surface recognition elements (e.g., cell membrane proteins), both tissue localization and selective uptake into muscle cells can be achieved. In some embodiments, molecules that are substrates for muscle uptake transporters are useful for delivering a molecular payload into muscle tissue. Binding to muscle surface recognition elements followed by endocytosis can allow even large molecules such as antibodies to enter muscle cells. As another example molecular payloads conjugated to transferrin or anti-transferrin receptor antibodies can be taken up by muscle cells via binding to transferrin receptor, which may then be endocytosed, e.g., via clathrin-mediated endocytosis. 
     The use of muscle-targeting agents may be useful for concentrating a molecular payload (e.g., oligonucleotide) in muscle while reducing toxicity associated with effects in other tissues. In some embodiments, the muscle-targeting agent concentrates a bound molecular payload in muscle cells as compared to another cell type within a subject. In some embodiments, the muscle-targeting agent concentrates a bound molecular payload in muscle cells (e.g., skeletal, smooth, or cardiac muscle cells) in an amount that is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, or 100 times greater than an amount in non-muscle cells (e.g., liver, neuronal, blood, or fat cells). In some embodiments, a toxicity of the molecular payload in a subject is reduced by at least 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, or 95% when it is delivered to the subject when bound to the muscle-targeting agent. 
     In some embodiments, to achieve muscle selectivity, a muscle recognition element (e.g., a muscle cell antigen) may be required. As one example, a muscle-targeting agent may be a small molecule that is a substrate for a muscle-specific uptake transporter. As another example, a muscle-targeting agent may be an antibody that enters a muscle cell via transporter-mediated endocytosis. As another example, a muscle targeting agent may be a ligand that binds to cell surface receptor on a muscle cell. It should be appreciated that while transporter-based approaches provide a direct path for cellular entry, receptor-based targeting may involve stimulated endocytosis to reach the desired site of action. 
     i. Muscle-Targeting Antibodies 
     In some embodiments, the muscle-targeting agent is an antibody. Generally, the high specificity of antibodies for their target antigen provides the potential for selectively targeting muscle cells (e.g., skeletal, smooth, and/or (e.g., and) cardiac muscle cells). This specificity may also limit off-target toxicity. Examples of antibodies that are capable of targeting a surface antigen of muscle cells have been reported and are within the scope of the disclosure. For example, antibodies that target the surface of muscle cells are described in Arahata K., et al. “Immunostaining of skeletal and cardiac muscle surface membrane with antibody against Duchenne muscular dystrophy peptide”  Nature  1988; 333: 861-3; Song K. S., et al. “Expression of caveolin-3 in skeletal, cardiac, and smooth muscle cells. Caveolin-3 is a component of the sarcolemma and co-fractionates with dystrophin and dystrophin-associated glycoproteins”  J Biol Chem  1996; 271: 15160-5; and Weisbart R. H. et al., “Cell type specific targeted intracellular delivery into muscle of a monoclonal antibody that binds myosin IIb”  Mol Immunol.  2003 March, 39(13):78309; the entire contents of each of which are incorporated herein by reference. 
     a. Anti-Transferrin Receptor Antibodies 
     Some aspects of the disclosure are based on the recognition that agents binding to transferrin receptor, e.g., anti-transferrin-receptor antibodies, are capable of targeting muscle cell. Transferrin receptors are internalizing cell surface receptors that transport transferrin across the cellular membrane and participate in the regulation and homeostasis of intracellular iron levels. Some aspects of the disclosure provide transferrin receptor binding proteins, which are capable of binding to transferrin receptor. Accordingly, aspects of the disclosure provide binding proteins (e.g., antibodies) that bind to transferrin receptor. In some embodiments, binding proteins that bind to transferrin receptor are internalized, along with any bound molecular payload, into a muscle cell. As used herein, an antibody that binds to a transferrin receptor may be referred to interchangeably as an, transferrin receptor antibody, an anti-transferrin receptor antibody, or an anti-TfR antibody. Antibodies that bind, e.g. specifically bind, to a transferrin receptor may be internalized into the cell, e.g. through receptor-mediated endocytosis, upon binding to a transferrin receptor. 
     It should be appreciated that anti-transferrin receptor antibodies may be produced, synthesized, and/or (e.g., and) derivatized using several known methodologies, e.g. library design using phage display. Exemplary methodologies have been characterized in the art and are incorporated by reference (Díez, P. et al. “High-throughput phage-display screening in array format”, Enzyme and microbial technology, 2015, 79, 34-41.; Christoph M. H. and Stanley, J. R. “Antibody Phage Display: Technique and Applications” J Invest Dermatol. 2014, 134:2.; Engleman, Edgar (Ed.) “Human Hybridomas and Monoclonal Antibodies.” 1985, Springer.). In other embodiments, an anti-transferrin receptor antibody has been previously characterized or disclosed. Antibodies that specifically bind to transferrin receptor are known in the art (see, e.g. U.S. Pat. No. 4,364,934, filed Dec. 4, 1979, “Monoclonal antibody to a human early thymocyte antigen and methods for preparing same”; U.S. Pat. No. 8,409,573, filed Jun. 14, 2006, “Anti-CD71 monoclonal antibodies and uses thereof for treating malignant tumor cells”; U.S. Pat. No. 9,708,406, filed May 20, 2014, “Anti-transferrin receptor antibodies and methods of use”; U.S. Pat. No. 9,611,323, filed Dec. 19, 2014, “Low affinity blood brain barrier receptor antibodies and uses therefor”; WO 2015/098989, filed Dec. 24, 2014, “Novel anti-Transferrin receptor antibody that passes through blood-brain barrier”; Schneider C. et al. “Structural features of the cell surface receptor for transferrin that is recognized by the monoclonal antibody OKT9.” J Biol Chem. 1982, 257:14, 8516-8522.; Lee et al. “Targeting Rat Anti-Mouse Transferrin Receptor Monoclonal Antibodies through Blood-Brain Barrier in Mouse” 2000, J Pharmacol. Exp. Ther., 292: 1048-1052.). 
     Provided herein, in some aspects, are new anti-TfR antibodies for use as the muscle targeting agents (e.g., in muscle targeting complexes). In some embodiments, the anti-TfR antibody described herein binds to transferrin receptor with high specificity and affinity. In some embodiments, the anti-TfR antibody described herein specifically binds to any extracellular epitope of a transferrin receptor or an epitope that becomes exposed to an antibody. In some embodiments, anti-TfR antibodies provided herein bind specifically to transferrin receptor from human, non-human primates, mouse, rat, etc. In some embodiments, anti-TfR antibodies provided herein bind to human transferrin receptor. In some embodiments, the anti-TfR antibody described herein binds to an amino acid segment of a human or non-human primate transferrin receptor, as provided in SEQ ID NOs: 242-245. In some embodiments, the anti-TfR antibody described herein binds to an amino acid segment corresponding to amino acids 90-96 of a human transferrin receptor as set forth in SEQ ID NO: 242, which is not in the apical domain of the transferrin receptor. 
     In some embodiments, an anti-TFR antibody specifically binds a TfR1 (e.g., a human or non-human primate TfR1) with binding affinity (e.g., as indicated by Kd) of at least about 10 4  M, 10 −5  M, 10 −6  M, 10 −7  M, 10 −8  M, 10 −9  M, 10 −10  M, 10 −11  M, 10 −12  M, 10 −13  M, or less. In some embodiments, the anti-TfR antibodies described herein binds to TfR1 with a KD of sub-nanomolar range. In some embodiments, the anti-TfR antibodies described herein selectively binds to transferrin receptor 1 (TfR1) but do not bind to transferrin receptor 2 (TfR2). In some embodiments, the anti-TfR antibodies described herein binds to human TfR1 and cyno TfR1 (e.g., with a Kd of 10 −7  M, 10 −8  M, 10 −9  M, 10 −10  M, 10 −11  M, 10 −12  M, 10 −13  M, or less), but does not bind to a mouse TfR1. The affinity and binding kinetics of the anti-TfR antibody can be tested using any suitable method including but not limited to biosensor technology (e.g., OCTET or BIACORE). In some embodiments, binding of any one of the anti-TfR antibody described herein does not complete with or inhibit transferrin binding to the TfR1. In some embodiments, binding of any one of the anti-TfR antibody described herein does not complete with or inhibit HFE-beta-2-microglobulin binding to the TfR1. 
     An example human transferrin receptor amino acid sequence, corresponding to NCBI sequence NP_003225.2 (transferrin receptor protein 1 isoform 1,  Homo sapiens ) is as follows: 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 242) 
               
               
                   
                 MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNSH 
               
               
                   
               
               
                   
                 VEMKLAVDEEENADNNTKANVTKPKRCSGSICYGT 
               
               
                   
               
               
                   
                 IAVIVFFLIGFMIGYLGYCKGVEPKTECERLAGTE 
               
               
                   
               
               
                   
                 SPVREEPGEDFPAARRLYWDDLKRKLSEKLDSTDF 
               
               
                   
               
               
                   
                 TGTIKLLNENSYVPREAGSQKDENLALYVENQFRE 
               
               
                   
               
               
                   
                 FKLSKVWRDQHFVKIQVKDSAQNSVIIVDKNGRLV 
               
               
                   
               
               
                   
                 YLVENPGGYVAYSKAATVTGKLVHANFGTKKDFED 
               
               
                   
               
               
                   
                 LYTPVNGSIVIVRAGKITFAEKVANAESLNAIGVL 
               
               
                   
               
               
                   
                 IYMDQTKFPIVNAELSFFGHAHLGTGDPYTPGFPS 
               
               
                   
               
               
                   
                 FNHTQFPPSRSSGLPNIPVQTISRAAAEKLFGNME 
               
               
                   
               
               
                   
                 GDCPSDWKTDSTCRMVTSESKNVKLTVSNVLKEIK 
               
               
                   
               
               
                   
                 ILNIFGVIKGFVEPDHYVVVGAQRDAWGPGAAKSG 
               
               
                   
               
               
                   
                 VGTALLLKLAQMFSDMVLKDGFQPSRSIIFASWSA 
               
               
                   
               
               
                   
                 GDFGSVGATEWLEGYLSSLHLKAFTYINLDKAVLG 
               
               
                   
               
               
                   
                 TSNFKVSASPLLYTLIEKTMQNVKHPVTGQFLYQD 
               
               
                   
               
               
                   
                 SNWASKVEKLTLDNAAFPFLAYSGIPAVSFCFCED 
               
               
                   
               
               
                   
                 TDYPYLGTTMDTYKELIERIPELNKVARAAAEVAG 
               
               
                   
               
               
                   
                 QFVIKLTHDVELNLDYERYNSQLLSFVRDLNQYRA 
               
               
                   
               
               
                   
                 DIKEMGLSLQWLYSARGDFFRATSRLTTDFGNAEK 
               
               
                   
               
               
                   
                 TDRFVMKKLNDRVMRVEYHFLSPYVSPKESPFRHV 
               
               
                   
               
               
                   
                 FWGSGSHTLPALLENLKLRKQNNGAFNETLFRNQL 
               
               
                   
               
               
                   
                 ALATWTIQGAANALSGDVWDIDNEF. 
               
            
           
         
       
     
     An example non-human primate transferrin receptor amino acid sequence, corresponding to NCBI sequence NP_001244232.1 (transferrin receptor protein 1,  Macaca  mulatta) is as follows: 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 243) 
               
               
                   
                 MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNSH 
               
               
                   
               
               
                   
                 VEMKLGVDEEENTDNNTKPNGTKPKRCGGNICYGT 
               
               
                   
               
               
                   
                 IAVIIFFLIGFMIGYLGYCKGVEPKTECERLAGTE 
               
               
                   
               
               
                   
                 SPAREEPEEDFPAAPRLYWDDLKRKLSEKLDTTDF 
               
               
                   
               
               
                   
                 TSTIKLLNENLYVPREAGSQKDENLALYIENQFRE 
               
               
                   
               
               
                   
                 FKLSKVWRDQHFVKIQVKDSAQNSVIIVDKNGGLV 
               
               
                   
               
               
                   
                 YLVENPGGYVAYSKAATVTGKLVHANFGTKKDFED 
               
               
                   
               
               
                   
                 LDSPVNGSIVIVRAGKITFAEKVANAESLNAIGVL 
               
               
                   
               
               
                   
                 IYMDQTKFPIVKADLSFFGHAHLGTGDPYTPGFPS 
               
               
                   
               
               
                   
                 FNHTQFPPSQSSGLPNIPVQTISRAAAEKLFGNME 
               
               
                   
               
               
                   
                 GDCPSDWKTDSTCKMVTSENKSVKLTVSNVLKETK 
               
               
                   
               
               
                   
                 ILNIFGVIKGFVEPDHYVVVGAQRDAWGPGAAKSS 
               
               
                   
               
               
                   
                 VGTALLLKLAQMFSDMVLKDGFQPSRSIIFASWSA 
               
               
                   
               
               
                   
                 GDFGSVGATEWLEGYLSSLHLKAFTYINLDKAVLG 
               
               
                   
               
               
                   
                 TSNFKVSASPLLYTLIEKTMQDVKHPVTGRSLYQD 
               
               
                   
               
               
                   
                 SNWASKVEKLTLDNAAFPFLAYSGIPAVSFCFCED 
               
               
                   
               
               
                   
                 TDYPYLGTTMDTYKELVERIPELNKVARAAAEVAG 
               
               
                   
               
               
                   
                 QFVIKLTHDTELNLDYERYNSQLLLFLRDLNQYRA 
               
               
                   
               
               
                   
                 DVKEMGLSLQWLYSARGDFFRATSRLTTDFRNAEK 
               
               
                   
               
               
                   
                 RDKFVMKKLNDRVMRVEYYFLSPYVSPKESPFRHV 
               
               
                   
               
               
                   
                 FWGSGSHTLSALLESLKLRRQNNSAFNETLFRNQL 
               
               
                   
               
               
                   
                 ALATWTIQGAANALSGDVWDIDNEF 
               
            
           
         
       
     
     An example non-human primate transferrin receptor amino acid sequence, corresponding to NCBI sequence XP_005545315.1 (transferrin receptor protein 1,  Macaca fascicularis ) is as follows: 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 244) 
               
               
                   
                 MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNSH 
               
               
                   
               
               
                   
                 VEMKLGVDEEENTDNNTKANGTKPKRCGGNICYGT 
               
               
                   
               
               
                   
                 IAVIIFFLIGFMIGYLGYCKGVEPKTECERLAGTE 
               
               
                   
               
               
                   
                 SPAREEPEEDFPAAPRLYWDDLKRKLSEKLDTTDF 
               
               
                   
               
               
                   
                 TSTIKLLNENLYVPREAGSQKDENLALYIENQFRE 
               
               
                   
               
               
                   
                 FKLSKVWRDQHFVKIQVKDSAQNSVIIVDKNGGLV 
               
               
                   
               
               
                   
                 YLVENPGGYVAYSKAATVTGKLVHANFGTKKDFED 
               
               
                   
               
               
                   
                 LDSPVNGSIVIVRAGKITFAEKVANAESLNAIGVL 
               
               
                   
               
               
                   
                 IYMDQTKFPIVKADLSFFGHAHLGTGDPYTPGFPS 
               
               
                   
               
               
                   
                 FNHTQFPPSQSSGLPNIPVQTISRAAAEKLFGNME 
               
               
                   
               
               
                   
                 GDCPSDWKTDSTCKMVTSENKSVKLTVSNVLKETK 
               
               
                   
               
               
                   
                 ILNIFGVIKGFVEPDHYVVVGAQRDAWGPGAAKSS 
               
               
                   
               
               
                   
                 VGTALLLKLAQMFSDMVLKDGFQPSRSIIFASWSA 
               
               
                   
               
               
                   
                 GDFGSVGATEWLEGYLSSLHLKAFTYINLDKAVLG 
               
               
                   
               
               
                   
                 TSNFKVSASPLLYTLIEKTMQDVKHPVTGRSLYQD 
               
               
                   
               
               
                   
                 SNWASKVEKLTLDNAAFPFLAYSGIPAVSFCFCED 
               
               
                   
               
               
                   
                 TDYPYLGTTMDTYKELVERIPELNKVARAAAEVAG 
               
               
                   
               
               
                   
                 QFVIKLTHDTELNLDYERYNSQLLLFLRDLNQYRA 
               
               
                   
               
               
                   
                 DVKEMGLSLQWLYSARGDFFRATSRLTTDFRNAEK 
               
               
                   
               
               
                   
                 RDKFVMKKLNDRVMRVEYYFLSPYVSPKESPFRHV 
               
               
                   
               
               
                   
                 FWGSGSHTLSALLESLKLRRQNNSAFNETLFRNQL 
               
               
                   
               
               
                   
                 ALATWTIQGAANALSGDVWDIDNEF. 
               
            
           
         
       
     
     An example mouse transferrin receptor amino acid sequence, corresponding to NCBI sequence NP_001344227.1 (transferrin receptor protein 1,  Mus musculus ) is as follows: 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 245) 
               
               
                   
                 MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNSH 
               
               
                   
               
               
                   
                 VEMKLAADEEENADNNMKASVRKPKRFNGRLCFAA 
               
               
                   
               
               
                   
                 IALVIFFLIGFMSGYLGYCKRVEQKEECVKLAETE 
               
               
                   
               
               
                   
                 ETDKSETMETEDVPTSSRLYWADLKTLLSEKLNSI 
               
               
                   
               
               
                   
                 EFADTIKQLSQNTYTPREAGSQKDESLAYYIENQF 
               
               
                   
               
               
                   
                 HEFKFSKVWRDEHYVKIQVKSSIGQNMVTIVQSNG 
               
               
                   
               
               
                   
                 NLDPVESPEGYVAFSKPTEVSGKLVHANFGTKKDF 
               
               
                   
               
               
                   
                 EELSYSVNGSLVIVRAGEITFAEKVANAQSFNAIG 
               
               
                   
               
               
                   
                 VLIYMDKNKFPVVEADLALFGHAHLGTGDPYTPGF 
               
               
                   
               
               
                   
                 PSFNHTQFPPSQSSGLPNIPVQTISRAAAEKLFGK 
               
               
                   
               
               
                   
                 MEGSCPARWNIDSSCKLELSQNQNVKLIVKNVLKE 
               
               
                   
               
               
                   
                 RRILNIFGVIKGYEEPDRYVVVGAQRDALGAGVAA 
               
               
                   
               
               
                   
                 KSSVGTGLLLKLAQVFSDMISKDGFRPSRSIIFAS 
               
               
                   
               
               
                   
                 WTAGDFGAVGATEWLEGYLSSLHLKAFTYINLDKV 
               
               
                   
               
               
                   
                 VLGTSNFKVSASPLLYTLMGKIMQDVKHPVDGKSL 
               
               
                   
               
               
                   
                 YRDSNWISKVEKLSFDNAAYPFLAYSGIPAVSFCF 
               
               
                   
               
               
                   
                 CEDADYPYLGTRLDTYEALTQKVPQLNQMVRTAAE 
               
               
                   
               
               
                   
                 VAGQLIIKLTHDVELNLDYEMYNSKLLSFMKDLNQ 
               
               
                   
               
               
                   
                 FKTDIRDMGLSLQWLYSARGDYFRATSRLTTDFHN 
               
               
                   
               
               
                   
                 AEKTNRFVMREINDRIMKVEYHFLSPYVSPRESPF 
               
               
                   
               
               
                   
                 RHIFWGSGSHTLSALVENLKLRQKNITAFNETLFR 
               
               
                   
               
               
                   
                 NQLALATWTIQGVANALSGDIWNIDNEF 
               
            
           
         
       
     
     In some embodiments, an anti-transferrin receptor antibody binds to an amino acid segment of the receptor as follows: 
                            (SEQ ID NO: 730)           FVKIQVKDSAQNSVIIVDKNGRLVYLVENPGGYVA                   YSKAATVTGKLVHANFGTKKDFEDLYTPVNGSIVI                   VRAGKITFAEKVANAESLNAIGVLIYMDQTKFPIV                   NAELSFFGHAHLGTGDPYTPGFPSFNHTQFPPSRS                   SGLPNIPVQTISRAAAEKLFGNMEGDCPSDWKTDS                   TCRMVTSESKNVKLTVSNVLKE            
and does not inhibit the binding interactions between transferrin receptors and transferrin and/or (e.g., and) human hemochromatosis protein (also known as HFE). In some embodiments, the anti-transferrin receptor antibody described herein does not bind an epitope in SEQ ID NO: 730.
 
     Appropriate methodologies may be used to obtain and/or (e.g., and) produce antibodies, antibody fragments, or antigen-binding agents, e.g., through the use of recombinant DNA protocols. In some embodiments, an antibody may also be produced through the generation of hybridomas (see, e.g., Kohler, G and Milstein, C. “Continuous cultures of fused cells secreting antibody of predefined specificity” Nature, 1975, 256: 495-497). The antigen-of-interest may be used as the immunogen in any form or entity, e.g., recombinant or a naturally occurring form or entity. Hybridomas are screened using standard methods, e.g. ELISA screening, to find at least one hybridoma that produces an antibody that targets a particular antigen. Antibodies may also be produced through screening of protein expression libraries that express antibodies, e.g., phage display libraries. Phage display library design may also be used, in some embodiments, (see, e.g. U.S. Pat. No. 5,223,409, filed Mar. 1, 1991, “Directed evolution of novel binding proteins”; WO 1992/18619, filed Apr. 10, 1992, “Heterodimeric receptor libraries using phagemids”; WO 1991/17271, filed May 1, 1991, “Recombinant library screening methods”; WO 1992/20791, filed May 15, 1992, “Methods for producing members of specific binding pairs”; WO 1992/15679, filed Feb. 28, 1992, and “Improved epitope displaying phage”). In some embodiments, an antigen-of-interest may be used to immunize a non-human animal, e.g., a rodent or a goat. In some embodiments, an antibody is then obtained from the non-human animal, and may be optionally modified using a number of methodologies, e.g., using recombinant DNA techniques. Additional examples of antibody production and methodologies are known in the art (see, e.g. Harlow et al. “Antibodies: A Laboratory Manual”, Cold Spring Harbor Laboratory, 1988.). 
     In some embodiments, an antibody is modified, e.g., modified via glycosylation, phosphorylation, sumoylation, and/or (e.g., and) methylation. In some embodiments, an antibody is a glycosylated antibody, which is conjugated to one or more sugar or carbohydrate molecules. In some embodiments, the one or more sugar or carbohydrate molecule are conjugated to the antibody via N-glycosylation, O-glycosylation, C-glycosylation, glypiation (GPI anchor attachment), and/or (e.g., and) phosphoglycosylation. In some embodiments, the one or more sugar or carbohydrate molecules are monosaccharides, disaccharides, oligosaccharides, or glycans. In some embodiments, the one or more sugar or carbohydrate molecule is a branched oligosaccharide or a branched glycan. In some embodiments, the one or more sugar or carbohydrate molecule includes a mannose unit, a glucose unit, an N-acetylglucosamine unit, an N-acetylgalactosamine unit, a galactose unit, a fucose unit, or a phospholipid unit. In some embodiments, there are about 1-10, about 1-5, about 5-10, about 1-4, about 1-3, or about 2 sugar molecules. In some embodiments, a glycosylated antibody is fully or partially glycosylated. In some embodiments, an antibody is glycosylated by chemical reactions or by enzymatic means. In some embodiments, an antibody is glycosylated in vitro or inside a cell, which may optionally be deficient in an enzyme in the N- or O-glycosylation pathway, e.g. a glycosyltransferase. In some embodiments, an antibody is functionalized with sugar or carbohydrate molecules as described in International Patent Application Publication WO2014065661, published on May 1, 2014, entitled, “Modified antibody, antibody-conjugate and process for the preparation thereof”. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VL domain and/or (e.g., and) VH domain of any one of the anti-TfR antibodies selected from Table 2, and comprises a constant region comprising the amino acid sequences of the constant regions of an IgG, IgE, IgM, IgD, IgA or IgY immunoglobulin molecule, any class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2), or any subclass (e.g., IgG2a and IgG2b) of immunoglobulin molecule. Non-limiting examples of human constant regions are described in the art, e.g., see Kabat E A et al., (1991) supra. 
     The heavy chain and light chain variable domain and CDR sequences of examples of anti-TfR antibodies are provided in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Examples of anti-TfR1 antibodies 
               
               
                 (CDRs according to the IMGT® definition) 
               
            
           
           
               
               
               
            
               
                 Ab 
                 CDRs 
                 Variable domains 
               
               
                   
               
               
                 3-A4 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFNIKDDY 
                 EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQ 
               
               
                   
                 (SEQ ID NO: 1) 
                 RPEQGLEWIGWIDPENGDTEYASKFQDKATVTADTSSNTA 
               
               
                   
                 CDR-H2: 
                 YLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS 
               
               
                   
                 IDPENGDT 
                 (SEQ ID NO: 7) 
               
               
                   
                 (SEQ ID NO: 2) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 TLWLRRGLDY 
                   
               
               
                   
                 (SEQ ID NO: 3) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 KSLLHSNGYTY 
                 DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWF 
               
               
                   
                 (SEQ ID NO: 4) 
                 LQRPGQSPQLLIYRMSNLASGVPDRFSGSGSGTAFTLRISR 
               
               
                   
                 CDR-L2: 
                 VEAEDVGVYYCMQHLEYPFTFGGGTKLEIK 
               
               
                   
                 RMS 
                 (SEQ ID NO: 8) 
               
               
                   
                 (SEQ ID NO: 5) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 MQHLEYPFT 
                   
               
               
                   
                 (SEQ ID NO: 6) 
                   
               
               
                   
               
               
                 3-M12 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYSITSGYY 
                 DVQLQESGPGLVKPSQSLSLTCSVTGYSITSGYYWNWIRQ 
               
               
                   
                 (SEQ ID NO: 9) 
                 FPGNKLEWMGYITFDGANNYNPSLKNRISITRDTSKNQFFL 
               
               
                   
                 CDR-H2: 
                 KLTSVTTEDTATYYCTRSSYDYDVLDYWGQGTTLTVSS 
               
               
                   
                 ITFDGAN 
                 (SEQ ID NO: 15) 
               
               
                   
                 (SEQ ID NO: 10) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 TRSSYDYDVLDY 
                   
               
               
                   
                 (SEQ ID NO: 11) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QDISNF 
                 DIQMTQTTSSLSASLGDRVTISCRASQDISNFLNWYQQRPD 
               
               
                   
                 (SEQ ID NO: 12) 
                 GTVKLLIYYTSRLHSGVPSRFSGSGSGTDFSLTVSNLEQEDI 
               
               
                   
                 CDR-L2: 
                 ATYFCQQGHTLPYTFGGGTKLEIK 
               
               
                   
                 YTS 
                 (SEQ ID NO: 16) 
               
               
                   
                 (SEQ ID NO: 13) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQGHTLPYT 
                   
               
               
                   
                 (SEQ ID NO: 14) 
                   
               
               
                   
               
               
                 5-H12 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYSFTDYC 
                 QIQLQQSGPELVRPGASVKISCKASGYSFTDYCINWVNQR 
               
               
                   
                 (SEQ ID NO: 17) 
                 PGQGLEWIGWIYPGSGNTRYSERFKGKATLTVDTSSNTAY 
               
               
                   
                 CDR-H2: 
                 MQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTV 
               
               
                   
                 IYPGSGNT 
                 SS 
               
               
                   
                 (SEQ ID NO: 18) 
                 (SEQ ID NO: 23) 
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 AREDYYPYHGMDY 
                   
               
               
                   
                 (SEQ ID NO: 
                   
               
               
                   
                 19) 
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 ESVDGYDNSF 
                 DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWY 
               
               
                   
                 (SEQ ID NO: 20) 
                 QQKPGQPPKLLIFRASNLESGIPARFSGSGSRTDFTLTINPV 
               
               
                   
                 CDR-L2: 
                 EAADVATYYCQQSSEDPWTFGGGTKLEIK 
               
               
                   
                 RAS 
                 (SEQ ID NO: 24) 
               
               
                   
                 (SEQ ID NO: 21) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQSSEDPWT 
                   
               
               
                   
                 (SEQ ID NO: 22) 
                   
               
               
                   
               
               
                 8-K6 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYTFTSYW 
                 QVHLQQPGAELVKPGASVKMSCKASGYTFTSYWITWVK 
               
               
                   
                 (SEQ ID NO: 25) 
                 QRPGQGLEWIGDIFPNSGRTNYDEKFKSKATLTVDTSSSTA 
               
               
                   
                 CDR-H2: 
                 YMQLSSLTSEDSAVYFCAREGNFGSLDYWGQGTTLTVSS 
               
               
                   
                 IFPNSGRT 
                 (SEQ ID NO: 31) 
               
               
                   
                 (SEQ ID NO: 26) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 AREGNFGSLDY 
                   
               
               
                   
                 (SEQ ID NO: 27) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 SNLNY 
                 QIVLTQSPAIMSASPGEKVTMTCSANSNLNYMNWYHQKS 
               
               
                   
                 (SEQ ID NO: 28) 
                 GTSPKRWIYDTSKLASGVPARFSASGSGTSYSLTISSMEAE 
               
               
                   
                 CDR-L2: 
                 DAATYYCQQWSRNPLTFGAGTRLELK 
               
               
                   
                 DTS 
                 (SEQ ID NO: 32) 
               
               
                   
                 (SEQ ID NO: 29) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQWSRNPLT 
                   
               
               
                   
                 (SEQ ID NO: 30) 
                   
               
               
                   
               
               
                 9-K23 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFSLNTYDVG 
                 QVTLKESGPGMLQPSQTLSLTCSFSGFSLNTYDVGVGWIR 
               
               
                   
                 (SEQ ID NO: 33) 
                 QPSGKGLEWLANIWWNDDKYYNSALKSRLTISKDTSNNQ 
               
               
                   
                 CDR-H2: 
                 VFLKISSVDTADTATYYCTLYSYDGGFAYWGQGTLVTVS 
               
               
                   
                 IWWNDDK 
                 A 
               
               
                   
                 (SEQ ID NO: 34) 
                 (SEQ ID NO: 39) 
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 TLYSYDGGFAY 
                   
               
               
                   
                 (SEQ ID NO: 35) 
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 SSVSSSY 
                 QIVLTQSPAIMSASLGERVTMTCTASSSVSSSYLHWYQQK 
               
               
                   
                 (SEQ ID NO: 36) 
                 PGSSPKLWIYSTSNLASGVPARFSGSGSGTSYSLTISSMEAE 
               
               
                   
                 CDR-L2: 
                 DAATYYCHQYHRSPYTFGGGTKLEIK 
               
               
                   
                 STS 
                 (SEQ ID NO: 40) 
               
               
                   
                 (SEQ ID NO: 37) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 HQYHRSPYT 
                   
               
               
                   
                 (SEQ ID NO: 38) 
                   
               
               
                   
               
               
                 3-E5 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYSFTGYN 
                 EIQMKQSGAELVKPGASVKISCKASGYSFTGYNMNWVKQ 
               
               
                   
                 (SEQ ID NO: 41) 
                 SHGKSLEWIGNINPYYGSTGYNQKFKGKATLTVDKSSSTA 
               
               
                   
                 CDR-H2: 
                 YMQLNSLTSEDSAVYYCARGDYGYDEGTWEAYWGQGTL 
               
               
                   
                 INPYYGST 
                 VTVSA 
               
               
                   
                 (SEQ ID NO: 42) 
                 (SEQ ID NO: 47) 
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARGDYGYDEGTWFAY 
                   
               
               
                   
                 (SEQ ID NO: 43) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLNSRTRKNY 
                 DIVMSQSPSSLAVSAGEKVTMSCKSSQSLLNSRTRKNYLA 
               
               
                   
                 (SEQ ID NO: 44) 
                 WYQQKPEQSPKLLIYWASTRESGVPDRITGSGSGTDETLT 
               
               
                   
                 CDR-L2: 
                 ISSVQAEDLAVYYCKQSYNLPITFGSGTKLEIK 
               
               
                   
                 WAS 
                 (SEQ ID NO: 48) 
               
               
                   
                 (SEQ ID NO: 45) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 KQSYNLPFT 
                   
               
               
                   
                 (SEQ ID NO: 46) 
                   
               
               
                   
               
               
                 6-D3 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYTFTRHW 
                 QVQLQQPGAELVKPGASVKMSCKASGYTITRHWITWVK 
               
               
                   
                 (SEQ ID NO: 49) 
                 QRPGQGLEWIGDIYPGSGRTNYNEKEKSTATLTVDTSSST 
               
               
                   
                 CDR-H2: 
                 AYMQLSSLTSEDSAVYYCARDGYLYINYFDYWGQGTTLT 
               
               
                   
                 IYPGSGRT 
                 VSS 
               
               
                   
                 (SEQ ID NO: 50) 
                 (SEQ ID NO: 54) 
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARDGYLYINYFDY 
                   
               
               
                   
                 (SEQ ID NO: 
                   
               
               
                   
                 51) 
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 SSVSF 
                 ENVLTQSPAIMSASPGEKVTMTCSASSSVSFMHWFQQKSS 
               
               
                   
                 (SEQ ID NO: 52) 
                 TSPKLWIYDTSKLASGVPGRFSGSGSGSSYSLTISSMAAED 
               
               
                   
                 CDR-L2: 
                 VATYYCFQGSGYPYTFGGGTKLEIK 
               
               
                   
                 DTS 
                 (SEQ ID NO: 55) 
               
               
                   
                 (SEQ ID NO: 29) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 FQGSGYPYT 
                   
               
               
                   
                 (SEQ ID NO: 53) 
                   
               
               
                   
               
               
                 4-O12 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFNIVDDY 
                 EVQLQQSGAELVRPGASVKLSCTASGFNIVDDYMHWVKQ 
               
               
                   
                 (SEQ ID NO: 56) 
                 RPEQGLEWIGWIYPENADTEYASKFQGKATITADTSSNTA 
               
               
                   
                 CDR-H2: 
                 YLQLSSLTSEDTAVYYCTTATGTGWFAYWGQGTLVTVSA 
               
               
                   
                 IYPENADT 
                 (SEQ ID NO: 62) 
               
               
                   
                 (SEQ ID NO: 57) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 TTATGTGWFAY 
                   
               
               
                   
                 (SEQ ID NO: 58) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLDSDGKTY 
                 DVVMTQTPLTLSVTIGQPASISCKSSQSLLDSDGKTYLNWL 
               
               
                   
                 (SEQ ID NO: 59) 
                 FQRPGQSPKRLIYLVSKLDSGVPDRFTGSGSGTDFTLKISR 
               
               
                   
                 CDR-L2: 
                 VETEDLGVYYCWQGTHFPWTFGGGAKLEIK 
               
               
                   
                 LVS 
                 (SEQ ID NO: 63) 
               
               
                   
                 (SEQ ID NO: 60) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 WQGTHFPWT 
                   
               
               
                   
                 (SEQ ID NO: 61) 
                   
               
               
                   
               
               
                 4-C5 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYTFSNYW 
                 QVQLQQSGAELMKPGASVKISCKATGYTFSNYWIEWVKQ 
               
               
                   
                 (SEQ ID NO: 64) 
                 RPGHGLEWIGEILPGSGSTNYNENFKGKATFTADTSSNTA 
               
               
                   
                 CDR-H2: 
                 YMQLSSLTSEDSAVYYCARRGAYGNFHYWGQGTTLTVSS 
               
               
                   
                 ILPGSGST 
                 (SEQ ID NO: 70) 
               
               
                   
                 (SEQ ID NO: 65) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARRGAYGNFHY 
                   
               
               
                   
                 (SEQ ID NO: 66) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 SSISSSN 
                 EIVLTQSPALMAASPGEKVTITCSVSSSISSSNLHWYQQKS 
               
               
                   
                 (SEQ ID NO: 67) 
                 ETSPKPWIYGTSNLASGVPVRFSGSGSGTSYSLTISSMEAE 
               
               
                   
                 CDR-L2: 
                 DAATYYCQQWRSYPYTFGGGTKLEIK 
               
               
                   
                 GTS 
                 (SEQ ID NO: 71) 
               
               
                   
                 (SEQ ID NO: 68) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQWRSYPYT 
                   
               
               
                   
                 (SEQ ID NO: 69) 
                   
               
               
                   
               
               
                 10-P5 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYTFTDYN 
                 EVQLQQFGAELVKPGASVKISCKASGYTFTDYNMAWVKE 
               
               
                   
                 (SEQ ID NO: 72) 
                 SHGKSLEWIGDINPNYDTTSYNQKFKGKATLTVDKSSSTA 
               
               
                   
                 CDR-H2: 
                 HMELRSLTSEGTAVYYCARSGYYGSSYYWHFDVWGTGT 
               
               
                   
                 INPNYDTT 
                 TVTVSS 
               
               
                   
                 (SEQ ID NO: 73) 
                 (SEQ ID NO: 77) 
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARSGYYGSSYYWHFDV 
                   
               
               
                   
                 (SEQ ID NO: 74) 
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLYSSNQKNY 
                 DIVMSQSPSSLAVSVGEKVTMSCKSSQSLLYSSNQKNYLA 
               
               
                   
                 (SEQ ID NO: 75) 
                 WYQQKPGQSPKLLIYWASTRESGVPDRFTGSGSGTDFTLT 
               
               
                   
                 CDR-L2: 
                 ISSVKAEDLAVYYCQQYYNYPFTFGSGTKLEIK(SEQID 
               
               
                   
                 WAS 
                 NO: 78) 
               
               
                   
                 (SEQ ID NO: 45) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQYYNYPFT 
                   
               
               
                   
                 (SEQ ID NO: 76) 
                   
               
               
                   
               
               
                 2-H19 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFNIKDYY 
                 EVQLQQSGAELVRSGASVKLSCTASGFNIKDYYMHWVKQ 
               
               
                   
                 (SEQ ID NO: 79) 
                 RPEQGLEWIGWIDPESGDTEYAPKFQGRATMTADTSSNTA 
               
               
                   
                 CDR-H2: 
                 YMQLSSLTSEDTAVYYCYGHDYRVDCWGQGTSVTVSS 
               
               
                   
                 IDPESGDT 
                 (SEQ ID NO: 85) 
               
               
                   
                 (SEQ ID NO: 80) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 YGHDYRVDC 
                   
               
               
                   
                 (SEQ ID NO: 81) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLVHSNGNTY 
                 DVVMTQTPLSLPVSLGDQASISCRSSQSLVHSNGNTYLHW 
               
               
                   
                 (SEQ ID NO: 82) 
                 YLQKPGQSPKLLIYKVSNRFSGVPDRFSGSGSGTDFTLKIS 
               
               
                   
                 CDR-L2: 
                 RVEAEDLGVYFCSQSTHIPWTFGGGTKLEIK (SEQ ID NO: 
               
               
                   
                 KVS 
                 86) 
               
               
                   
                 (SEQ ID NO: 83) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 SQSTHIPWT 
                   
               
               
                   
                 (SEQ ID NO: 84) 
                   
               
               
                   
               
               
                 3-F3 
                 CDR-H1: 
                 VH 
               
               
                   
                 GYTFTDYN 
                 EVQLQQFGAELVKPGASVKISCKASGYTFTDYNMGWVKQ 
               
               
                   
                 (SEQ ID NO: 72) 
                 SHGKSLEWIGDINPNYDSTSYTQKFKGKATLTVDKSSSTA 
               
               
                   
                 CDR-H2: 
                 YMELRSLTSEDTAVYYCARSGYYGSSYYWHFDVWGTGT 
               
               
                   
                 INPNYDST 
                 TVTVSS (SEQ ID NO: 89) 
               
               
                   
                 (SEQ ID NO: 87) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARSGYYGSSYYWHEDV 
                   
               
               
                   
                 (SEQ ID 
                   
               
               
                   
                 NO: 74) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLYSSNQKNY 
                 DIVMSQSPSSLAVSVGEKVTMSCKSSQSLLYSSNQKNYLA 
               
               
                   
                 (SEQ ID NO: 75) 
                 WYQQKPGQSPKLLIYWASTRESGVPDRFTGSGSGTDFTLT 
               
               
                   
                 CDR-L2: 
                 ISSVKAEDLAVYYCQQYYHYPFTFGSGTKLEIK (SEQ ID 
               
               
                   
                 WAS 
                 NO: 90) 
               
               
                   
                 (SEQ ID NO: 45) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQYYHYPFT 
                   
               
               
                   
                 (SEQ ID NO: 88) 
                   
               
               
                   
               
               
                 8-O17 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFSLTNYG 
                 QVQLKESGPGLV APSQSLSITCTVSGFSLTNYGVHWVRQP 
               
               
                   
                 (SEQ ID NO: 91) 
                 PGKGLEWLVVIWNDGSATYNSALESRLSISKDNSKSQVFL 
               
               
                   
                 CDR-H2: 
                 KMNSLQTDDTAMYYCARHESSNPFAYWGQGTLVTVSA 
               
               
                   
                 IWNDGSA 
                 (SEQ ID NO: 97) 
               
               
                   
                 (SEQ ID NO: 92) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARHESSNPFAY 
                   
               
               
                   
                 (SEQ ID NO: 93) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSIGTS 
                 DILLTQSPAILSVSPGERVSFSCRASQSIGTSIHWYQQRTNG 
               
               
                   
                 (SEQ ID NO: 94) 
                 SPRLLIKSASESIAGIPSRFSGSGSGTDFTLSINSVESEDIADY 
               
               
                   
                 CDR-L2: 
                 YCQQNNRWPYTFGGGTKLEIK (SEQ ID NO: 98) 
               
               
                   
                 SAS 
                   
               
               
                   
                 (SEQ ID NO: 95) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQNNRWPYT 
                   
               
               
                   
                 (SEQ ID NO: 96) 
                   
               
               
                   
               
               
                 3-M9 
                 CDR-H1: 
                 VH 
               
               
                   
                 DFNIKDDY 
                 EVQLQQSGAELVRPGASVKLSCTASDFNIKDDYIHWVKQ 
               
               
                   
                 (SEQ ID NO: 99) 
                 RPEQGLEWIGR1DPANGNTKYAPKFQDKATITADTSSNTA 
               
               
                   
                 CDR-H2: 
                 YLQLSSLTSEDTAVYYCALGYTYWGQGTTLTVSS 
               
               
                   
                 IDPANGNT 
                 (SEQ ID NO: 104) 
               
               
                   
                 (SEQ ID NO: 100) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ALGYTY 
                   
               
               
                   
                 (SEQ ID NO: 101) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLHSYGKTY 
                 DVVMTQTPLTLSVTIGQPASISCKSSQSLLHSYGKTYLNWL 
               
               
                   
                 (SEQ ID NO: 102) 
                 LQRPGQSPKLLIYLVSKLESGVPDRFSGSGSGTDFTLKISRV 
               
               
                   
                 CDR-L2: 
                 EAEDLGVYYCLQTTHFPQTFGGGTKLEIK (SEQ ID NO: 
               
               
                   
                 LVS 
                 105) 
               
               
                   
                 (SEQ ID NO: 60) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 LQTTHFPQT 
                   
               
               
                   
                 (SEQ ID NO: 103) 
                   
               
               
                   
               
               
                 10-H2 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFTFSDYG 
                 EVQLVESGGDLVKPGGSLKLSCAASGFTFSDYGMHWVRQ 
               
               
                   
                 (SEQ ID NO: 106) 
                 GPEKGLEWVAYINSGSSTIYYADTVKGRFTISRDNAKNTL 
               
               
                   
                 CDR-H2: 
                 FLQMTSLRSEDTAMYYCARPGDYDNYAMDYWGQGTSVT 
               
               
                   
                 INSGSSTI 
                 VSS (SEQ ID NO: 112) 
               
               
                   
                 (SEQ ID NO: 107) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARPGDYDNYAMDY 
                   
               
               
                   
                 (SEQ ID NO: 108) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QDVSVA 
                 D1VMTQSHKFLSTSVGDRVSITCKASQDVSVAVAWYQQK 
               
               
                   
                 (SEQ ID NO: 109) 
                 PGQSPKLLIYWAYTRHTGVPDRFTGSGSGTEYTLTISSVQA 
               
               
                   
                 CDR-L2: 
                 EDLALYYCQQHYNTPPWTFGGGTKLEIK 
               
               
                   
                 WAY 
                 (SEQ ID NO: 113) 
               
               
                   
                 (SEQ ID NO: 110) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQHYNTPPWT 
                   
               
               
                   
                 (SEQ ID NO: 111) 
                   
               
               
                   
               
               
                 4-J22 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFNIKDYY 
                 EVQLQQSGAELVRSGASVKLSCTASGFNIKDYYIHWVKQ 
               
               
                   
                 (SEQ ID NO: 79) 
                 RPEQGLEWIGWIDPENADTEYAPKFQGKATMTPDTSSNTA 
               
               
                   
                 CDR-H2: 
                 YLQLSSLTSEDTAVYYCYAWDYSMDYWGQGTSVTVSS 
               
               
                   
                 IDPENADT 
                 (SEQ ID NO: 117) 
               
               
                   
                 (SEQ ID NO: 114) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 YAWDYSMDY 
                   
               
               
                   
                 (SEQ ID NO: 115) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLVHSNGNTY 
                 DVVMTQTPLSLSVSLGDQASISCRSSQSLVHSNGNTYLHW 
               
               
                   
                 (SEQ ID NO: 82) 
                 YLQKPGQSPKLL1YKVSNRFSGVPDRFSGSGSGTDFILKISR 
               
               
                   
                 CDR-L2: 
                 VEAEDLGVYFCSQNTHVPYTFGGGTRLEIK (SEQ ID NO: 
               
               
                   
                 KVS 
                 118) 
               
               
                   
                 (SEQ ID NO: 83) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 SQNTHVPYT 
                   
               
               
                   
                 (SEQ ID NO: 116) 
                   
               
               
                   
               
               
                 9-D4 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFTPTDYG 
                 QVQLQQSGTELARPGASVKLSCKASGFTFTDYGINWVKQ 
               
               
                   
                 (SEQ ID NO: 119) 
                 RTGQGLEWIGEIYPSSGNSYYNEKFKAKATLTADKSSSTA 
               
               
                   
                 CDR-H2: 
                 YMELRSLTSEDSAVYFCARSTYYGSPIDYWGQGTTLTVSS 
               
               
                   
                 IYPSSGNS 
                 (SEQ ID NO: 124) 
               
               
                   
                 (SEQ ID NO: 120) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARSTYYGSPIDY 
                   
               
               
                   
                 (SEQ ID NO: 121) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QDVDTT 
                 DIVMTQSHKFMSTPVGDRVSITCKASQDVDTTVAWYQQK 
               
               
                   
                 (SEQ ID NO: 122) 
                 PGQSPKLUYWASTRQIGVPDRFTGSGSGTDFTLTISNVQSE 
               
               
                   
                 CDR-L2: 
                 DLADYFCQQYSTYPLTFGGGTKLEIK 
               
               
                   
                 WAS 
                 (SEQ ID NO: 125) 
               
               
                   
                 (SEQ ID NO: 45) 
                   
               
               
                   
                 CDR L3: 
                   
               
               
                   
                 QQYSTYPLT 
                   
               
               
                   
                 (SEQ ID NO: 123) 
                   
               
               
                   
               
               
                 8-D15 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFSLTSYA 
                 QVQLKESGPGLVAPSQSLSITCTVSGFSLTSYAITWVRQSP 
               
               
                   
                 (SEQ ID NO: 126) 
                 GKGLEWLGLIWTGGGTNYNSALKSRLSISKDNSKSQVFLK 
               
               
                   
                 CDR-H2: 
                 MNSLQTDDTARYYCARIYDGYYRYFDVWGTGTTVTVSS 
               
               
                   
                 IWTGGGT 
                 (SEQ ID NO: 132) 
               
               
                   
                 (SEQ ID NO: 127) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ARIYDGYYRYFDV 
                   
               
               
                   
                 (SEQ ID NO: 
                   
               
               
                   
                 128) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSVSND 
                 RIVLTQTPKFLLVSAGDRVTMTCKASQSVSNDVAWYQQK 
               
               
                   
                 (SEQ ID NO: 129) 
                 PGQSPKLLIYYASNRYTGVPDRFTGSGYGTDFTFTISTVQA 
               
               
                   
                 CDR-L2: 
                 EDLAVYFCQQDYSSPWTFGGGTKLEIK 
               
               
                   
                 YAS 
                 (SEQ ID NO: 133) 
               
               
                   
                 (SEQ ID NO: 130) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQDYSSPWT 
                   
               
               
                   
                 (SEQ ID NO: 131) 
                   
               
               
                   
               
               
                 4-H4 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFNIKDYY 
                 EVQLQQSGAELVRSGASVKLSCTASGFNIKDYYMHWVKQ 
               
               
                   
                 (SEQ ID NO: 79) 
                 RPEQGLDWIGWIDPENGDTEYAPKFQGKATMTADTSSNT 
               
               
                   
                 CDR-H2: 
                 AYLQLSSLTSEDTAVYYCNVLTMPTAYWGQGTLVTVSA 
               
               
                   
                 IDPENGDT 
                 (SEQ ID NO: 136) 
               
               
                   
                 (SEQ ID NO: 2) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 NVLTMPTAY 
                   
               
               
                   
                 (SEQ ID NO: 134) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 QSLLYSSNQKNY 
                 DIVMSQSPSSLAVSVGEKVIMSCKSSQSLLYSSNQKNYLA 
               
               
                   
                 (SEQ ID NO: 75) 
                 WYQQKPGQSPKLLIYWASTRESGVPDRFTGSGSGTDFTLT 
               
               
                   
                 CDR-L2: 
                 ISSVKAEDLAVYYCQQYYSYPYTFGCiCiTKLEIK 
               
               
                   
                 WAS 
                 (SEQ ID NO: 137) 
               
               
                   
                 (SEQ ID NO: 45) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 QQYYSYPYT 
                   
               
               
                   
                 (SEQ ID NO: 135) 
                   
               
               
                   
               
               
                 9-C4 
                 CDR-H1: 
                 VH 
               
               
                   
                 GFTFSSYG 
                 EVQLMESGGDLVKPGGSLKLSCAASGFTFSSYGLSWVRQ 
               
               
                   
                 (SEQ ID NO: 138) 
                 TPDKRLEWVATITSGGSYTYYPDSVKGRITISRDNARNTL 
               
               
                   
                 CDR-H2: 
                 YLQMFSLKSEDTAMYYCALWSLDYWGQGTTLTVSS 
               
               
                   
                 ITSGGSYT 
                 (SEQ ID NO: 143) 
               
               
                   
                 (SEQ ID NO: 139) 
                   
               
               
                   
                 CDR-H3: 
                   
               
               
                   
                 ALWSLDY 
                   
               
               
                   
                 (SEQ ID NO: 140) 
                   
               
               
                   
               
               
                   
                 CDR-L1: 
                 VL 
               
               
                   
                 SSLSY 
                 QIVLTQSPALMSASPGEKVTMTCSANSSLSYMHWYQQKPG 
               
               
                   
                 (SEQ ID NO: 141) 
                 TSPKRWIYDTSELASGVPARESGSGSGTSYSLTISSMEAED 
               
               
                   
                 CDR-L2: 
                 AATYYCHQRRSYPWTFGGGTKLEIK (SEQ ID NO: 144) 
               
               
                   
                 DTS (SEQ ID NO: 29) 
                   
               
               
                   
                 CDR-L3: 
                   
               
               
                   
                 HQRRSYPWT 
                   
               
               
                   
                 (SEQ ID NO: 142) 
               
               
                   
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibodies of the present disclosure comprises one or more of the CDR-H (e.g., CDR-H1, CDR-H2, and CDR-H3) amino acid sequences from any one of the anti-TfR antibodies selected from Table 2. In some embodiments, the anti-TfR antibodies of the present disclosure comprise the CDR-H1, CDR-H2, and CDR-H3 as provided for any one of the antibodies selected from Table 2. In some embodiments, the anti-TfR antibodies of the present disclosure comprises one or more of the CDR-L (e.g., CDR-L1, CDR-L2, and CDR-L3) amino acid sequences from any one of the anti-TfR antibodies selected from Table 2. In some embodiments, the anti-TfR antibodies of the present disclosure comprise the CDR-L1, CDR-L2, and CDR-L3 as provided for any one of the anti-TfR antibodies selected from Table 2. 
     In some embodiments, the anti-TfR antibodies of the present disclosure comprises the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 as provided for any one of the anti-TfR antibodies selected from Table 2. In some embodiments, antibody heavy and light chain CDR3 domains may play a particularly important role in the binding specificity/affinity of an antibody for an antigen. Accordingly, the anti-TfR antibodies of the disclosure may include at least the heavy and/or (e.g., and) light chain CDR3s of any one of the anti-TfR antibodies selected from Table 2. 
     In some examples, any of the anti-TfR antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any of the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and/or (e.g., and) CDR-L3 sequences from one of the anti-TfR antibodies selected from Table 2. In some embodiments, the position of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary by one, two, three, four, five, or six amino acid positions so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). For example, in some embodiments, the position defining a CDR of any antibody described herein can vary by shifting the N-terminal and/or (e.g., and) C-terminal boundary of the CDR by one, two, three, four, five, or six amino acids, relative to the CDR position of any one of the antibodies described herein, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). In another embodiment, the length of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary (e.g., be shorter or longer) by one, two, three, four, five, or more amino acids, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). 
     Accordingly, in some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids shorter than one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids longer than one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). Any method can be used to ascertain whether immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained, for example, using binding assays and conditions described in the art. 
     In some examples, any of the anti-TfR antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any one of the anti-TfR antibodies selected from Table 2. For example, the antibodies may include one or more CDR sequence(s) from any of the anti-TfR antibodies selected from Table 2 containing up to 5, 4, 3, 2, or 1 amino acid residue variations as compared to the corresponding CDR region in any one of the CDRs provided herein (e.g., CDRs from any of the anti-TfR antibodies selected from Table 2) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, any of the amino acid variations in any of the CDRs provided herein may be conservative variations. Conservative variations can be introduced into the CDRs at positions where the residues are not likely to be involved in interacting with a transferrin receptor protein (e.g., a human transferrin receptor protein), for example, as determined based on a crystal structure. Some aspects of the disclosure provide anti-TfR antibodies that comprise one or more of the heavy chain variable (VH) and/or (e.g., and) light chain variable (VL) domains provided herein. In some embodiments, any of the VH domains provided herein include one or more of the CDR-H sequences (e.g., CDR-H1, CDR-H2, and CDR-H3) provided herein, for example, any of the CDR-H sequences provided in any one of the anti-TfR selected from Table 2. In some embodiments, any of the VL domains provided herein include one or more of the CDR-L sequences (e.g., CDR-L1, CDR-L2, and CDR-L3) provided herein, for example, any of the CDR-L sequences provided in any one of the anti-TfR antibodies selected from Table 2. 
     In some embodiments, the anti-TfR antibodies of the disclosure include any antibody that includes a heavy chain variable domain and/or (e.g., and) a light chain variable domain of any one of the anti-TfR antibodies selected from Table 2, and variants thereof. In some embodiments, anti-TfR antibodies of the disclosure include any antibody that includes the heavy chain variable and light chain variable pairs of any anti-TfR antibodies selected from Table 2. 
     Aspects of the disclosure provide anti-TfR antibodies having a heavy chain variable (VH) and/or (e.g., and) a light chain variable (VL) domain amino acid sequence homologous to any of those described herein. In some embodiments, the anti-TfR antibody comprises a heavy chain variable sequence or a light chain variable sequence that is at least 75% (e.g., 80%, 85%, 90%, 95%, 98%, or 99%) identical to the heavy chain variable sequence and/or any light chain variable sequence of any one of the anti-TfR antibodies selected from Table 2. In some embodiments, the homologous heavy chain variable and/or (e.g., and) a light chain variable amino acid sequences do not vary within any of the CDR sequences provided herein. For example, in some embodiments, the degree of sequence variation (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) may occur within a heavy chain variable and/or (e.g., and) a light chain variable sequence excluding any of the CDR sequences provided herein. In some embodiments, any of the anti-TfR antibodies provided herein comprise a heavy chain variable sequence and a light chain variable sequence that comprises a framework sequence that is at least 75%, 80%, 85%, 90%, 95%, 98%, or 99% identical to the framework sequence of any anti-TfR antibodies selected from Table 2. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 1 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 2 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 3 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 4 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the IMGT definition system). 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having the amino acid sequence of SEQ ID NO: 1; a CDR-H2 having the amino acid sequence of SEQ ID NO: 2 with an amino acid substitution at position 5 (e.g., the asparagine at position 5 is substituted, e.g., with any one of Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), His (H), Ser (S), Thr (T), Tyr (Y), Cys (C), Trp (W), Met (M), Ala (A), Ile (I), Leu (L), Phe (F), Val (V), Pro (P), Gly (G)); and a CDR-H3 having the amino acid sequence of SEQ ID NO: 3. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having the amino acid sequence of SEQ ID NO: 4; a CDR-L2 having the amino acid sequence of SEQ ID NO: 5; and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6. In some embodiments, the amino acid substitution at position 5 of the CDR-H2 as set forth in SEQ ID NO: 2 is N5T or N5S. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having the amino acid sequence of SEQ ID NO: 1; a CDR-H2 having the amino acid sequence of SEQ ID NO: 731 or SEQ ID NO: 80; and a CDR-H3 having the amino acid sequence of SEQ ID NO: 3. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having the amino acid sequence of SEQ ID NO: 4; a CDR-L2 having the amino acid sequence of SEQ ID NO: 5; and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid H1 having the amino acid sequence of SEQ ID NO: 1, CDR-H2 having the amino acid sequence of SEQ ID NO: 2, SEQ ID NO: 731 or SEQ ID NO: 80, and CDR-H3 having the amino acid sequence of SEQ ID NO: 3. “Collectively,” as used anywhere in the present disclosure, means that the total number of amino acid variations in all of the three heavy chain CDRs is within the defined range. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 4, CDR-L2 having the amino acid sequence of SEQ ID NO: 5, and CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 1, CDR-H2 having the amino acid sequence of SEQ ID NO: 2, SEQ ID NO: 731 or SEQ ID NO: 80, and CDR-H3 having the amino acid sequence of SEQ ID NO: 3. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 4, CDR-L2 having the amino acid sequence of SEQ ID NO: 5, and CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 1; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 2, SEQ ID NO: 731 or SEQ ID NO: 80; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 3. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 4; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 5; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH as set forth in SEQ ID NO: 7 with an amino acid substitution at position 55 (e.g., the asparagine at position 55 is substituted, e.g., with any one of Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), His (H), Ser (S), Thr (T), Tyr (Y), Cys (C), Trp (W), Met (M), Ala (A), Ile (I), Leu (L), Phe (F), Val (V), Pro (P), Gly (G)). Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL as set forth in SEQ ID NO: 8. In some embodiments, the amino acid substitution at position 55 of the VH as set forth in SEQ ID NO: 7 is N55T or N55S. Amino acid position 55 in SEQ ID NO: 7 is assigned a number 54 when the VH set forth in SEQ ID NO: 7 is annotated using the Kabat numbering system. When N54T or N54S is referred to herein, it is referring to the mutations using the Kabat numbering system. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid substitution at position 64 relative to SEQ ID NO: 7. In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising a Met at a position corresponding to position 64 of SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, 98%, 99%, or 100%) identical to the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 9 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 10 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 11 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 12 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 9, CDR-H2 having the amino acid sequence of SEQ ID NO: 10, and CDR-H3 having the amino acid sequence of SEQ ID NO: 11. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 12, CDR-L2 having the amino acid sequence of SEQ ID NO: 13, and CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 9, CDR-H2 having the amino acid sequence of SEQ ID NO: 10, and CDR-H3 having the amino acid sequence of SEQ ID NO: 11. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 12, CDR-L2 having the amino acid sequence of SEQ ID NO: 13, and CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 9; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 10; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 11. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 12; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 13; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 17 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 18 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 19 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 20 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the IMGT definition system). 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having the amino acid sequence of SEQ ID NO: 17 with an amino acid substitution at position 8 (e.g., the cysteine at position 8 is substituted, e.g., with any one of Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), His (H), Ser (S), Thr (T), Tyr (Y), Asn (N), Trp (W), Met (M), Ala (A), Ile (I), Leu (L), Phe (F), Val (V), Pro (P), Gly (G)); a CDR-H2 having the amino acid sequence of SEQ ID NO: 18; and a CDR-H3 having the amino acid sequence of SEQ ID NO: 19. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having the amino acid sequence of SEQ ID NO: 20; a CDR-L2 having the amino acid sequence of SEQ ID NO: 21; and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22. In some embodiments, the amino acid substitution at position 8 of the CDR-H1 as set forth in SEQ ID NO: 17 is C8D or C8Y. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having the amino acid sequence of SEQ ID NO: 735 or SEQ ID NO: 737; a CDR-H2 having the amino acid sequence of SEQ ID NO: 18; and a CDR-H3 having the amino acid sequence of SEQ ID NO: 19. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having the amino acid sequence of SEQ ID NO: 20; a CDR-L2 having the amino acid sequence of SEQ ID NO: 21; and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737, CDR-H2 having the amino acid sequence of SEQ ID NO: 18, and CDR-H3 having the amino acid sequence of SEQ ID NO: 19. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 20, CDR-L2 having the amino acid sequence of SEQ ID NO: 21, and CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737, CDR-H2 having the amino acid sequence of SEQ ID NO: 18, and CDR-H3 having the amino acid sequence of SEQ ID NO: 19. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 20, CDR-L2 having the amino acid sequence of SEQ ID NO: 21, and CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 18; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 19. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 20; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 21; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH as set forth in SEQ ID NO: 23 with an amino acid substitution at position 33 (e.g., the cysteine at position 33 is substituted, e.g., with any one of Arg (R), Lys (K), Asp (D), Glu (E), Gln (Q), His (H), Ser (S), Thr (T), Tyr (Y), Asn (N), Trp (W), Met (M), Ala (A), Ile (I), Leu (L), Phe (F), Val (V), Pro (P), Gly (G)). Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL as set forth in SEQ ID NO: 24. In some embodiments, the amino acid substitution at position 33 of the VH as set forth in SEQ ID NO: 23 is C33D or C33Y. Amino acid 33 in SEQ ID NO: 23 is assigned a number 33 when the VH set forth in SEQ ID NO: 23 is annotated with the Kabat numbering system. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 31. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 32. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 25 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 26 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 27 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 28 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 29 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 30 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 25, CDR-H2 having the amino acid sequence of SEQ ID NO: 26, and CDR-H3 having the amino acid sequence of SEQ ID NO: 27. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 28, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 30. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 25, CDR-H2 having the amino acid sequence of SEQ ID NO: 26, and CDR-H3 having the amino acid sequence of SEQ ID NO: 27. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 28, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 30. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 25; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 26; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 27. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 28; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 29; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 30. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 31. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 32. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 31. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 32. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 31. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 32. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 39. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 40. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 33 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 34 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 35 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 36 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 37 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 38 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 33, CDR-H2 having the amino acid sequence of SEQ ID NO: 34, and CDR-H3 having the amino acid sequence of SEQ ID NO: 35. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 36, CDR-L2 having the amino acid sequence of SEQ ID NO: 37, and CDR-L3 having the amino acid sequence of SEQ ID NO: 38. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 33, CDR-H2 having the amino acid sequence of SEQ ID NO: 34, and CDR-H3 having the amino acid sequence of SEQ ID NO: 35. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 36, CDR-L2 having the amino acid sequence of SEQ ID NO: 37, and CDR-L3 having the amino acid sequence of SEQ ID NO: 38. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 33; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 34; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 35. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 36; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 37; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 38. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 39. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 40. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 39. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 40. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 39. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 40. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 47. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 48. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 41 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 42 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 43 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 44 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 45 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 46 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 41, CDR-H2 having the amino acid sequence of SEQ ID NO: 42, and CDR-H3 having the amino acid sequence of SEQ ID NO: 43. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 44, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 46. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 41, CDR-H2 having the amino acid sequence of SEQ ID NO: 42, and CDR-H3 having the amino acid sequence of SEQ ID NO: 43. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 44, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 46. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 41; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 42; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 43. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 44; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 45; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 46. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 47. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 48. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 47. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 48. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 47. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 48. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 54. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 55. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 49 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 50 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 51 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 52 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 29 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 53 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 49, CDR-H2 having the amino acid sequence of SEQ ID NO: 50, and CDR-H3 having the amino acid sequence of SEQ ID NO: 51. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 52, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 53. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 49, CDR-H2 having the amino acid sequence of SEQ ID NO: 50, and CDR-H3 having the amino acid sequence of SEQ ID NO: 51. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 52, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 53. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 49; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 50; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 51. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 52; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 29; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 53. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 54. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 55. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 54. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 55. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 54. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 55. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 62. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 63. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 56 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 57 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 58 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 59 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 60 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 61 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid H1 having the amino acid sequence of SEQ ID NO: 56, CDR-H2 having the amino acid sequence of SEQ ID NO: 57, and CDR-H3 having the amino acid sequence of SEQ ID NO: 58. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 59, CDR-L2 having the amino acid sequence of SEQ ID NO: 60, and CDR-L3 having the amino acid sequence of SEQ ID NO: 61. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 56, CDR-H2 having the amino acid sequence of SEQ ID NO: 57, and CDR-H3 having the amino acid sequence of SEQ ID NO: 58. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 59, CDR-L2 having the amino acid sequence of SEQ ID NO: 60, and CDR-L3 having the amino acid sequence of SEQ ID NO: 61. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 56; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 57; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 58. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 59; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 60; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 61. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 62. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 63. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 62. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 63. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 62. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 63. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 70. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 71. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 64 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 65 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 66 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 67 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 68 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 69 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 64, CDR-H2 having the amino acid sequence of SEQ ID NO: 65, and CDR-H3 having the amino acid sequence of SEQ ID NO: 66. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 67, CDR-L2 having the amino acid sequence of SEQ ID NO: 68, and CDR-L3 having the amino acid sequence of SEQ ID NO: 69. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 64, CDR-H2 having the amino acid sequence of SEQ ID NO: 65, and CDR-H3 having the amino acid sequence of SEQ ID NO: 66. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 67, CDR-L2 having the amino acid sequence of SEQ ID NO: 68, and CDR-L3 having the amino acid sequence of SEQ ID NO: 69. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 64; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 65; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 66. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 67; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 68; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 69. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 70. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 71. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 70. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 71. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 70. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 71. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 77. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 78. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 72 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 73 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 74 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 75 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 45 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 76 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 72, CDR-H2 having the amino acid sequence of SEQ ID NO: 73, and CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 76. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 72, CDR-H2 having the amino acid sequence of SEQ ID NO: 73, and CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 76. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 72; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 73; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 45; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 76. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 77. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 78. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 77. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 78. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 77. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 78. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 85. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 86. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 79 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 80 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 81 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 82 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 83 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 84 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 80, and CDR-H3 having the amino acid sequence of SEQ ID NO: 81. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 82, CDR-L2 having the amino acid sequence of SEQ ID NO: 83, and CDR-L3 having the amino acid sequence of SEQ ID NO: 84. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 80, and CDR-H3 having the amino acid sequence of SEQ ID NO: 81. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 82, CDR-L2 having the amino acid sequence of SEQ ID NO: 83, and CDR-L3 having the amino acid sequence of SEQ ID NO: 84. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 80; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 81. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 82; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 83; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 84. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 85. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 86. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 85. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 86. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 85. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 86. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 89. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 90. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 72 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 87 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 74 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 75 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 45 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 88 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 72, CDR-H2 having the amino acid sequence of SEQ ID NO: 87, and CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 88. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 72, CDR-H2 having the amino acid sequence of SEQ ID NO: 87, and CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 88. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 72; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 87; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 74. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 45; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 88. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 89. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 90. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation)no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 89. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 90. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 89. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 90. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 97. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 98. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 91 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 92 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 93 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 94 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 95 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 96 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 91, CDR-H2 having the amino acid sequence of SEQ ID NO: 92, and CDR-H3 having the amino acid sequence of SEQ ID NO: 93. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 94, CDR-L2 having the amino acid sequence of SEQ ID NO: 95, and CDR-L3 having the amino acid sequence of SEQ ID NO: 96. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 91, CDR-H2 having the amino acid sequence of SEQ ID NO: 92, and CDR-H3 having the amino acid sequence of SEQ ID NO: 93. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 94, CDR-L2 having the amino acid sequence of SEQ ID NO: 95, and CDR-L3 having the amino acid sequence of SEQ ID NO: 96. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 91; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 92; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 93. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 94; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 95; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 96. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 97. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 98. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 97. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 98. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 97. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 98. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 104. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 105. 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 99, CDR-H2 having the amino acid sequence of SEQ ID NO: 100, and CDR-H3 having the amino acid sequence of SEQ ID NO: 101. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 102, CDR-L2 having the amino acid sequence of SEQ ID NO: 60, and CDR-L3 having the amino acid sequence of SEQ ID NO: 103. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 99, CDR-H2 having the amino acid sequence of SEQ ID NO: 100, and CDR-H3 having the amino acid sequence of SEQ ID NO: 101. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 102, CDR-L2 having the amino acid sequence of SEQ ID NO: 60, and CDR-L3 having the amino acid sequence of SEQ ID NO: 103. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 99; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 100; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 101. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 102; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 60; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 103. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 104. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 105. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 104. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 105. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 104. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 105. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 112. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 113. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 106 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 107 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 108 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 109 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 110 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 111 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 106, CDR-H2 having the amino acid sequence of SEQ ID NO: 107, and CDR-H3 having the amino acid sequence of SEQ ID NO: 108. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 109, CDR-L2 having the amino acid sequence of SEQ ID NO: 110, and CDR-L3 having the amino acid sequence of SEQ ID NO: 111. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 106, CDR-H2 having the amino acid sequence of SEQ ID NO: 107, and CDR-H3 having the amino acid sequence of SEQ ID NO: 108. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 109, CDR-L2 having the amino acid sequence of SEQ ID NO: 110, and CDR-L3 having the amino acid sequence of SEQ ID NO: 111. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 106; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 107; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 108. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 109; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 110; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 111. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 112. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 113. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 112. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 113. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 112. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 113. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 117. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 118. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 79 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 114 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 115 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 82 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 83 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 116 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 114, and CDR-H3 having the amino acid sequence of SEQ ID NO: 115. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 82, CDR-L2 having the amino acid sequence of SEQ ID NO: 83, and CDR-L3 having the amino acid sequence of SEQ ID NO: 116. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 114, and CDR-H3 having the amino acid sequence of SEQ ID NO: 115. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 82, CDR-L2 having the amino acid sequence of SEQ ID NO: 83, and CDR-L3 having the amino acid sequence of SEQ ID NO: 116. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 114; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 115. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 82; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 83; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 116. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 117. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 118. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 117. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 118. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 117. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 118. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 124. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 125. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 119 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 120 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 121 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 122 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 45 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 123 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 119, CDR-H2 having the amino acid sequence of SEQ ID NO: 120, and CDR-H3 having the amino acid sequence of SEQ ID NO: 121. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 122, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 123. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 119, CDR-H2 having the amino acid sequence of SEQ ID NO: 120, and CDR-H3 having the amino acid sequence of SEQ ID NO: 121. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 122, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 123. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 119; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 120; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 121. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 122; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 45; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 123. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 124. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 125. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 124. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 125. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 124. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 125. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 132. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 133. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 126 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 127 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 128 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 129 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 130 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 131 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 126, CDR-H2 having the amino acid sequence of SEQ ID NO: 127, and CDR-H3 having the amino acid sequence of SEQ ID NO: 128. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 129, CDR-L2 having the amino acid sequence of SEQ ID NO: 130, and CDR-L3 having the amino acid sequence of SEQ ID NO: 131. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 126, CDR-H2 having the amino acid sequence of SEQ ID NO: 127, and CDR-H3 having the amino acid sequence of SEQ ID NO: 128. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 129, CDR-L2 having the amino acid sequence of SEQ ID NO: 130, and CDR-L3 having the amino acid sequence of SEQ ID NO: 131. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 126; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 127; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 128. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 129; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 130; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 131. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 132. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 133. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 132. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 133. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 132. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 133. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 136. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 137. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 79 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 2 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 134 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 75 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 45 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 135 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 2, and CDR-H3 having the amino acid sequence of SEQ ID NO: 134. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 135. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 79, CDR-H2 having the amino acid sequence of SEQ ID NO: 2, and CDR-H3 having the amino acid sequence of SEQ ID NO: 134. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 75, CDR-L2 having the amino acid sequence of SEQ ID NO: 45, and CDR-L3 having the amino acid sequence of SEQ ID NO: 135. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 79; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 2; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 134. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 75; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 45; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 135. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 136. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 137. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 136. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 137. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 136. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 137. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 143. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 144. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 138 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 139 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 140 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 141 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 29 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 142 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 138, CDR-H2 having the amino acid sequence of SEQ ID NO: 139, and CDR-H3 having the amino acid sequence of SEQ ID NO: 140. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 141, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 142. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 138, CDR-H2 having the amino acid sequence of SEQ ID NO: 139, and CDR-H3 having the amino acid sequence of SEQ ID NO: 140. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 141, CDR-L2 having the amino acid sequence of SEQ ID NO: 29, and CDR-L3 having the amino acid sequence of SEQ ID NO: 142. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 138; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 139; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 140. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 141; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 29; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 142. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 143. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 144. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 143. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 144. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 143. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 144. 
     The CDRs of an antibody may have different amino acid sequences when different definition systems are used (e.g., the IMGT definition, the Kabat definition, or the Chothia definition). A definition system annotates each amino acid in a given antibody sequence (e.g., VH or VL sequence) with a number, and numbers corresponding to the heavy chain and light chain CDRs are provided in Table 3. The CDRs listed in Table 2 are defined in accordance with the IMGT definition. CDR sequences of examples of anti-TfR antibodies according to the different definition systems are provided in Table 4. One skilled in the art is able to derive the CDR sequences using the different numbering systems for the anti-TfR antibodies provided in Table 2. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 CDR Definitions 
               
            
           
           
               
               
               
               
            
               
                   
                 IMGT 1   
                 Kabat 2   
                 Chothia 3   
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 CDR-H1 
                 27-38 
                 31-35 
                 26-32 
               
               
                   
                 CDR-H2 
                 56-65 
                 50-65 
                 53-55 
               
               
                   
                 CDR-H3 
                    105-116/117 
                  95-102 
                  96-101 
               
               
                   
                 CDR-L1 
                 27-38 
                 24-34 
                 26-32 
               
               
                   
                 CDR-L2 
                 56-65 
                 50-56 
                 50-52 
               
               
                   
                 CDR-L3 
                    105-116/117 
                 89-97 
                 91-96 
               
               
                   
                   
               
               
                   
                   1 IMGT ®, the international ImMunoGeneTics information system ®, imgt.org, Lefranc, M.-P. et al., Nucleic Acids Res., 27: 209-212 (1999) 
               
               
                   
                   2 Kabat et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242 
               
               
                   
                   3 Chothia et al., J. Mol. Biol. 196: 901-917 (1987)) 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 CDR sequences of examples of anti-TfR antibodies according 
               
               
                 to different definition systems 
               
            
           
           
               
               
               
               
               
            
               
                   
                 No. 
                   
                   
                   
               
               
                   
                 system 
                 IMGT 
                 Kabat 
                 Chothia 
               
               
                   
               
               
                 3-A4 
                 CDR-H1 
                 GFNIKDDY (SEQ ID NO: 1) 
                 DDYMY (SEQ ID NO: 
                 GFNIKDD (SEQ ID NO: 
               
               
                   
                   
                   
                 145) 
                 150) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IDPENGDT (SEQ ID NO: 2) 
                 WIDPENGDTEYASKFQD 
                 ENG (SEQ ID NO: 151) 
               
               
                   
                   
                   
                 (SEQ ID NO: 146) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 TLWLRRGLDY (SEQ ID 
                 WLRRGLDY (SEQ ID 
                 LRRGLD (SEQ ID NO: 
               
               
                   
                   
                 NO: 3) 
                 NO: 147) 
                 152) 
               
               
                   
               
               
                   
                 CDR-L1 
                 KSLLHSNGYTY (SEQ ID 
                 RSSKSLLHSNGYTYLF 
                 SKSLLHSNGYTY(SEQ 
               
               
                   
                   
                 NO: 4) 
                 (SEQ ID NO: 148) 
                 ID NO: 153) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RMS (SEQ ID NO: 5) 
                 RMSNLAS (SEQ ID NO: 
                 RMS(SEQ ID NO: 5) 
               
               
                   
                   
                   
                 149) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 MQHLEYPFT (SEQ ID NO: 
                 MQHLEYPFT (SEQ ID 
                 HLEYPF (SEQ ID NO: 
               
               
                   
                   
                 6) 
                 NO: 6) 
                 154) 
               
               
                   
               
               
                 3-A4 
                 CDR-H1 
                 GFNIKDDY (SEQ ID NO: 1) 
                 DDYMY (SEQ ID NO: 
                 GFNIKDD (SEQ ID NO: 
               
               
                 Variant 1 
                   
                   
                 145) 
                 150) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IDPETGDT (SEQ ID NO: 
                 WIDPETGDTEYASKFQD 
                 ETG (SEQ ID NO: 739) 
               
               
                   
                   
                 731) 
                 (SEQ ID NO: 732) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 TLWLRRGLDY (SEQ ID 
                 WLRRGLDY (SEQ ID 
                 LRRGLD (SEQ ID NO: 
               
               
                   
                   
                 NO: 3) 
                 NO: 147) 
                 152) 
               
               
                   
               
               
                   
                 CDR-L1 
                 KSLLHSNGYTY (SEQ ID 
                 RSSKSLLHSNGYTYLF 
                 SKSLLHSNGYTY(SEQ 
               
               
                   
                   
                 NO: 4) 
                 (SEQ ID NO: 148) 
                 ID NO: 153) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RMS (SEQ ID NO: 5) 
                 RMSNLAS (SEQ ID NO: 
                 RMS(SEQ ID NO: 5) 
               
               
                   
                   
                   
                 149) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 MQHLEYPFT (SEQ ID NO: 
                 MQHLEYPFT (SEQ ID 
                 HLEYPF (SEQ ID NO: 
               
               
                   
                   
                 6) 
                 NO: 6) 
                 154) 
               
               
                   
               
               
                 3-A4 
                 CDR-H1 
                 GFNIKDDY (SEQ ID NO: 1) 
                 DDYMY (SEQ ID NO: 
                 GFNIKDD (SEQ ID NO: 
               
               
                 Variant 2 
                   
                   
                 145) 
                 150) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IDPESGDT (SEQ ID NO: 
                 WIDPESGDTEYASKFQD 
                 ESG (SEQ ID NO: 740) 
               
               
                   
                   
                 80) 
                 (SEQ ID NO: 734) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 TLWLRRGLDY (SEQ ID 
                 WLRRGLDY (SEQ ID 
                 LRRGLD (SEQ ID NO: 
               
               
                   
                   
                 NO: 3) 
                 NO: 147) 
                 152) 
               
               
                   
               
               
                   
                 CDR-L1 
                 KSLLHSNGYTY (SEQ ID 
                 RSSKSLLHSNGYTYLF 
                 SKSLLHSNGYTY(SEQ 
               
               
                   
                   
                 NO: 4) 
                 (SEQ ID NO: 148) 
                 ID NO: 153) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RMS (SEQ ID NO: 5) 
                 RMSNLAS (SEQ ID NO: 
                 RMS(SEQ ID NO: 5) 
               
               
                   
                   
                   
                 149) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 MQHLEYPFT (SEQ ID NO: 
                 MQHLEYPFT (SEQ ID 
                 HLEYPF (SEQ ID NO: 
               
               
                   
                   
                 6) 
                 NO: 6) 
                 154) 
               
               
                   
               
               
                 3-M12 
                 CDR-H1 
                 GYSITSGYY (SEQ ID NO: 
                 SGYYWN (SEQ ID NO: 
                 GYSITSGY (SEQ ID NO: 
               
               
                   
                   
                 9) 
                 155) 
                 160) 
               
               
                   
               
               
                   
                 CDR-H2 
                 ITFDGAN (SEQ ID NO: 10) 
                 YITFDGANNYNPSLKN 
                 FDG (SEQ ID NO: 161) 
               
               
                   
                   
                   
                 (SEQ ID NO: 156) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 TRSSYDYDVLDY (SEQ ID 
                 SSYDYDVLDY (SEQ ID 
                 SYDYDVLD (SEQ ID 
               
               
                   
                   
                 NO: 11) 
                 NO: 157) 
                 NO: 162) 
               
               
                   
               
               
                   
                 CDR-L1 
                 QDISNF (SEQ ID NO: 12) 
                 RASQDISNFLN (SEQ ID 
                 SQDISNF (SEQ ID NO: 
               
               
                   
                   
                   
                 NO: 158) 
                 163) 
               
               
                   
               
               
                   
                 CDR-L2 
                 YTS (SEQ ID NO: 13) 
                 YTSRLHS (SEQ ID NO: 
                 YTS (SEQ ID NO: 13) 
               
               
                   
                   
                   
                 159) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 QQGHTLPYT (SEQ ID NO: 
                 QQGHTLPYT (SEQ ID 
                 GHTLPY (SEQ ID NO: 
               
               
                   
                   
                 14) 
                 NO: 14) 
                 164) 
               
               
                   
               
               
                 5-H12 
                 CDR-H1 
                 GYSFTDYC (SEQ ID NO: 
                 DYCIN (SEQ ID NO: 165) 
                 GYSFTDY (SEQ ID NO: 
               
               
                   
                   
                 17) 
                   
                 170) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IYPGSGNT (SEQ ID NO: 
                 WIYPGSGNTRYSERFKG 
                 GSG 
               
               
                   
                   
                 18) 
                 (SEQ ID NO: 166) 
                 (SEQ ID NO: 171) 
               
               
                   
               
               
                   
                 CDR-H3 
                 AREDYYPYHGMDY (SEQ 
                 EDYYPYHGMDY (SEQ 
                 DYYPYHGMD (SEQ ID 
               
               
                   
                   
                 ID NO: 19) 
                 ID NO: 167) 
                 NO: 172) 
               
               
                   
               
               
                   
                 CDR-L1 
                 ESVDGYDNSF (SEQ ID 
                 RASES VDGYDNSFMH 
                 SESVDGYDNSF (SEQ ID 
               
               
                   
                   
                 NO: 20) 
                 (SEQ ID NO: 168) 
                 NO: 173) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RAS (SEQ ID NO: 21) 
                 RASNLES (SEQ ID NO: 
                 RAS (SEQ ID NO: 21) 
               
               
                   
                   
                   
                 169) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 QQSSEDPWT (SEQ ID NO: 
                 QQSSEDPWT (SEQ ID 
                 SSEDPW (SEQ ID NO: 
               
               
                   
                   
                 22) 
                 NO: 22) 
                 174) 
               
               
                   
               
               
                 5-H12 
                 CDR-H1 
                 GYSFTDYY (SEQ ID NO: 
                 DYYIN (SEQ ID NO: 736) 
                 GYSFTDY (SEQ ID NO: 
               
               
                 Variant 1 
                   
                 735) 
                   
                 170) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IYPGSGNT (SEQ ID NO: 
                 WIYPGSGNTRYSERFKG 
                 GSG (SEQ ID NO: 171) 
               
               
                   
                   
                 18) 
                 (SEQ ID NO: 166) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 AREDYYPYHGMDY (SEQ 
                 EDYYPYHGMDY (SEQ 
                 DYYPYHGMD (SEQ ID 
               
               
                   
                   
                 ID NO: 19) 
                 ID NO: 167) 
                 NO: 172) 
               
               
                   
               
               
                   
                 CDR-L1 
                 ESVDGYDNSF (SEQ ID 
                 RASES VDGYDNSFMH 
                 SESVDGYDNSF (SEQ ID 
               
               
                   
                   
                 NO: 20) 
                 (SEQ ID NO: 168) 
                 NO: 173) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RAS (SEQ ID NO: 21) 
                 RASNLES (SEQ ID NO: 
                 RAS (SEQ ID NO: 21) 
               
               
                   
                   
                   
                 169) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 QQSSEDPWT (SEQ ID NO: 
                 QQSSEDPWT (SEQ ID 
                 SSEDPW (SEQ ID NO: 
               
               
                   
                   
                 22) 
                 NO: 22) 
                 174) 
               
               
                   
               
               
                 5-H12 
                 CDR-H1 
                 GYSFTDYD (SEQ ID NO: 
                 DYDIN (SEQ ID NO: 738) 
                 GYSFTDY (SEQ ID NO: 
               
               
                 Variant 2 
                   
                 737) 
                   
                 170) 
               
               
                   
               
               
                   
                 CDR-H2 
                 IYPGSGNT (SEQ ID NO: 
                 WIYPGSGNTRYSERFKG 
                 GSG (SEQ ID NO: 171) 
               
               
                   
                   
                 18) 
                 (SEQ ID NO: 166) 
                   
               
               
                   
               
               
                   
                 CDR-H3 
                 AREDYYPYHGMDY (SEQ 
                 EDYYPYHGMDY (SEQ 
                 DYYPYHGMD (SEQ ID 
               
               
                   
                   
                 ID NO: 19) 
                 ID NO: 167) 
                 NO: 172) 
               
               
                   
               
               
                   
                 CDR-L1 
                 ESVDGYDNSF (SEQ ID 
                 RASES VDGYDNSFMH 
                 SESVDGYDNSF (SEQ ID 
               
               
                   
                   
                 NO: 20) 
                 (SEQ ID NO: 168) 
                 NO: 173) 
               
               
                   
               
               
                   
                 CDR-L2 
                 RAS (SEQ ID NO: 21) 
                 RASNLES (SEQ ID NO: 
                 RAS (SEQ ID NO: 21) 
               
               
                   
                   
                   
                 169) 
                   
               
               
                   
               
               
                   
                 CDR-L3 
                 QQSSEDPWT (SEQ ID NO: 
                 QQSSEDPWT (SEQ ID 
                 SSEDPW (SEQ ID NO: 
               
               
                   
                   
                 22) 
                 NO: 22) 
                 174) 
               
               
                   
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 145 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 147 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 148 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 149 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the Kabat definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 145, CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734, and CDR-H3 having the amino acid sequence of SEQ ID NO: 147. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 148, CDR-L2 having the amino acid sequence of SEQ ID NO: 149, and CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 145, CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734, and CDR-H3 having the amino acid sequence of SEQ ID NO: 147. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 148, CDR-L2 having the amino acid sequence of SEQ ID NO: 149, and CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 145; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 147. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 148; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 149; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 6. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 150 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 152 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 153 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 154 (according to the Chothia definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 150, CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740, and CDR-H3 having the amino acid sequence of SEQ ID NO: 152. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 153, CDR-L2 having the amino acid sequence of SEQ ID NO: 5, and CDR-L3 having the amino acid sequence of SEQ ID NO: 154. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 150, CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740, and CDR-H3 having the amino acid sequence of SEQ ID NO: 152. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 153, CDR-L2 having the amino acid sequence of SEQ ID NO: 5, and CDR-L3 having the amino acid sequence of SEQ ID NO: 154. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 150; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 152. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 153; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 5; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 154. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 155 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 156 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 157 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 158 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 159 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the Kabat definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 155, CDR-H2 having the amino acid sequence of SEQ ID NO: 156, and CDR-H3 having the amino acid sequence of SEQ ID NO: 157. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 158, CDR-L2 having the amino acid sequence of SEQ ID NO: 159, and CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 155, CDR-H2 having the amino acid sequence of SEQ ID NO: 156, and CDR-H3 having the amino acid sequence of SEQ ID NO: 157. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 158, CDR-L2 having the amino acid sequence of SEQ ID NO: 159, and CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 155; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 156; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 157. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 158; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 159; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 14. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 160 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 161 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 162 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 163 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 164 (according to the Chothia definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variation (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 160, CDR-H2 having the amino acid sequence of SEQ ID NO: 161, and CDR-H3 having the amino acid sequence of SEQ ID NO: 162. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 163, CDR-L2 having the amino acid sequence of SEQ ID NO: 13, and CDR-L3 having the amino acid sequence of SEQ ID NO: 164. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 160, CDR-H2 having the amino acid sequence of SEQ ID NO: 161, and CDR-H3 having the amino acid sequence of SEQ ID NO: 162. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 163, CDR-L2 having the amino acid sequence of SEQ ID NO: 13, and CDR-L3 having the amino acid sequence of SEQ ID NO: 164. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 160; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 161; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 162. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 163; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 13; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 164. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 166 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 167 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 168 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 169 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the Kabat definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738, CDR-H2 having the amino acid sequence of SEQ ID NO: 166, and CDR-H3 having the amino acid sequence of SEQ ID NO: 167. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 168, CDR-L2 having the amino acid sequence of SEQ ID NO: 169, and CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738, CDR-H2 having the amino acid sequence of SEQ ID NO: 166, and CDR-H3 having the amino acid sequence of SEQ ID NO: 167. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 168, CDR-L2 having the amino acid sequence of SEQ ID NO: 169, and CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 166; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 167. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 168; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 169; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 22. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 170 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 171 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 172 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 173 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 174 (according to the Chothia definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 170, CDR-H2 having the amino acid sequence of SEQ ID NO: 171, and CDR-H3 having the amino acid sequence of SEQ ID NO: 172. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 173, CDR-L2 having the amino acid sequence of SEQ ID NO: 21, and CDR-L3 having the amino acid sequence of SEQ ID NO: 174. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 170, CDR-H2 having the amino acid sequence of SEQ ID NO: 171, and CDR-H3 having the amino acid sequence of SEQ ID NO: 172. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 173, CDR-L2 having the amino acid sequence of SEQ ID NO: 21, and CDR-L3 having the amino acid sequence of SEQ ID NO: 174. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 170; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 171; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 172. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 173; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 21; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 174. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody (e.g., a humanized variant containing one or more CDRs of Table 2 or Table 4). In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 2 or Table 4, and comprises a humanized heavy chain variable region and/or (e.g., and) a humanized light chain variable region. 
     Humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, or rabbit having the desired specificity, affinity, and capacity. In some embodiments, Fv framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, the humanized antibody may comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences, but are included to further refine and optimize antibody performance. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region or domain (Fc), typically that of a human immunoglobulin. Antibodies may have Fc regions modified as described in WO 99/58572. Other forms of humanized antibodies have one or more CDRs (one, two, three, four, five, six) which are altered with respect to the original antibody, which are also termed one or more CDRs derived from one or more CDRs from the original antibody. Humanized antibodies may also involve affinity maturation. 
     Humanized antibodies and methods of making them are known, e.g., as described in Almagro et al., Front. Biosci. 13:1619-1633 (2008); Riechmann et al., Nature 332:323-329 (1988); Queen et al., Proc. Nat&#39;l Acad. Sci. USA 86:10029-10033 (1989); U.S. Pat. Nos. 5,821,337, 7,527,791, 6,982,321, and 7,087,409; Kashmiri et al., Methods 36:25-34 (2005); Padlan et al., Mol. Immunol. 28:489-498 (1991); Dall&#39;Acqua et al., Methods 36:43-60 (2005); Osbourn et al., Methods 36:61-68 (2005); and Klimka et al., Br. J. Cancer, 83:252-260 (2000), the contents of all of which are incorporated herein by reference. Human framework regions that may be used for humanization are described in e.g., Sims et al. J. Immunol. 151:2296 (1993); Carter et al. Proc. Natl. Acad. Sci. USA, 89:4285 (1992); Presta et al. J. Immunol., 151:2623 (1993); Almagro et al., Front. Biosci. 13:1619-1633 (2008)); Baca et al., J. Biol. Chem. 272:10678-10684 (1997); and Rosok et al., J Biol. Chem. 271:22611-22618 (1996), the contents of all of which are incorporated herein by reference. In some embodiments, humanization is achieved by grafting the CDRs (e.g., as shown in Table 2 or Table 4) into the IGKV1-NL1*01 and IGHV1-3*01 human variable domains. 
     In some embodiments, a humanized VH framework or VL framework is a consensus human framework. In some embodiments, a consensus humanized framework can represent the most commonly occurring amino acid residue in a selection of human immunoglobulin VL or VH framework sequences. 
     In some embodiments, the consensus human VH framework regions suitable for use with heavy chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup III consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VH FR1: 
               
               
                   
                 (SEQ ID NO: 741) 
               
               
                   
                 EVQLVESGGGLVQPGGSLRLSCAAS; 
               
               
                   
               
               
                   
                 b) VH FR2: 
               
               
                   
                 (SEQ ID NO: 742) 
               
               
                   
                 WVRQAPGKGLEWV; 
               
               
                   
               
               
                   
                 c) VH FR3: 
               
               
                   
                 (SEQ ID NO: 743) 
               
               
                   
                 RFTISRDNSKNTLYLQMNSLRAEDTAVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VH FR4: 
               
               
                   
                 (SEQ ID NO: 744) 
               
               
                   
                 WGQGTLVTVSS. 
               
            
           
         
       
     
     In some embodiments, the consensus human VH framework regions suitable for use with heavy chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup I consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VH FR1: 
               
               
                   
                 (SEQ ID NO: 745) 
               
               
                   
                 QVQLVQSGAEVKKPGASVKVSCKAS; 
               
               
                   
               
               
                   
                 b) VH FR2: 
               
               
                   
                 (SEQ ID NO: 746) 
               
               
                   
                 WVRQAPGQGLEWM; 
               
               
                   
               
               
                   
                 c) VH FR3: 
               
               
                   
                 (SEQ ID NO: 747) 
               
               
                   
                 RVTITADTSTSTAYMELSSLRSEDTAVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VH FR4: 
               
               
                   
                 (SEQ ID NO: 744) 
               
               
                   
                 WGQGTLVTVSS. 
               
            
           
         
       
     
     In some embodiments, the consensus human VH framework regions suitable for use with heavy chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup II consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VH FR1: 
               
               
                   
                 (SEQ ID NO: 749) 
               
               
                   
                 QVQLQESGPGLVKPSQTLSLTCTVS; 
               
               
                   
               
               
                   
                 b) VH FR2: 
               
               
                   
                 (SEQ ID NO: 750) 
               
               
                   
                 WIRQPPGKGLEWI; 
               
               
                   
               
               
                   
                 c) VH FR3: 
               
               
                   
                 (SEQ ID NO: 751) 
               
               
                   
                 RVTISVDTSKNQFSLKLSSVTAADTAVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VH FR4: 
               
               
                   
                 (SEQ ID NO: 744) 
               
               
                   
                 WGQGTLVTVSS. 
               
            
           
         
       
     
     In some embodiments, the consensus human VL framework regions suitable for use with light chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup I consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VL FR1: 
               
               
                   
                 (SEQ ID NO: 753) 
               
               
                   
                 DIQMTQSPSSLSASVGDRVTITC; 
               
               
                   
               
               
                   
                 b) VL FR2: 
               
               
                   
                 (SEQ ID NO: 754) 
               
               
                   
                 WYQQKPGKAPKLLIY; 
               
               
                   
               
               
                   
                 c) VL FR3: 
               
               
                   
                 (SEQ ID NO: 756) 
               
               
                   
                 GVPSRFSGSGSGTDFTLTISSLQPEDFATYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VL FR4: 
               
               
                   
                 (SEQ ID NO: 748) 
               
               
                   
                 FGQGTKVEIK. 
               
            
           
         
       
     
     In some embodiments, the consensus human VL framework regions suitable for use with light chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup II consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VL FR1: 
               
               
                   
                 (SEQ ID NO: 757) 
               
               
                   
                 DIVMTQSPLSLPVTPGEPASISC; 
               
               
                   
               
               
                   
                 b) VL FR2: 
               
               
                   
                 (SEQ ID NO: 758) 
               
               
                   
                 WYLQKPGQSPQLLIY; 
               
               
                   
               
               
                   
                 c) VL FR3: 
               
               
                   
                 (SEQ ID NO: 759) 
               
               
                   
                 GVPDRFSGSGSGTDFTLKISRVEAEDVGVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VL FR4: 
               
               
                   
                 (SEQ ID NO: 748) 
               
               
                   
                 FGQGTKVEIK. 
               
            
           
         
       
     
     In some embodiments, the consensus human VL framework regions suitable for use with light chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup III consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VL FR1: 
               
               
                   
                 (SEQ ID NO: 752) 
               
               
                   
                 DIVMTQSPDSLAVSLGERATINC; 
               
               
                   
               
               
                   
                 b) VL FR2: 
               
               
                   
                 (SEQ ID NO: 755) 
               
               
                   
                 WYQQKPGQPPKLLIY; 
               
               
                   
               
               
                   
                 c) VL FR3: 
               
               
                   
                 (SEQ ID NO: 760) 
               
               
                   
                 GVPDRFSGSGSGTDFTLTISSLQAEDFAVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VL FR4: 
               
               
                   
                 (SEQ ID NO: 748) 
               
               
                   
                 FGQGTKVEIK. 
               
            
           
         
       
     
     In some embodiments, the consensus human VL framework regions suitable for use with light chain CDRs in the humanized anti-TfR antibodies described herein include (subgroup IV consensus): 
     
       
         
           
               
               
            
               
                   
                 a) VL FR1: 
               
               
                   
                 (SEQ ID NO: 752) 
               
               
                   
                 DIVMTQSPDSLAVSLGERATINC; 
               
               
                   
               
               
                   
                 b) VL FR2: 
               
               
                   
                 (SEQ ID NO: 755) 
               
               
                   
                 WYQQKPGQPPKLLIY; 
               
               
                   
               
               
                   
                 c) VL FR3: 
               
               
                   
                 (SEQ ID NO: 760) 
               
               
                   
                 GVPDRFSGSGSGTDFTLTISSLQAEDFAVYYC; 
               
               
                   
                 and 
               
               
                   
               
               
                   
                 d) VL FR4: 
               
               
                   
                 (SEQ ID NO: 748) 
               
               
                   
                 FGQGTKVEIK. 
               
            
           
         
       
     
     In some embodiments, the humanized anti-TfR antibody of the present disclosure comprises humanized VH framework regions that collectively contain no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with any one of the consensus human VH framework region subgroups described herein. Alternatively or in addition (e.g., in addition), the humanized anti-TfR antibody of the present disclosure comprises humanized VL framework regions that collectively contain no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with any one of the consensus human VL framework region subgroups described herein. 
     In some embodiments, the humanized anti-TfR antibody of the present disclosure comprises humanized VH framework regions that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of the consensus human VH framework region subgroups described herein. Alternatively or in addition (e.g., in addition), the humanized anti-TfR antibody of the present disclosure comprises humanized VL framework regions that are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of the consensus human VL framework region subgroups described herein. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized variant comprising one or more amino acid variations (e.g., in the VH framework region) as compared with any one of the VHs listed in Table 2 or Table 4, and/or (e.g., and) one or more amino acid variations (e.g., in the VL framework region) as compared with any one of the VLs listed in Table 2 or Table 4. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH of any of the anti-TfR antibodies listed in Table 2. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL of any one of the anti-TfR antibodies listed in Table 2. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in any one of SEQ ID NOs: 7, 15, and 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in any one of SEQ ID NOs: 8, 16, and 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in any one of SEQ ID NOs: 7, 15, and 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in any one of SEQ ID NOs: 8, 16, and 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in any one of SEQ ID NOs: 7, 15, and 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in any one of SEQ ID NOs: 8, 16, and 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VH having one or more (e.g., 10-25) amino acid variations at positions 1, 2, 5, 9, 11, 12, 13, 17, 20, 23, 33, 38, 40, 41, 42, 43, 44, 45, 48, 49, 55, 67, 68, 70, 71, 72, 76, 77, 80, 81, 82, 84, 87, 88, 91, 95, 112, or 115 relative to the VH as set forth in any one of SEQ ID NOs: 7, 15, and 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a humanized antibody comprising a VL having one or more (e.g., 10-20) amino acid variations at positions 4, 7, 8, 9, 11, 15, 17, 18, 19, 22, 39, 41, 42, 43, 50, 62, 64, 72, 75, 77, 79, 80, 81, 82, 83, 85, 87, 89, 100, 104, or 109 relative to the VL as set forth in any one of SEQ ID NOs: 8, 16, and 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 1 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 2, SEQ ID NO: 731, or SEQ ID NO: 80 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 3 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 4 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 1 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 2, SEQ ID NO: 731, or SEQ ID NO: 80 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 3 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 4 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 145 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 147 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 148 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 149 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 145 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 147 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 148 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 149 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 6 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 150 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 152 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 153 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 154 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 150 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 152 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 7. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 153 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 5 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 154 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 8. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 9 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 10 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 11 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 12 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 9 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 10 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 11 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 12 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 155 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 156 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 157 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 158 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 159 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 155 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 156 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 157 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 158 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 159 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 14 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 160 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 161 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 162 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 163 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 164 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 160 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 161 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 162 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 15. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 163 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 13 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 164 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 16. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 18 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 19 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 20 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the IMGT definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 18 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 19 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 20 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the IMGT definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 166 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 167 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 168 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 169 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the Kabat definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 166 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 167 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 168 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 169 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 22 (according to the Kabat definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 170 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 171 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 172 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 173 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 174 (according to the Chothia definition system), and containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) in the framework regions as compared with the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 170 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 171 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 172 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VH as set forth in SEQ ID NO: 23. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 173 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 21 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 174 (according to the Chothia definition system), and is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical in the framework regions to the VL as set forth in SEQ ID NO: 24. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a chimeric antibody, which can include a heavy constant region and a light constant region from a human antibody. Chimeric antibodies refer to antibodies having a variable region or part of variable region from a first species and a constant region from a second species. Typically, in these chimeric antibodies, the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals (e.g., a non-human mammal such as mouse, rabbit, and rat), while the constant portions are homologous to the sequences in antibodies derived from another mammal such as human. In some embodiments, amino acid modifications can be made in the variable region and/or (e.g., and) the constant region. 
     In some embodiments, the anti-TfR antibody described herein is a chimeric antibody, which can include a heavy constant region and a light constant region from a human antibody. Chimeric antibodies refer to antibodies having a variable region or part of variable region from a first species and a constant region from a second species. Typically, in these chimeric antibodies, the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals (e.g., a non-human mammal such as mouse, rabbit, and rat), while the constant portions are homologous to the sequences in antibodies derived from another mammal such as human. In some embodiments, amino acid modifications can be made in the variable region and/or (e.g., and) the constant region. 
     In some embodiments, the heavy chain of any of the anti-TfR antibodies as described herein may comprises a heavy chain constant region (CH) or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof). The heavy chain constant region can of any suitable origin, e.g., human, mouse, rat, or rabbit. In one specific example, the heavy chain constant region is from a human IgG (a gamma heavy chain), e.g., IgG1, IgG2, or IgG4. An example of a human IgG1 constant region is given below: 
     
       
         
           
               
               
            
               
                   
                 (SEQ ID NO: 175) 
               
               
                   
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSW 
               
               
                   
               
               
                   
                 NSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYI 
               
               
                   
               
               
                   
                 CNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSV 
               
               
                   
               
               
                   
                 FLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDG 
               
               
                   
               
               
                   
                 VEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCK 
               
               
                   
               
               
                   
                 VSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQV 
               
               
                   
               
               
                   
                 SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSF 
               
               
                   
               
               
                   
                 FLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP 
               
               
                   
               
               
                   
                 GK 
               
            
           
         
       
     
     In some embodiments, the heavy chain of any of the anti-TfR antibodies described herein comprises a mutant human IgG1 constant region. For example, the introduction of LALA mutations (a mutant derived from mAb b12 that has been mutated to replace the lower hinge residues Leu234 Leu235 with Ala234 and Ala235) in the CH2 domain of human IgG1 is known to reduce Fcg receptor binding (Bruhns, P., et al. (2009) and Xu, D. et al. (2000)). The mutant human IgG1 constant region is provided below (mutations bonded and underlined): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 176) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALT 
               
               
                   
               
               
                 SGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKV 
               
               
                   
               
               
                 DKKVEPKSCDKTHTCPPCPAPE   AA   GGPSVFLFPPKPKDTLMISRTPE 
               
               
                   
               
               
                 VTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSV 
               
               
                   
               
               
                 LTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLP 
               
               
                   
               
               
                 PSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLD 
               
               
                   
               
               
                 SDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPG 
               
               
                   
               
               
                 K 
               
            
           
         
       
     
     In some embodiments, the light chain of any of the anti-TfR antibodies described herein may further comprise a light chain constant region (CL), which can be any CL known in the art. In some examples, the CL is a kappa light chain. In other examples, the CL is a lambda light chain. In some embodiments, the CL is a kappa light chain, the sequence of which is provided below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 177) 
               
               
                 RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNAL 
               
               
                   
               
               
                 QSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGL 
               
               
                   
               
               
                 SSPVTKSFNRGEC 
               
            
           
         
       
     
     Other antibody heavy and light chain constant regions are well known in the art, e.g., those provided in the IMGT database (www.imgt.org) or at www.vbase2.org/vbstat.php., both of which are incorporated by reference herein. 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 175 or SEQ ID NO: 176. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 175 or SEQ ID NO: 176. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region as set forth in SEQ ID NO: 175. In some embodiments, the anti-TfR antibody described herein comprises heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region as set forth in SEQ ID NO: 176. 
     In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising any one of the VL as listed in Table 2 or any variants thereof and a light chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 177. In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising any one of the VL as listed in Table 2 or any variants thereof and a light chain constant region contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 177. In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising any one of the VL as listed in Table 2 or any variants thereof and a light chain constant region set forth in SEQ ID NO: 177. 
     Examples of IgG heavy chain and light chain amino acid sequences of the anti-TfR antibodies described are provided in Table 5 below. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Heavy chain and light chain sequences of examples of anti-TfR IgGs 
               
            
           
           
               
               
            
               
                 Antibody 
                 IgG Heavy Chain/Light Chain Sequences 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                   
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPENGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPK 
               
               
                   
                 DTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLH 
               
               
                   
                 QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGF 
               
               
                   
                 YPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN 
               
               
                   
                 HYTQKSLSLSPGK (SEQ ID NO: 178) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                 Variant 1 
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPETGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPK 
               
               
                   
                 DTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLH 
               
               
                   
                 QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGF 
               
               
                   
                 YPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN 
               
               
                   
                 HYTQKSLSLSPGK (SEQ ID NO: 769) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                 Variant 2 
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPESGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPK 
               
               
                   
                 DTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLH 
               
               
                   
                 QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGF 
               
               
                   
                 YPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHN 
               
               
                   
                 HYTQKSLSLSPGK (SEQ ID NO: 770) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-M12 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                   
                 
                   DVQLQESGPGLVKPSQSLSLTCSVTGYSITSGYYWNWIRQFPGNKLEWMGYITFDGANNYNP 
                 
               
               
                   
                   SLKNRISITRDTSKNQFFLKLTSVTTEDTATYYCTRSSYDYDVLDYWGQGTTLTVSS ASTKG 
               
               
                   
                 PSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSS 
               
               
                   
                 VVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPK 
               
               
                   
                 PKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV 
               
               
                   
                 LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVK 
               
               
                   
                 GFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEAL 
               
               
                   
                 HNHYTQKSLSLSPGK (SEQ ID NO: 180) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIQMTQTTSSLSASLGDRVTISCRASQDISNFLNWYQQRPDGTVKLLIYYTSRLHSGVPSRF 
                 
               
               
                   
                   SGSGSGTDFSLTVSNLEQEDIATYFCQQGHTLPYTFGGGTKLEIK RTVAAPSVFIFPPSDEQ 
               
               
                   
                 LKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADY 
               
               
                   
                 EKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 181) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                   
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYCINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPP 
               
               
                   
                 KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLT 
               
               
                   
                 VLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLV 
               
               
                   
                 KGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEA 
               
               
                   
                 LHNHYTQKSLSLSPGK (SEQ ID NO: 182) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                 Variant 1 
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYYINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPP 
               
               
                   
                 KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLT 
               
               
                   
                 VLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLV 
               
               
                   
                 KGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEA 
               
               
                   
                 LHNHYTQKSLSLSPGK (SEQ ID NO: 771) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with wild type human IgG1 constant region) 
               
               
                 Variant 2 
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYDINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPP 
               
               
                   
                 KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLT 
               
               
                   
                 VLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLV 
               
               
                   
                 KGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEA 
               
               
                   
                 LHNHYTQKSLSLSPGK (SEQ ID NO: 772) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 * VH/VL sequences underlined 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 178, SEQ ID NO: 180, SEQ ID NO: 182, SEQ ID NO: 769, SEQ ID NO: 770, SEQ ID NO: 771, or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 178, SEQ ID NO: 180, SEQ ID NO: 182, SEQ ID NO: 769, SEQ ID NO: 770, SEQ ID NO: 771, or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 178, SEQ ID NO: 180, SEQ ID NO: 182, SEQ ID NO: 769, SEQ ID NO: 770, SEQ ID NO: 771, or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 178, SEQ ID NO: 769, or SEQ ID NO: 770. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 10, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 179. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 178, SEQ ID NO: 769, or SEQ ID NO: 770. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 179. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 178, SEQ ID NO: 769, or SEQ ID NO: 770. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 179. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 180. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 181. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 180. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 181. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 180. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 181. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 182, SEQ ID NO: 771 or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 182, SEQ ID NO: 771 or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 182, SEQ ID NO: 771 or SEQ ID NO: 772. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 183. 
     In some embodiments, the anti-TfR antibody is a FAB fragment, F(ab′) fragment, or F(ab′) 2  fragment of an intact antibody (full-length antibody). Antigen binding fragment of an intact antibody (full-length antibody) can be prepared via routine methods (e.g., recombinantly or by digesting the heavy chain constant region of a full length IgG using an enzyme such as papain). For example, F(ab′) 2  fragments can be produced by pepsin or papain digestion of an antibody molecule, and Fab fragments that can be generated by reducing the disulfide bridges of F(ab′) 2  fragments. In some embodiments, a heavy chain constant region in a F(ab′) fragment of the anti-TfR1 antibody described herein comprises the amino acid sequence of: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 184) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTS 
               
               
                   
               
               
                 GVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK 
               
               
                   
               
               
                 KVEPKSCDKTHT 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 184. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 184. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising any one of the VH as listed in Table 2 or any variants thereof and a heavy chain constant region as set forth in SEQ ID NO: 184. 
     Examples of F(ab′) amino acid sequences of the anti-TfR antibodies described herein are provided in Table 6. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Heavy chain and light chain sequences of examples of anti-TfR F(ab′) 
               
            
           
           
               
               
            
               
                 Antibody 
                 F(ab′) Heavy Chain/Light Chain Sequences 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                   
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPENGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 185) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                 Variant 1 
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPETGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 773) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-A4 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                 Variant 2 
                 
                   EVQLQQSGAELVRPGASVKLSCTASGFNIKDDYMYWVKQRPEQGLEWIGWIDPESGDTEYAS 
                 
               
               
                   
                   KFQDKATVTADTSSNTAYLQLSSLTSEDTAVYYCTLWLRRGLDYWGQGTSVTVSS ASTKGPS 
               
               
                   
                 VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVV 
               
               
                   
                 TVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 774) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVMTQAAPSVPVTPGESVSISCRSSKSLLHSNGYTYLFWFLQRPGQSPQLLIYRMSNLASG 
                 
               
               
                   
                   VPDRFSGSGSGTAFTLRISRVEAEDVGVYYCMQHLEYPFTFGGGTKLEIK RTVAAPSVFIFP 
               
               
                   
                 PSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTL 
               
               
                   
                 SKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 179) 
               
               
                   
               
               
                 3-M12 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                   
                 
                   DVQLQESGPGLVKPSQSLSLTCSVTGYSITSGYYWNWIRQFPGNKLEWMGYITFDGANNYNP 
                 
               
               
                   
                   SLKNRISITRDTSKNQFFLKLTSVTTEDTATYYCTRSSYDYDVLDYWGQGTTLTVSS ASTKG 
               
               
                   
                 PSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSS 
               
               
                   
                 VVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 186) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIQMTQTTSSLSASLGDRVTISCRASQDISNFLNWYQQRPDGTVKLLIYYTSRLHSGVPSRF 
                 
               
               
                   
                   SGSGSGTDFSLTVSNLEQEDIATYFCQQGHTLPYTFGGGTKLEIK RTVAAPSVFIFPPSDEQ 
               
               
                   
                 LKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADY 
               
               
                   
                 EKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 181) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                   
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYCINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 187) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                 Variant 1 
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYYINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 775) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 5-H12 
                 Heavy Chain (with partial human IgG1 constant region) 
               
               
                 Variant 2 
                 
                   QIQLQQSGPELVRPGASVKISCKASGYSFTDYDINWVNQRPGQGLEWIGWIYPGSGNTRYSE 
                 
               
               
                   
                   RFKGKATLTVDTSSNTAYMQLSSLTSEDSAVYFCAREDYYPYHGMDYWGQGTSVTVSS ASTK 
               
               
                   
                 GPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLS 
               
               
                   
                 SVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 776) 
               
               
                   
                 Light Chain (with kappa light chain constant region) 
               
               
                   
                 
                   DIVLTQSPTSLAVSLGQRATISCRASESVDGYDNSFMHWYQQKPGQPPKLLIFRASNLESGI 
                 
               
               
                   
                   PARFSGSGSRTDFTLTINPVEAADVATYYCQQSSEDPWTFGGGTKLEIK RTVAAPSVFIFPP 
               
               
                   
                 SDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLS 
               
               
                   
                 KADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 183) 
               
               
                   
               
               
                 * VH/VL sequences underlined 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 185, SEQ ID NO: 186, SEQ ID NO: 187, SEQ ID NO: 773, SEQ ID NO: 774. SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 185, SEQ ID NO: 186, SEQ ID NO: 187, SEQ ID NO: 773, SEQ ID NO: 774. SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 185, SEQ ID NO: 186, SEQ ID NO: 187, SEQ ID NO: 773, SEQ ID NO: 774. SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 179, SEQ ID NO: 181, or SEQ ID NO: 183. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 185, SEQ ID NO: 773, or SEQ ID NO: 774. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 179. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 185, SEQ ID NO: 773, or SEQ ID NO: 774. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 179. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 185, SEQ ID NO: 773, or SEQ ID NO: 774. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 179. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 186. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 10, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 181. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 186. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 181. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 186. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 181. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 187, SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 187, SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 183. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 187, SEQ ID NO: 775, or SEQ ID NO: 776. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 183. 
     The anti-TfR receptor antibodies described herein can be in any antibody form, including, but not limited to, intact (i.e., full-length) antibodies, antigen-binding fragments thereof (such as Fab, F(ab′), F(ab′)2, Fv), single chain antibodies, bi-specific antibodies, or nanobodies. In some embodiments, the anti-TfR antibody described herein is a scFv. In some embodiments, the anti-TfR antibody described herein is a scFv-Fab (e.g., scFv fused to a portion of a constant region). In some embodiments, the anti-TfR receptor antibody described herein is a scFv fused to a constant region (e.g., human IgG1 constant region as set forth in SEQ ID NO: 175 or SEQ ID NO: 176, or a portion thereof such as the Fc portion) at either the N-terminus of C-terminus. 
     In some embodiments, any one of the anti-TfR1 antibodies described herein may comprise a signal peptide in the heavy and/or (e.g., and) light chain sequence (e.g., a N-terminal signal peptide). In some embodiments, the anti-TfR1 antibody described herein comprises any one of the VH and VL sequences, any one of the IgG heavy chain and light chain sequences, or any one of the F(ab′) heavy chain and light chain sequences described herein, and further comprises a signal peptide (e.g., a N-terminal signal peptide). In some embodiments, the signal peptide comprises the amino acid sequence of MGWSCIILFLVATATGVHS (SEQ ID NO: 214). 
     The present disclosure, in some aspects, provide another new anti-TfR antibody that can be used as a muscle-targeting agent (e.g., in a muscle-targeting complex). The CDR sequences and variable domain sequences of the antibody are provided in Table 7. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 CDR sequences of an anti-TfR antibody 
               
               
                 according to different definition systems 
               
               
                 and variable domain sequences 
               
            
           
           
               
               
               
               
            
               
                 No. 
                   
                   
                   
               
               
                 system 
                 IMGT 
                 Kabat 
                 Chothia 
               
               
                   
               
               
                 CDR-H1 
                 GYSFTSYW 
                 SYWIG 
                 GYSFTSY 
               
               
                   
                 (SEQ ID NO: 188) 
                 (SEQ ID NO: 194) 
                 (SEQ ID NO: 199) 
               
               
                   
               
               
                 CDR-H2 
                 IYPGDSDT 
                 IIYPGDSDTRYSPSFQGQ 
                 GDS 
               
               
                   
                 (SEQ ID NO: 189) 
                 (SEQ ID NO: 195) 
                 (SEQ ID NO: 200) 
               
               
                   
               
               
                 CDR-H3 
                 ARFPYDSSGYYSFDY 
                 FPYDSSGYYSFDY 
                 PYDSSGYYSFD 
               
               
                   
                 (SEQ ID NO: 190) 
                 (SEQ ID NO: 196) 
                 (SEQ ID NO: 201) 
               
               
                   
               
               
                 CDR-L1 
                 QSISSY 
                 RASQSISSYLN 
                 SQSISSY 
               
               
                   
                 (SEQ ID NO: 191) 
                 (SEQ ID NO: 197) 
                 (SEQ ID NO: 202) 
               
               
                   
               
               
                 CDR-L2 
                 AAS 
                 AASSLQS 
                 AAS  
               
               
                   
                 (SEQ ID NO: 192) 
                 (SEQ ID NO: 198) 
                 (SEQ ID NO: 192) 
               
               
                   
               
               
                 CDR-L3 
                 QQSYSTPLT 
                 QQSYSTPLT 
                 SYSTPL  
               
               
                   
                 (SEQ ID NO: 193) 
                 (SEQ ID NO: 193) 
                 (SEQ ID NO: 203) 
               
               
                   
               
            
           
           
               
               
            
               
                 VH 
                 QVQLVQSGAEVKKPGESLKISCKGS GYSFTSYW IGWVRQMPGKGLEWMGI IYPGDSDT RY 
               
               
                   
                 SPSFQGQVTISADKSISTAYLQWSSLKASDTAMYYC ARFPYDSSGYYSFDY WGQGTLVTV 
               
               
                   
                 SS (SEQ ID NO: 204) 
               
               
                   
               
               
                 VL 
                 DIQMTQSPSSLSASVGDRVTITCRAS QSISSY LNWYQQKPGKAPKLLIY AAS SLQSGVPS 
               
               
                   
                 RFSGSGSGTDFTLTISSLQPEDFATYYC QQSYSTPLT FGGGTKVEIK  
               
               
                   
                 (SEQ ID NO: 205) 
               
               
                   
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibodies of the present disclosure comprises one or more of the CDR-H (e.g., CDR-H1, CDR-H2, and CDR-H3) amino acid sequences from any one of the anti-TfR antibodies selected from Table 7. In some embodiments, the anti-TfR antibodies of the present disclosure comprise the CDR-H1, CDR-H2, and CDR-H3 as provided for each numbering system provided in Table 7. In some embodiments, the anti-TfR antibodies of the present disclosure comprises one or more of the CDR-L (e.g., CDR-L1, CDR-L2, and CDR-L3) amino acid sequences from any one of the anti-TfR antibodies selected from Table 7. In some embodiments, the anti-TfR antibodies of the present disclosure comprise the CDR-L1, CDR-L2, and CDR-L3 as provided for teach numbering system provided in Table 7. 
     In some embodiments, the anti-TfR antibodies of the present disclosure comprises the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 as provided for each numbering system provided in Table 7. In some embodiments, antibody heavy and light chain CDR3 domains may play a particularly important role in the binding specificity/affinity of an antibody for an antigen. Accordingly, the anti-TfR antibodies of the disclosure may include at least the heavy and/or (e.g., and) light chain CDR3s of any one of the anti-TfR antibody provided in Table 7. 
     In some examples, any of the anti-TfR antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any of the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and/or (e.g., and) CDR-L3 sequences provided in Table 7. In some embodiments, the position of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary by one, two, three, four, five, or six amino acid positions so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). For example, in some embodiments, the position defining a CDR of any antibody described herein can vary by shifting the N-terminal and/or (e.g., and) C-terminal boundary of the CDR by one, two, three, four, five, or six amino acids, relative to the CDR position of any one of the antibodies described herein, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). In another embodiment, the length of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary (e.g., be shorter or longer) by one, two, three, four, five, or more amino acids, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). 
     Accordingly, in some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids shorter than one or more of the CDRs described herein (e.g., provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids longer than one or more of the CDRs described herein (e.g., CDRS from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRs from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). Any method can be used to ascertain whether immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained, for example, using binding assays and conditions described in the art. 
     In some examples, any of the anti-TfR antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any one of the anti-TfR antibody provided in Table 7. For example, the antibodies may include one or more CDR sequence(s) from the anti-TfR antibody provided in Table 7 and containing up to 5, 4, 3, 2, or 1 amino acid residue variations as compared to the corresponding CDR region in any one of the CDRs provided herein (e.g., CDRs from the anti-TfR antibody provided in Table 7) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, any of the amino acid variations in any of the CDRs provided herein may be conservative variations. Conservative variations can be introduced into the CDRs at positions where the residues are not likely to be involved in interacting with a transferrin receptor protein (e.g., a human transferrin receptor protein), for example, as determined based on a crystal structure. 
     Some aspects of the disclosure provide anti-TfR antibodies that comprise one or more of the heavy chain variable (VH) and/or (e.g., and) light chain variable (VL) domains provided herein. In some embodiments, the anti-TfR antibodies of the disclosure include any antibody that includes a heavy chain variable domain and/or (e.g., and) a light chain variable domain of the anti-TfR1 antibody provided in Table 7. 
     Aspects of the disclosure provide anti-TfR antibodies having a heavy chain variable (VH) and/or (e.g., and) a light chain variable (VL) domain amino acid sequence homologous to any of those described herein. In some embodiments, the anti-TfR antibody comprises a heavy chain variable sequence or a light chain variable sequence that is at least 75% (e.g., 80%, 85%, 90%, 95%, 98%, or 99%) identical to the heavy chain variable sequence and/or any light chain variable sequence provided in Table 7. In some embodiments, the homologous heavy chain variable and/or (e.g., and) a light chain variable amino acid sequences do not vary within any of the CDR sequences provided herein. For example, in some embodiments, the degree of sequence variation (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) may occur within a heavy chain variable and/or (e.g., and) a light chain variable sequence excluding any of the CDR sequences provided herein. In some embodiments, any of the anti-TfR antibodies provided herein comprise a heavy chain variable sequence and a light chain variable sequence that comprises a framework sequence that is at least 75%, 80%, 85%, 90%, 95%, 98%, or 99% identical to the framework sequence of any anti-TfR antibody provided in Table 7. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 of a heavy chain variable domain having the amino acid sequence of SEQ ID NO: 204. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 of a light chain variable domain having the amino acid sequence of SEQ ID NO: 205. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 188 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 189 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 190 (according to the IMGT definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 191 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the IMGT definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 188, CDR-H2 having the amino acid sequence of SEQ ID NO: 189, and CDR-H3 having the amino acid sequence of SEQ ID NO: 190. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 191, CDR-L2 having the amino acid sequence of SEQ ID NO: 192, and CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 188, CDR-H2 having the amino acid sequence of SEQ ID NO: 189, and CDR-H3 having the amino acid sequence of SEQ ID NO: 190. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 191, CDR-L2 having the amino acid sequence of SEQ ID NO: 192, and CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 188; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 189; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 190. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 191; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 192; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 194 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 195 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 196 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 197 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 198 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the Kabat definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 194, CDR-H2 having the amino acid sequence of SEQ ID NO: 195, and CDR-H3 having the amino acid sequence of SEQ ID NO: 196. “Collectively” means that the total number of amino acid variations in all of the three heavy chain CDRs is within the defined range. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 197, CDR-L2 having the amino acid sequence of SEQ ID NO: 198, and CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 194, CDR-H2 having the amino acid sequence of SEQ ID NO: 195, and CDR-H3 having the amino acid sequence of SEQ ID NO: 196. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 197, CDR-L2 having the amino acid sequence of SEQ ID NO: 198, and CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 194; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 195; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 196. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 197; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 198; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 199 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 200 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 201 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 202 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 203 (according to the Chothia definition system). 
     In some embodiments, anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 199, CDR-H2 having the amino acid sequence of SEQ ID NO: 200, and CDR-H3 having the amino acid sequence of SEQ ID NO: 201. “Collectively” means that the total number of amino acid variations in all of the three heavy chain CDRs is within the defined range. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 202, CDR-L2 having the amino acid sequence of SEQ ID NO: 192, and CDR-L3 having the amino acid sequence of SEQ ID NO: 203. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the CDR-H1 having the amino acid sequence of SEQ ID NO: 199, CDR-H2 having the amino acid sequence of SEQ ID NO: 200, and CDR-H3 having the amino acid sequence of SEQ ID NO: 201. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that collectively are at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the to the CDR-L1 having the amino acid sequence of SEQ ID NO: 202, CDR-L2 having the amino acid sequence of SEQ ID NO: 192, and CDR-L3 having the amino acid sequence of SEQ ID NO: 203. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises: a CDR-H1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H1 having the amino acid sequence of SEQ ID NO: 199; a CDR-H2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H2 having the amino acid sequence of SEQ ID NO: 200; and/or (e.g., and) a CDR-H3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-H3 having the amino acid sequence of SEQ ID NO: 201. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises: a CDR-L1 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L1 having the amino acid sequence of SEQ ID NO: 202; a CDR-L2 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L2 having the amino acid sequence of SEQ ID NO: 192; and/or (e.g., and) a CDR-L3 having no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 having the amino acid sequence of SEQ ID NO: 203. 
     In some embodiments, the In some embodiments, the anti-TfR antibody of the present disclosure comprises a CDR-H1 comprising the amino acid sequence of SEQ ID NO: 194, a CDR-H2 comprising the amino acid sequence of SEQ ID NO: 189, a CDR-H3 comprising the amino acid sequence of SEQ ID NO: 196, a CDR-L1 comprising the amino acid sequence of SEQ ID NO: 197, a CDR-L2 comprising the amino acid sequence of SEQ ID NO: 198, and a CDR-L3 comprising the amino acid sequence of SEQ ID NO: 193. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a human antibody comprising a VH comprising the amino acid sequence of SEQ ID NO: 204. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure is a human antibody comprising a VL comprising the amino acid sequence of SEQ ID NO: 205. In some embodiments, the present disclosure contemplate other humanized/human antibodies comprising the CDR-H1, CDR-H1, CDR-H3 of the VH comprising SEQ ID NO: 204 and the CDR-L1, CDR-L1, and CDR-L3 of the VL comprising SEQ ID NO: 205 with human framework regions. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 204. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 204. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody. In some embodiments, the humanized anti-TfR antibody comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 188 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 189 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 190 (according to the IMGT definition system); and a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 191 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the IMGT definition system), wherein the humanized VH comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 204, and the humanized VL comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the humanized anti-TfR antibody comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 188 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 189 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 190 (according to the IMGT definition system); and a humanized VL comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 191 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the IMGT definition system), wherein the humanized VH contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 204, and the humanized VL contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the humanized anti-TfR antibody comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 194 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 195 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 196 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 197 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 198 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the Kabat definition system), wherein the humanized VH comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 204, and the humanized VL comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the humanized anti-TfR antibody comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 194 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 195 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 196 (according to the Kabat definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 197 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 198 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the Kabat definition system), wherein the humanized VH contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 204, and the humanized VL contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the humanized anti-TfR antibody comprises a humanized VH comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 199 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 200 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 201 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 202 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 203 (according to the Chothia definition system), wherein the humanized VH comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 204, and the humanized VL comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the humanized anti-TfR antibody comprises a CDR-H1 having the amino acid sequence of SEQ ID NO: 199 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 200 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 201 (according to the Chothia definition system), a CDR-L1 having the amino acid sequence of SEQ ID NO: 202 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 203 (according to the Chothia definition system), wherein the humanized VH contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 204, and the humanized VL contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 205. 
     In some embodiments, the anti-TfR antibody is an IgG, a Fab fragment, a F(ab′) 2  fragment, a scFv, or an scFv fused to a constant region (e.g., N- or C-terminal fusion). Non-limiting examples of anti-TfR antibodies in different formats are provided herein. 
     In some embodiments, the anti-TfR1 antibody is a single-chain fragment variable (scFv) comprising the VH and VL in a single polypeptide chain. In some embodiments, the scFv comprises any one of the heavy chain CDRs, light chain CDRs, VHs, and/or (e.g., and) VLs described herein on a single polypeptide chain. In some embodiments, the scFv comprises the VH linked at the N-terminus of the VL. In some embodiments, the scFv comprises the VL linked at the N-terminus of the VH. In some embodiments, the VH and VL are linked via a linker (e.g., a polypeptide linker). Any polypeptide linker can be used for linking the VH and VL in the scFv. Selection of a linker sequence is within the abilities of those skilled in the art. 
     In some embodiments, the scFv comprises a VH (e.g., a humanized VH) comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 188 (according to the IMGT definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 189 (according to the IMGT definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 190 (according to the IMGT definition system); and a VL (e.g., a humanized VL) comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 191 (according to the IMGT definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the IMGT definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the IMGT definition system), wherein the VH and VL are on a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFv comprises a VH (e.g., a humanized VH) comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 194 (according to the Kabat definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 195 (according to the Kabat definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 196 (according to the Kabat definition system); and a VL (e.g., a humanized VL) comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 197 (according to the Kabat definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 198 (according to the Kabat definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 193 (according to the Kabat definition system), wherein the VH and VL are on a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFv comprises a VH (e.g., a humanized VH) comprising a CDR-H1 having the amino acid sequence of SEQ ID NO: 199 (according to the Chothia definition system), a CDR-H2 having the amino acid sequence of SEQ ID NO: 200 (according to the Chothia definition system), a CDR-H3 having the amino acid sequence of SEQ ID NO: 201 (according to the Chothia definition system); and a VL (e.g., a humanized VL) comprising a CDR-L1 having the amino acid sequence of SEQ ID NO: 202 (according to the Chothia definition system), a CDR-L2 having the amino acid sequence of SEQ ID NO: 192 (according to the Chothia definition system), and a CDR-L3 having the amino acid sequence of SEQ ID NO: 203 (according to the Chothia definition system), wherein the VH and VL are on a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFV comprises a VH (e.g., a humanized VH) comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 204 and a VL (e.g., a humanized VL) comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VL as set forth in SEQ ID NO: 205, wherein the VH and VL are in a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFV comprises a VH (e.g., a humanized VH) that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 204, and a humanized VL (e.g., a humanized VL) that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 205, wherein the VH and VL are in a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFV comprises a VH comprising the amino acid sequence of SEQ ID NO: 204 and a VL comprising the amino acid sequence of SEQ ID NO: 205, wherein the VH and VL are in a single polypeptide chain (e.g., linked via an amide bond or linked via a linker such as a peptide linker), and wherein the VH is linked to the N-terminus or the C-terminus of the VL. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFv comprises a VH comprising the amino acid sequence of SEQ ID NO: 204 linked to the N-terminus of a VL comprising the amino acid sequence of SEQ ID NO: 205. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     In some embodiments, the scFv comprises a VH comprising the amino acid sequence of SEQ ID NO: 204 linked to the C-terminus of a VL comprising the amino acid sequence of SEQ ID NO: 205. In some embodiments, the VH and VL are linked via a linker comprising the amino acid sequence of EGKSSGSGSESKAS (SEQ ID NO: 215). 
     The amino acid sequence of an scFV is provided below (VL-linker-VH): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 206) 
               
               
                 
                   DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYA 
                 
               
               
                   
               
               
                 
                   ASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGG 
                 
               
               
                   
               
               
                 
                   GTKVEIK 
                   EGKSSGSGSESKAS 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSF 
                 
               
               
                   
               
               
                 
                   TSYWIGWVRQMPGKGLEWMGIIYPGDSDTRYSPSFQGQVTISADKSISTA 
                 
               
               
                   
               
               
                 
                   YLQWSSLKASDTAMYYCARFPYDSSGYYSFDYWGQGTLVTVSS 
                 
               
            
           
         
       
     
     In some embodiments, the scFv described herein comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the VH as set forth in SEQ ID NO: 206. In some embodiments, the scFv described herein comprises an amino acid sequence that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 206. In some embodiments, the scFv comprises the amino acid sequence of SEQ ID NO: 206. 
     In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein) linked to a constant region. In some embodiments, the Fc region is a fragment crystallizable region (Fc region). The Fc region is a fragment of a heavy chain constant region that interacts with cell surface receptors called Fc receptors. Any known Fc regions may be used in accordance with the present disclosure and be fused to any one of the scFv described herein. The amino acid sequence of an example of Fc region is provided below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 207) 
               
               
                 PKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV 
               
               
                   
               
               
                 SHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNG 
               
               
                   
               
               
                 KEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLT 
               
               
                   
               
               
                 CLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR 
               
               
                   
               
               
                 WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein or variants thereof) linked (e.g., via an amide bond or a linker such as a peptide linker) at the C-terminus to a Fc region that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the Fc region as set forth in SEQ ID NO: 207. In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein or variants thereof) linked (e.g., via an amide bond or a linker such as a peptide linker) at the C-terminus to a Fc region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 207. In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein or variants thereof) linked (e.g., via an amide bond or a linker such as a peptide linker) at the C-terminus to a Fc region set forth in SEQ ID NO: 207. In some embodiments, the scFV and the Fc are linked via a linker comprising the amino acid sequence of DIEGRMD (SEQ ID NO: 729). 
     The amino acid sequence of an example of anti-TfR antibody comprising an scFv (e.g., any one of the scFv described herein) linked at the C-terminus to a Fc region is provided below (VL-linker1-VH-linker2-Fc): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 208) 
               
               
                 
                   DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYA 
                 
               
               
                   
               
               
                 
                   ASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGG 
                 
               
               
                   
               
               
                 
                   GTKVEIK 
                   EGKSSGSGSESKAS 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSF 
                 
               
               
                   
               
               
                 
                   TSYWIGWVRQMPGKGLEWMGIIYPGDSDTRYSPSFQGQVTISADKSISTA 
                 
               
               
                   
               
               
                 
                   YLQWSSLKASDTAMYYCARFPYDSSGYYSFDYWGQGTLVTVSS 
                   DIEGRMD 
                 
               
               
                   
               
               
                 
                   PKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV 
                 
               
               
                   
               
               
                 
                   SHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNG 
                 
               
               
                   
               
               
                 
                   KEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLT 
                 
               
               
                   
               
               
                 
                   CLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR 
                 
               
               
                   
               
               
                 
                   WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 
                 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 208. In some embodiments, the anti-TfR antibody described herein comprises an amino acid sequence that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 208. In some embodiments, the anti-TfR antibody comprises the amino acid sequence of SEQ ID NO: 208. 
     In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein) linked (e.g., via an amide bond or a linker such as a peptide linker) at the N-terminus to a Fc region that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the Fc region as set forth in SEQ ID NO: 207. In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein) linked (e.g., via an amide bond or a linker such as a peptide linker) at the N-terminus to a Fc region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 207. In some embodiments, the anti-TfR antibody described herein comprises an scFv (e.g., any one of the scFv described herein) linked (e.g., via an amide bond or a linker such as a peptide linker) at the N-terminus to a Fc region set forth in SEQ ID NO: 207. In some embodiments, the scFV and the Fc are linked via a linker comprising the amino acid sequence of DIEGRMD (SEQ ID NO: 729). 
     The amino acid sequence of an example of anti-TfR antibody comprising an scFv (e.g., any one of the scFv described herein) linked at the N-terminus to a Fc region is provided below (Fc-linker2-VL-linker1-VH): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 209) 
               
               
                 
                   PKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV 
                 
               
               
                   
               
               
                 
                   SHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNG 
                 
               
               
                   
               
               
                 
                   KEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLT 
                 
               
               
                   
               
               
                 
                   CLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR 
                 
               
               
                   
               
               
                 
                   WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 
                   DIEGRMD 
                   DIQMTQSPSSLS 
                 
               
               
                   
               
               
                 
                   ASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYAASSLQSGVPSRF 
                 
               
               
                   
               
               
                 
                   SGSGSGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGGGTKVEIK 
                   EGKSS 
                 
               
               
                   
               
               
                 
                   GSGSESKAS 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSFTSYWIGWVRQMP 
                 
               
               
                   
               
               
                 
                   GKGLEWMGIIYPGDSDTRYSPSFQGQVTISADKSISTAYLQWSSLKASDT  
                 
               
               
                   
               
               
                 
                   AMYYCARFPYDSSGYYSFDYWGQGTLVTVSS 
                 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 209. In some embodiments, the anti-TfR antibody described herein comprises an amino acid sequence that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with SEQ ID NO: 209. In some embodiments, the anti-TfR antibody comprises the amino acid sequence of SEQ ID NO: 209. 
     In some embodiments, the anti-TfR antibody described herein is an IgG. In some embodiments, the IgG comprises a heavy chain and a light chain, wherein the heavy chain comprises the CDR-H1, CDRH2, and CDR-H3 of any one of the anti-TfR antibodies described herein, and further comprises a heavy chain constant region or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof); and wherein the light chain comprises the CDR-L1, CDRL2, and CDR-L3 of any one of the anti-TfR antibodies described herein, and further comprises a light chain constant region. In some embodiments, the IgG comprises a heavy chain and a light chain, wherein the heavy chain comprises the VH of any one of the anti-TfR antibodies described herein, and further comprises a heavy chain constant region or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof); and wherein the light chain comprises the VL of any one of the anti-TfR antibodies described herein, and further comprises a light chain constant region. 
     The heavy chain constant region can of any suitable origin, e.g., human, mouse, rat, or rabbit. In one specific example, the heavy chain constant region is from a human IgG (a gamma heavy chain), e.g., IgG1, IgG2, or IgG4. An example of human IgG1 constant region is given below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 175) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGV 
               
               
                   
               
               
                 HTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP 
               
               
                   
               
               
                 KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS 
               
               
                   
               
               
                 HEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGK 
               
               
                   
               
               
                 EYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTC 
               
               
                   
               
               
                 LVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW 
               
               
                   
               
               
                 QQGNVFSCSVMHEALHNHYTQKSLSLSPGK 
               
            
           
         
       
     
     In some embodiments, the heavy chain of any of the anti-TfR antibodies described herein comprises a mutant human IgG1 constant region. For example, the introduction of LALA mutations (a mutant derived from mAb b12 that has been mutated to replace the lower hinge residues Leu234 Leu235 with Ala234 and Ala235) in the CH2 domain of human IgG1 is known to reduce Fcg receptor binding (Bruhns, P., et al. (2009) and Xu, D. et al. (2000)). The mutant human IgG1 constant region is provided below (mutations bonded and underlined): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 176) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGV 
               
               
                   
               
               
                 HTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP 
               
               
                   
               
               
                 KSCDKTHTCPPCPAPE   AA   GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS 
               
               
                   
               
               
                 HEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGK 
               
               
                   
               
               
                 EYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTC 
               
               
                   
               
               
                 LVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW 
               
               
                   
               
               
                 QQGNVFSCSVMHEALHNHYTQKSLSLSPGK 
               
            
           
         
       
     
     In some embodiments, the light chain constant region of any of the anti-TfR antibodies described herein can be any light chain constant region known in the art. In some examples, a kappa light chain or a lambda light chain. In some embodiments, the light chain constant region is a kappa light chain, the sequence of which is provided below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 177) 
               
               
                 RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSG 
               
               
                   
               
               
                 NSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTK 
               
               
                   
               
               
                 SFNRGEC 
               
            
           
         
       
     
     Other antibody heavy and light chain constant regions are well known in the art, e.g., those provided in the IMGT database (www.imgt.org) or at www.vbase2.org/vbstat.php., both of which are incorporated by reference herein. 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the a VH comprising the amino acid sequence of SEQ ID NO: 204 or any variants thereof and a heavy chain constant region that at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 175 or SEQ ID NO: 176. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the a VH comprising the amino acid sequence of SEQ ID NO: 204 or any variants thereof and a heavy chain constant region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 175 or SEQ ID NO: 176. 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising a VH set forth in SEQ ID NO: 204 and a heavy chain constant region set forth in SEQ ID NO: 175. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising a VH set forth in SEQ ID NO: 204 and a heavy chain constant region as set forth in SEQ ID NO: 176. 
     In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising a VL comprising the amino acid sequence of SEQ ID NO: 205 or any variants thereof and a light chain constant region that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 177. In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising a VL comprising the amino acid sequence of SEQ ID NO: 205 or any variants thereof and a light constant region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 177. 
     In some embodiments, the anti-TfR antibody described herein comprises a light chain comprising a VL set forth in SEQ ID NO: 205 and a light chain constant region as set forth in SEQ ID NO: 177. 
     Examples of IgG heavy chain and light chain amino acid sequences of the anti-TfR antibodies described are provided below. 
     
       
         
           
               
            
               
                 anti-TfR IgG heavy chain (with wild type human  
               
               
                 IgG1 constant region, VH underlined) 
               
               
                 (SEQ ID NO: 210) 
               
               
                 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSFTSYWIGWVRQMPGKGLEWMGI 
                 
               
               
                   
               
               
                 
                   IYPGDSDTRYSPSFQGQVTISADKSISTAYLQWSSLKASDTAMYYCARFP 
                 
               
               
                   
               
               
                   YDSSGYYSFDYWGQGTLVTVSS ASTKGPSVFPLAPSSKSTSGGTAALGCL 
               
               
                   
               
               
                 VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT 
               
               
                   
               
               
                 QTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLLGGPSVFLFP 
               
               
                   
               
               
                 PKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREE 
               
               
                   
               
               
                 QYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPR 
               
               
                   
               
               
                 EPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTT 
               
               
                   
               
               
                 PPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLS 
               
               
                   
               
               
                 PGK 
               
               
                   
               
               
                 anti-TfR IgG heavy chain (with human IgG1 constant 
               
               
                 region mutant L234A/L235A, VH underlined) 
               
               
                 (SEQ ID NO: 211) 
               
               
                 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSFTSYWIGWVRQMPGKGLEWMGI 
                 
               
               
                   
               
               
                 
                   IYPGDSDTRYSPSFQGQVTISADKSISTAYLQWSSLKASDTAMYYCARFP 
                 
               
               
                   
               
               
                   YDSSGYYSFDYWGQGTLVTVSS ASTKGPSVFPLAPSSKSTSGGTAALGCL 
               
               
                   
               
               
                 VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT 
               
               
                   
               
               
                 QTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPEAAGGPSVFLFPP 
               
               
                   
               
               
                 KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQ 
               
               
                   
               
               
                 YNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPRE 
               
               
                   
               
               
                 PQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP 
               
               
                   
               
               
                 PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP 
               
               
                   
               
               
                 GK 
               
               
                   
               
               
                 anti-TfR IgG light chain (kappa, VL underlined) 
               
               
                 (SEQ ID NO: 212) 
               
               
                 
                   DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYA 
                 
               
               
                   
               
               
                 
                   ASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGG 
                 
               
               
                   
               
               
                   GTKVEIK RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKV 
               
               
                   
               
               
                 DNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQG 
               
               
                   
               
               
                 LSSPVTKSFNRGEC  
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 210 or SEQ ID NO: 211. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 212. 
     In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 210 or SEQ ID NO: 211. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 212. 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 210 or SEQ ID NO: 211. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of any one of SEQ ID NO: 212. 
     In some embodiments, the anti-TfR antibody is a FAB fragment or F(ab′) 2  fragment of an intact antibody (full-length antibody). Antigen binding fragment of an intact antibody (full-length antibody) can be prepared via routine methods (e.g., recombinantly or by digesting the heavy chain constant region of a full length IgG using an enzyme such as papain). For example, F(ab′) 2  fragments can be produced by pepsin or papain digestion of an antibody molecule, and Fab fragments that can be generated by reducing the disulfide bridges of F(ab′) 2  fragments. In some embodiments, a heavy chain constant region in a F(ab′) fragment of the anti-TfR1 antibody described herein comprises the amino acid sequence of: ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVT VPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 184) 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the a VH comprising the amino acid sequence of SEQ ID NO: 204 or any variants thereof and a heavy chain constant region that at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 184. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the a VH comprising the amino acid sequence of SEQ ID NO: 204 or any variants thereof and a heavy chain constant region that contains no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 184. 
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising a VH set forth in SEQ ID NO: 204 and a heavy chain constant region as set forth in SEQ ID NO: 184. 
     Exemplary F(ab′) amino acid sequences of an anti-TfR antibody described herein are provided below. 
     
       
         
           
               
            
               
                 anti-TfR Fab′ heavy chain (with human IgG1 
               
               
                 constant region fragment, VH underlined) 
               
               
                 (SEQ ID NO: 213) 
               
               
                 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSFTSYWIGWVRQMPGKGLEWMGI 
                 
               
               
                   
               
               
                 
                   IYPGDSDTRYSPSFQGQVTISADKSISTAYLQWSSLKASDTAMYYCARFP 
                 
               
               
                   
               
               
                   YDSSGYYSFDYWGQGTLVTVSS ASTKGPSVFPLAPSSKSTSGGTAALGCL 
               
               
                   
               
               
                 VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT 
               
               
                   
               
               
                 QTYICNVNHKPSNTKVDKKVEPKSCDKTHTCP 
               
               
                 or 
               
               
                   
               
               
                 (SEQ ID NO: 777) 
               
               
                 
                   QVQLVQSGAEVKKPGESLKISCKGSGYSFTSYWIGWVRQMPGKGLEWMGI 
                 
               
               
                   
               
               
                 
                   IYPGDSDTRYSPSFQGQVTISADKSISTAYLQWSSLKASDTAMYYCARFP 
                 
               
               
                   
               
               
                   YDSSGYYSFDYWGQGTLVTVSS ASTKGPSVFPLAPSSKSTSGGTAALGCL 
               
               
                   
               
               
                 VKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGT 
               
               
                   
               
               
                 QTYICNVNHKPSNTKVDKKVEPKSCDKTHT 
               
               
                   
               
               
                 anti-TfR Fab′ light chain (kappa, VL underlined) 
               
               
                 (SEQ ID NO: 212) 
               
               
                 
                   DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYA 
                 
               
               
                   
               
               
                 
                   ASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGG 
                 
               
               
                   
               
               
                   GTKVEIK RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKV 
               
               
                   
               
               
                 DNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQG 
               
               
                   
               
               
                 LSSPVTKSFNRGEC 
               
            
           
         
       
     
     In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 213 or SEQ ID NO: 777. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising an amino acid sequence that is at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to SEQ ID NO: 212. In some embodiments, the anti-TfR antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 213 or SEQ ID NO: 777. Alternatively or in addition (e.g., in addition), the anti-TfR antibody of the present disclosure comprises a light chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 212. In some embodiments, the anti-TfR antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 213 or SEQ ID NO: 777. Alternatively or in addition (e.g., in addition), the anti-TfR antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 212. 
     In some embodiments, any one of the anti-TfR1 antibodies described herein may comprise a signal peptide in the heavy and/or (e.g., and) light chain sequence (e.g., a N-terminal signal peptide). In some embodiments, the anti-TfR1 antibody described herein comprises any one of the VH and VL sequences, any one of the IgG heavy chain and light chain sequences listed, or any one of the F(ab′) heavy chain and light chain sequences described herein, and further comprises a signal peptide (e.g., a N-terminal signal peptide). In some embodiments, the signal peptide comprises the amino acid sequence of MGWSCIILFLVATATGVHS (SEQ ID NO: 214). 
     Other Known Anti-Transferrin Receptor Antibodies 
     Any other appropriate anti-transferrin receptor antibodies known in the art may be used as the muscle-targeting agent in the complexes disclosed herein. Examples of known anti-transferrin receptor antibodies, including associated references and binding epitopes, are listed in Table 8. In some embodiments, the anti-transferrin receptor antibody comprises the complementarity determining regions (CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3) of any of the anti-transferrin receptor antibodies provided herein, e.g., anti-transferrin receptor antibodies listed in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 List of anti-transferrin receptor antibody clones, including 
               
               
                 associated references and binding epitope information. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Antibody Clone Name 
                 Reference(s) 
                 Epitope/Notes 
               
               
                   
               
               
                 OKT9 
                 U.S. Pat. No. 4,364,934, filed 
                 Apical domain of TfR 
               
               
                   
                 Dec. 4, 1979, entitled 
                 (residues 305-366 of 
               
               
                   
                 “MONOCLONAL ANTIBODY TO 
                 human TfR sequence 
               
               
                   
                 A HUMAN EARLY THYMOCYTE 
                 XM_052730.3, available 
               
               
                   
                 ANTIGEN AND METHODS FOR 
                 in GenBank) 
               
               
                   
                 PREPARING SAME” Schneider 
               
               
                   
                 C. et al. “Structural features 
               
               
                   
                 of the cell surface receptor for 
               
               
                   
                 transferrin that is recognized by 
               
               
                   
                 the monoclonal antibody OKT9.” 
               
               
                   
                 J Biol Chem. 1982, 257: 14, 
               
               
                   
                 8516-8522. 
               
               
                 (From JCR) 
                 WO 2015/098989, filed Dec. 24, 2014, 
                 Apical domain (residues 
               
               
                 Clone M11 
                 “Novel anti-Transferrin receptor 
                 230-244 and 326-347 of TfR) 
               
               
                 Clone M23 
                 antibody that passes through 
                 and protease-like domain 
               
               
                 Clone M27 
                 blood-brain barrier” 
                 (residues 461-473) 
               
               
                 Clone B84 
                 U.S. Pat. No. 9,994,641, filed 
               
               
                   
                 Dec. 24, 2014, “Novel anti- 
               
               
                   
                 Transferrin receptor antibody 
               
               
                   
                 that passes through blood-brain 
               
               
                   
                 barrier” 
               
               
                 (From Genentech) 
                 WO 2016/081643, filed May 26, 2016, 
                 Apical domain and non- 
               
               
                 7A4, 8A2, 15D2, 10D11, 
                 entitled “ANTI-TRANSFERRIN 
                 apical regions 
               
               
                 7B10, 15G11, 16G5, 13C3, 
                 RECEPTOR ANTIBODIES AND 
               
               
                 16G4, 16F6, 7G7, 4C2, 
                 METHODS OF USE” 
               
               
                 1B12, and 13D4 
                 U.S. Pat. No. 9,708,406, filed 
               
               
                   
                 May 20, 2014, “Anti-transferrin 
               
               
                   
                 receptor antibodies and methods of use” 
               
               
                 (From Armagen) 
                 Lee et al. “Targeting Rat Anti-Mouse 
               
               
                 8D3 
                 Transferrin Receptor Monoclonal 
               
               
                   
                 Antibodies through Blood-Brain Barrier 
               
               
                   
                 in Mouse” 2000, J Pharmacol. Exp. 
               
               
                   
                 Ther., 292: 1048-1052. 
               
               
                   
                 U.S. Pat. App. 2010/077498, filed 
               
               
                   
                 Sep. 11, 2008, entitled “COMPOSITIONS 
               
               
                   
                 AND METHODS FOR BLOOD-BRAIN 
               
               
                   
                 BARRIER DELIVERY IN THE MOUSE” 
               
               
                 OX26 
                 Haobam, B. et al. 2014. Rab17-mediated 
               
               
                   
                 recycling endosomes contribute to 
               
               
                   
                 autophagosome formation in response 
               
               
                   
                 to Group A  Streptococcus  invasion. 
               
               
                   
                 Cellular microbiology. 16: 1806-21. 
               
               
                 DF1513 
                 Ortiz-Zapater E et al. Trafficking of 
               
               
                   
                 the human transferrin receptor 
               
               
                   
                 in plant cells: effects of tyrphostin 
               
               
                   
                 A23 and brefeldin A. Plant J 48: 757- 
               
               
                   
                 70 (2006). 
               
               
                 1A1B2, 66IG10, MEM-189, JF0956, 
                 Commercially available anti- 
                 Novus Biologicals 8100 
               
               
                 29806, 1A1B2, TFRC/1818, 1E6, 
                 transferrin receptor antibodies. 
                 Southpark Way, A-8 
               
               
                 66Ig10, TFRC/1059, Q1/71, 23D10, 
                   
                 Littleton CO 80120 
               
               
                 13E4, TFRC/1149, ER-MP21, 
               
               
                 YTA74.4, BU54, 2B6, RI7 217 
               
               
                 (From INSERM) 
                 U.S. Pat. App. 2011/0311544A1, filed 
                 Does not compete with OKT9 
               
               
                 BA120g 
                 Jun. 15, 2005, entitled “ANTI-CD71 
               
               
                   
                 MONOCLONAL ANTIBODIES 
               
               
                   
                 AND USES THEREOF FOR 
               
               
                   
                 TREATING MALIGNANT TUMOR CELLS” 
               
               
                 LUCA31 
                 U.S. Pat. No. 7,572,895, filed 
                 “LUCA31 epitope” 
               
               
                   
                 Jun. 7, 2004, entitled “TRANSFERRIN 
               
               
                   
                 RECEPTOR ANTIBODIES” 
               
               
                 (Salk Institute) 
                 Trowbridge, I. S. et al. “Anti- 
               
               
                 B3/25 
                 transferrin receptor monoclonal 
               
               
                 T58/30 
                 antibody and toxin-antibody conjugates 
               
               
                   
                 affect growth of human tumour cells.” 
               
               
                   
                 Nature, 1981, volume 294, pages 171-173 
               
               
                 R17 217.1.3, 
                 Commercially available anti-transferrin 
                 BioXcell 10 Technology Dr., 
               
               
                 5E9C11, 
                 receptor antibodies. 
                 Suite 2B West Lebanon, NH 
               
               
                 OKT9 (BE0023 clone) 
                   
                 03784-1671 USA 
               
               
                 BK19.9, B3/25, 
                 Gatter, K. C. et al. “Transferrin 
               
               
                 T56/14 and T58/1 
                 receptors in human tissues: their 
               
               
                   
                 distribution and possible clinical 
               
               
                   
                 relevance.” J Clin Pathol. 1983 May; 
               
               
                   
                 36(5): 539-45. 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Anti-TfR antibody 15G11 
               
               
                   
                 CDRs listed in Table 9 
               
               
                   
                 VH (SEQ ID NO: 230) 
               
               
                   
                 VL (SEQ ID NO: 231) 
               
               
                   
                 Fab′ HC (SEQ ID NO: 240) 
               
               
                   
                 Fab′ LC (SEQ ID NO: 237) 
               
               
                   
                 Anti-TfR antibody 
               
               
                   
                 CDRH1 (SEQ ID NO: 3870) 
               
               
                   
                 CDRH2 (SEQ ID NO: 3871) 
               
               
                   
                 CDRH3 (SEQ ID NO: 3872) 
               
               
                   
                 CDRL1 (SEQ ID NO: 3873) 
               
               
                   
                 CDRL2 (SEQ ID NO: 3874) 
               
               
                   
                 CDRL3 (SEQ ID NO: 3875) 
               
               
                   
                 VH (SEQ ID NO: 3876) 
               
               
                   
                 VL(SEQ ID NO: 3877) 
               
               
                   
                   
               
            
           
           
               
            
               
                 Additional Anti-TfR SEQ ID NOs 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 VH/VL 
                 CDR1 
                 CDR2 
                 CDR3 
               
               
                   
                   
               
               
                   
                 VH1 
                 3886 
                 3878 
                 3879 
                 3872 
               
               
                   
                 VH2 
                 3887 
                 3878 
                 3880 
                 3872 
               
               
                   
                 VH3 
                 3888 
                 3878 
                 3881 
                 3872 
               
               
                   
                 VH4 
                 3889 
                 3878 
                 3880 
                 3872 
               
               
                   
                 VL1 
                 3890 
                 3873 
                 3874 
                 3882 
               
               
                   
                 VL2 
                 3891 
                 3873 
                 3874 
                 3882 
               
               
                   
                 VL3 
                 3892 
                 3873 
                 3883 
                 3875 
               
               
                   
                 VL4 
                 3893 
                 3884 
                 3885 
                 3875 
               
               
                   
                   
               
            
           
         
       
     
     In some embodiments, transferrin receptor antibodies of the present disclosure include one or more of the CDR-H (e.g., CDR-H1, CDR-H2, and CDR-H3) amino acid sequences from any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, transferrin receptor antibodies include the CDR-H1, CDR-H2, and CDR-H3 as provided for any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, anti-transferrin receptor antibodies include the CDR-L1, CDR-L2, and CDR-L3 as provided for any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, anti-transferrin antibodies include the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 as provided for any one of the anti-transferrin receptor antibodies selected from Table 8. The disclosure also includes any nucleic acid sequence that encodes a molecule comprising a CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, or CDR-L3 as provided for any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, antibody heavy and light chain CDR3 domains may play a particularly important role in the binding specificity/affinity of an antibody for an antigen. Accordingly, anti-transferrin receptor antibodies of the disclosure may include at least the heavy and/or (e.g., and) light chain CDR3s of any one of the anti-transferrin receptor antibodies selected from Table 8. 
     In some examples, any of the anti-transferrin receptor antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any of the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and/or (e.g., and) CDR-L3 sequences from one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the position of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary by one, two, three, four, five, or six amino acid positions so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). For example, in some embodiments, the position defining a CDR of any antibody described herein can vary by shifting the N-terminal and/or (e.g., and) C-terminal boundary of the CDR by one, two, three, four, five, or six amino acids, relative to the CDR position of any one of the antibodies described herein, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). In another embodiment, the length of one or more CDRs along the VH (e.g., CDR-H1, CDR-H2, or CDR-H3) and/or (e.g., and) VL (e.g., CDR-L1, CDR-L2, or CDR-L3) region of an antibody described herein can vary (e.g., be shorter or longer) by one, two, three, four, five, or more amino acids, so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% of the binding of the original antibody from which it is derived). 
     Accordingly, in some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids shorter than one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein may be one, two, three, four, five or more amino acids longer than one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be extended by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the amino portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, the carboxy portion of a CDR-L1, CDR-L2, CDR-L3, CDR-H1, CDR-H2, and/or (e.g., and) CDR-H3 described herein can be shortened by one, two, three, four, five or more amino acids compared to one or more of the CDRs described herein (e.g., CDRS from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). Any method can be used to ascertain whether immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained, for example, using binding assays and conditions described in the art. 
     In some examples, any of the anti-transferrin receptor antibodies of the disclosure have one or more CDR (e.g., CDR-H or CDR-L) sequences substantially similar to any one of the anti-transferrin receptor antibodies selected from Table 8. For example, the antibodies may include one or more CDR sequence(s) from any of the anti-transferrin receptor antibodies selected from Table 8 containing up to 5, 4, 3, 2, or 1 amino acid residue variations as compared to the corresponding CDR region in any one of the CDRs provided herein (e.g., CDRs from any of the anti-transferrin receptor antibodies selected from Table 8) so long as immunospecific binding to transferrin receptor (e.g., human transferrin receptor) is maintained (e.g., substantially maintained, for example, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% relative to the binding of the original antibody from which it is derived). In some embodiments, any of the amino acid variations in any of the CDRs provided herein may be conservative variations. Conservative variations can be introduced into the CDRs at positions where the residues are not likely to be involved in interacting with a transferrin receptor protein (e.g., a human transferrin receptor protein), for example, as determined based on a crystal structure. Some aspects of the disclosure provide transferrin receptor antibodies that comprise one or more of the heavy chain variable (VH) and/or (e.g., and) light chain variable (VL) domains provided herein. In some embodiments, any of the VH domains provided herein include one or more of the CDR-H sequences (e.g., CDR-H1, CDR-H2, and CDR-H3) provided herein, for example, any of the CDR-H sequences provided in any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, any of the VL domains provided herein include one or more of the CDR-L sequences (e.g., CDR-L1, CDR-L2, and CDR-L3) provided herein, for example, any of the CDR-L sequences provided in any one of the anti-transferrin receptor antibodies selected from Table 8. 
     In some embodiments, anti-transferrin receptor antibodies of the disclosure include any antibody that includes a heavy chain variable domain and/or (e.g., and) a light chain variable domain of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, anti-transferrin receptor antibodies of the disclosure include any antibody that includes the heavy chain variable and light chain variable pairs of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. 
     Aspects of the disclosure provide anti-transferrin receptor antibodies having a heavy chain variable (VH) and/or (e.g., and) a light chain variable (VL) domain amino acid sequence homologous to any of those described herein. In some embodiments, the anti-transferrin receptor antibody comprises a heavy chain variable sequence or a light chain variable sequence that is at least 75% (e.g., 80%, 85%, 90%, 95%, 98%, or 99%) identical to the heavy chain variable sequence and/or any light chain variable sequence of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the homologous heavy chain variable and/or (e.g., and) a light chain variable amino acid sequences do not vary within any of the CDR sequences provided herein. For example, in some embodiments, the degree of sequence variation (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) may occur within a heavy chain variable and/or (e.g., and) a light chain variable sequence excluding any of the CDR sequences provided herein. In some embodiments, any of the anti-transferrin receptor antibodies provided herein comprise a heavy chain variable sequence and a light chain variable sequence that comprises a framework sequence that is at least 75%, 80%, 85%, 90%, 95%, 98%, or 99% identical to the framework sequence of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. 
     In some embodiments, an anti-transferrin receptor antibody, which specifically binds to transferrin receptor (e.g., human transferrin receptor), comprises a light chain variable VL domain comprising any of the CDR-L domains (CDR-L1, CDR-L2, and CDR-L3), or CDR-L domain variants provided herein, of any of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, an anti-transferrin receptor antibody, which specifically binds to transferrin receptor (e.g., human transferrin receptor), comprises a light chain variable VL domain comprising the CDR-L1, the CDR-L2, and the CDR-L3 of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the anti-transferrin receptor antibody comprises a light chain variable (VL) region sequence comprising one, two, three or four of the framework regions of the light chain variable region sequence of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the anti-transferrin receptor antibody comprises one, two, three or four of the framework regions of a light chain variable region sequence which is at least 75%, 80%, 85%, 90%, 95%, or 100% identical to one, two, three or four of the framework regions of the light chain variable region sequence of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the light chain variable framework region that is derived from said amino acid sequence consists of said amino acid sequence but for the presence of up to 10 amino acid substitutions, deletions, and/or (e.g., and) insertions, preferably up to 10 amino acid substitutions. In some embodiments, the light chain variable framework region that is derived from said amino acid sequence consists of said amino acid sequence with 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acid residues being substituted for an amino acid found in an analogous position in a corresponding non-human, primate, or human light chain variable framework region. 
     In some embodiments, an anti-transferrin receptor antibody that specifically binds to transferrin receptor comprises the CDR-L1, the CDR-L2, and the CDR-L3 of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the antibody further comprises one, two, three or all four VL framework regions derived from the VL of a human or primate antibody. The primate or human light chain framework region of the antibody selected for use with the light chain CDR sequences described herein, can have, for example, at least 70% (e.g., at least 75%, 80%, 85%, 90%, 95%, 98%, or at least 99%) identity with a light chain framework region of a non-human parent antibody. The primate or human antibody selected can have the same or substantially the same number of amino acids in its light chain complementarity determining regions to that of the light chain complementarity determining regions of any of the antibodies provided herein, e.g., any of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, the primate or human light chain framework region amino acid residues are from a natural primate or human antibody light chain framework region having at least 75% identity, at least 80% identity, at least 85% identity, at least 90% identity, at least 95% identity, at least 98% identity, at least 99% (or more) identity with the light chain framework regions of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. In some embodiments, an anti-transferrin receptor antibody further comprises one, two, three or all four VL framework regions derived from a human light chain variable kappa subfamily. In some embodiments, an anti-transferrin receptor antibody further comprises one, two, three or all four VL framework regions derived from a human light chain variable lambda subfamily. 
     In some embodiments, any of the anti-transferrin receptor antibodies provided herein comprise a light chain variable domain that further comprises a light chain constant region. In some embodiments, the light chain constant region is a kappa, or a lambda light chain constant region. In some embodiments, the kappa or lambda light chain constant region is from a mammal, e.g., from a human, monkey, rat, or mouse. In some embodiments, the light chain constant region is a human kappa light chain constant region. In some embodiments, the light chain constant region is a human lambda light chain constant region. It should be appreciated that any of the light chain constant regions provided herein may be variants of any of the light chain constant regions provided herein. In some embodiments, the light chain constant region comprises an amino acid sequence that is at least 75%, 80%, 85%, 90%, 95%, 98%, or 99% identical to any of the light chain constant regions of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. 
     In some embodiments, the anti-transferrin receptor antibody is any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8. 
     In some embodiments, an anti-transferrin receptor antibody comprises a VL domain comprising the amino acid sequence of any anti-transferrin receptor antibody, such as any one of the anti-transferrin receptor antibodies selected from Table 8, and wherein the constant regions comprise the amino acid sequences of the constant regions of an IgG, IgE, IgM, IgD, IgA or IgY immunoglobulin molecule, or a human IgG, IgE, IgM, IgD, IgA or IgY immunoglobulin molecule. In some embodiments, an anti-transferrin receptor antibody comprises any of the VL domains, or VL domain variants, and any of the VH domains, or VH domain variants, wherein the VL and VH domains, or variants thereof, are from the same antibody clone, and wherein the constant regions comprise the amino acid sequences of the constant regions of an IgG, IgE, IgM, IgD, IgA or IgY immunoglobulin molecule, any class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2), or any subclass (e.g., IgG2a and IgG2b) of immunoglobulin molecule. Non-limiting examples of human constant regions are described in the art, e.g., see Kabat E A et al., (1991) supra. 
     In some embodiments, the muscle-targeting agent is a transferrin receptor antibody (e.g., the antibody and variants thereof as described in International Application Publication WO 2016/081643, incorporated herein by reference). 
     The heavy chain and light chain CDRs of the antibody according to different definition systems are provided in Table 9. The different definition systems, e.g., the Kabat definition, the Chothia definition, and/or (e.g., and) the contact definition have been described. See, e.g., (e.g., Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242, Chothia et al., (1989) Nature 342:877; Chothia, C. et al. (1987) J. Mol. Biol. 196:901-917, Al-lazikani et al (1997) J. Molec. Biol. 273:927-948; and Almagro, J. Mol. Recognit. 17:132-143 (2004). See also hgmp.mrc.ac.uk and bioinf.org.uk/abs). 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Heavy chain and light chain CDRs of a mouse transferrin receptor antibody 
               
            
           
           
               
               
               
               
            
               
                 CDRs 
                 Kabat 
                 Chothia 
                 Contact 
               
               
                   
               
               
                 CDR-H1 
                 SYWMH (SEQ ID NO: 
                 GYTFTSY (SEQ ID NO: 
                 TSYWMH (SEQ ID NO: 
               
               
                   
                 216) 
                 222) 
                 224) 
               
               
                   
               
               
                 CDR-H2 
                 EINPTNGRTNYIEKFKS 
                 NPTNGR (SEQ ID NO: 
                 WIGEINPTNGRTN 
               
               
                   
                 (SEQ ID NO: 217) 
                 223) 
                 (SEQ ID NO: 225) 
               
               
                   
               
               
                 CDR-H3 
                 GTRAYHY (SEQ ID 
                 GTRAYHY (SEQ ID 
                 ARGTRA (SEQ ID NO: 
               
               
                   
                 NO: 218) 
                 NO: 218) 
                 226) 
               
               
                   
               
               
                 CDR-L1 
                 RASDNLYSNLA (SEQ 
                 RASDNLYSNLA (SEQ 
                 YSNLAWY (SEQ ID 
               
               
                   
                 ID NO: 219) 
                 ID NO: 219) 
                 NO: 227) 
               
               
                   
               
               
                 CDR-L2 
                 DATNLAD (SEQ ID NO: 
                 DATNLAD (SEQ ID NO: 
                 LLVYDATNLA (SEQ ID 
               
               
                   
                 220) 
                 220) 
                 NO: 228) 
               
               
                   
               
               
                 CDR-L3 
                 QHFWGTPLT (SEQ ID 
                 QHFWGTPLT (SEQ ID 
                 QHFWGTPL (SEQ ID 
               
               
                   
                 NO: 221) 
                 NO: 221) 
                 NO: 229) 
               
               
                   
               
            
           
         
       
     
     The heavy chain variable domain (VH) and light chain variable domain sequences are also provided: 
     
       
         
           
               
            
               
                 VH 
               
               
                 (SEQ ID NO: 230) 
               
               
                 QVQLQQPGAELVKPGASVKLSCKASGYTFTSYWMHWVKQRPGQGLEWIG 
               
               
                 EINPTNGRTNYIEKFKSKATLTVDKSSSTAYMQLSSLTSEDSAVYYCAR 
               
               
                 GTRAYHYWGQGTSVTVSS 
               
               
                   
               
               
                 VL 
               
               
                 (SEQ ID NO: 231) 
               
               
                 DIQMTQSPASLSVSVGETVTITCRASDNLYSNLAWYQQKQGKSPQLLVY 
               
               
                 DATNLADGVPSRFSGSGSGTQYSLKINSLQSEDFGTYYCQHFWGTPLTF 
               
               
                 GAGTKLELK 
               
            
           
         
       
     
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 9. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a CDR-L1, a CDR-L2, and a CDR-L3 that are the same as the CDR-L1, CDR-L2, and CDR-L3 shown in Table 9. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2, or 1 amino acid variation) as compared with the CDR-H1, CDR-H2, and CDR-H3 as shown in Table 9. “Collectively” means that the total number of amino acid variations in all of the three heavy chain CDRs is within the defined range. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure may comprise a CDR-L1, a CDR-L2, and a CDR-L3, which collectively contains no more than 5 amino acid variations (e.g., no more than 5, 4, 3, 2 or 1 amino acid variation) as compared with the CDR-L1, CDR-L2, and CDR-L3 as shown in Table 9. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-H1, a CDR-H2, and a CDR-H3, at least one of which contains no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the counterpart heavy chain CDR as shown in Table 9. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure may comprise CDR-L1, a CDR-L2, and a CDR-L3, at least one of which contains no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the counterpart light chain CDR as shown in Table 9. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-L3, which contains no more than 3 amino acid variations (e.g., no more than 3, 2, or 1 amino acid variation) as compared with the CDR-L3 as shown in Table 9. In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-L3 containing one amino acid variation as compared with the CDR-L3 as shown in Table 9. In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-L3 of QHFAGTPLT (SEQ ID NO: 232) according to the Kabat and Chothia definition system) or QHFAGTPL (SEQ ID NO: 233) according to the Contact definition system). In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1 and a CDR-L2 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 9, and comprises a CDR-L3 of QHFAGTPLT (SEQ ID NO: 232) according to the Kabat and Chothia definition system) or QHFAGTPL (SEQ ID NO: 233) according to the Contact definition system). 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises heavy chain CDRs that collectively are at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the heavy chain CDRs as shown in Table 9. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises light chain CDRs that collectively are at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the light chain CDRs as shown in Table 9. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 230. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 231. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 230. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL containing no more than 15 amino acid variations (e.g., no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 231. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the VH as set forth in SEQ ID NO: 230. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the VL as set forth in SEQ ID NO: 231. 
     In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized antibody (e.g., a humanized variant of an antibody). In some embodiments, the transferrin receptor antibody of the present disclosure comprises a CDR-H1, a CDR-H2, a CDR-H3, a CDR-L1, a CDR-L2, and a CDR-L3 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 9, and comprises a humanized heavy chain variable region and/or (e.g., and) a humanized light chain variable region. 
     Humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, or rabbit having the desired specificity, affinity, and capacity. In some embodiments, Fv framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, the humanized antibody may comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences, but are included to further refine and optimize antibody performance. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region or domain (Fc), typically that of a human immunoglobulin. Antibodies may have Fc regions modified as described in WO 99/58572. Other forms of humanized antibodies have one or more CDRs (one, two, three, four, five, six) which are altered with respect to the original antibody, which are also termed one or more CDRs derived from one or more CDRs from the original antibody. Humanized antibodies may also involve affinity maturation. 
     In some embodiments, humanization is achieved by grafting the CDRs (e.g., as shown in Table 9) into the IGKV1-NL1*01 and IGHV1-3*01 human variable domains. In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized variant comprising one or more amino acid substitutions at positions 9, 13, 17, 18, 40, 45, and 70 as compared with the VL as set forth in SEQ ID NO: 231, and/or (e.g., and) one or more amino acid substitutions at positions 1, 5, 7, 11, 12, 20, 38, 40, 44, 66, 75, 81, 83, 87, and 108 as compared with the VH as set forth in SEQ ID NO: 230. In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized variant comprising amino acid substitutions at all of positions 9, 13, 17, 18, 40, 45, and 70 as compared with the VL as set forth in SEQ ID NO: 231, and/or (e.g., and) amino acid substitutions at all of positions 1, 5, 7, 11, 12, 20, 38, 40, 44, 66, 75, 81, 83, 87, and 108 as compared with the VH as set forth in SEQ ID NO: 230. 
     In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized antibody and contains the residues at positions 43 and 48 of the VL as set forth in SEQ ID NO: 231. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure is a humanized antibody and contains the residues at positions 48, 67, 69, 71, and 73 of the VH as set forth in SEQ ID NO: 230. 
     The VH and VL amino acid sequences of an example humanized antibody that may be used in accordance with the present disclosure are provided: 
     
       
         
           
               
            
               
                 Humanized VH 
               
               
                 (SEQ ID NO: 234) 
               
               
                 EVQLVQSGAEVKKPGASVKVSCKASGYTFTSYWMHWVRQAPGQRLEWIG 
               
               
                 EINPTNGRTNYIEKFKSRATLTVDKSASTAYMELSSLRSEDTAVYYCAR 
               
               
                 GTRAYHYWGQGTMVTVSS 
               
               
                   
               
               
                 Humanized VL 
               
               
                 (SEQ ID NO: 235) 
               
               
                 DIQMTQSPSSLSASVGDRVTITCRASDNLYSNLAWYQQKPGKSPKLLVY 
               
               
                 DATNLADGVPSRFSGSGSGTDYTLTISSLQPEDFATYYCQHFWGTPLTF 
               
               
                 GQGTKVEIK 
               
            
           
         
       
     
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 234. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 235. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VH as set forth in SEQ ID NO: 234. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL containing no more than 15 amino acid variations (e.g., no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the VL as set forth in SEQ ID NO: 235. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a VH comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the VH as set forth in SEQ ID NO: 234. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a VL comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the VL as set forth in SEQ ID NO: 235. 
     In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized variant comprising amino acid substitutions at one or more of positions 43 and 48 as compared with the VL as set forth in SEQ ID NO: 231, and/or (e.g., and) amino acid substitutions at one or more of positions 48, 67, 69, 71, and 73 as compared with the VH as set forth in SEQ ID NO: 230. In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized variant comprising a S43A and/or (e.g., and) a V48L mutation as compared with the VL as set forth in SEQ ID NO: 231, and/or (e.g., and) one or more of A67V, L69I, V71R, and K73T mutations as compared with the VH as set forth in SEQ ID NO: 230 
     In some embodiments, the transferrin receptor antibody of the present disclosure is a humanized variant comprising amino acid substitutions at one or more of positions 9, 13, 17, 18, 40, 43, 48, 45, and 70 as compared with the VL as set forth in SEQ ID NO: 231, and/or (e.g., and) amino acid substitutions at one or more of positions 1, 5, 7, 11, 12, 20, 38, 40, 44, 48, 66, 67, 69, 71, 73, 75, 81, 83, 87, and 108 as compared with the VH as set forth in SEQ ID NO: 230. 
     In some embodiments, the transferrin receptor antibody of the present disclosure is a chimeric antibody, which can include a heavy constant region and a light constant region from a human antibody. Chimeric antibodies refer to antibodies having a variable region or part of variable region from a first species and a constant region from a second species. Typically, in these chimeric antibodies, the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals (e.g., a non-human mammal such as mouse, rabbit, and rat), while the constant portions are homologous to the sequences in antibodies derived from another mammal such as human. In some embodiments, amino acid modifications can be made in the variable region and/or (e.g., and) the constant region. 
     In some embodiments, the transferrin receptor antibody described herein is a chimeric antibody, which can include a heavy constant region and a light constant region from a human antibody. Chimeric antibodies refer to antibodies having a variable region or part of variable region from a first species and a constant region from a second species. Typically, in these chimeric antibodies, the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals (e.g., a non-human mammal such as mouse, rabbit, and rat), while the constant portions are homologous to the sequences in antibodies derived from another mammal such as human. In some embodiments, amino acid modifications can be made in the variable region and/or (e.g., and) the constant region. 
     In some embodiments, the heavy chain of any of the transferrin receptor antibodies as described herein may comprises a heavy chain constant region (CH) or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof). The heavy chain constant region can of any suitable origin, e.g., human, mouse, rat, or rabbit. In one specific example, the heavy chain constant region is from a human IgG (a gamma heavy chain), e.g., IgG1, IgG2, or IgG4. An example of human IgG1 constant region is given below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 175) 
               
               
                 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSG 
               
               
                   
               
               
                 VHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKV 
               
               
                   
               
               
                 EPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV 
               
               
                   
               
               
                 DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDW 
               
               
                   
               
               
                 LNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQ 
               
               
                   
               
               
                 VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLT 
               
               
                   
               
               
                 VDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK  
               
            
           
         
       
     
     In some embodiments, the light chain of any of the transferrin receptor antibodies described herein may further comprise a light chain constant region (CL), which can be any CL known in the art. In some examples, the CL is a kappa light chain. In other examples, the CL is a lambda light chain. In some embodiments, the CL is a kappa light chain, the sequence of which is provided below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 177) 
               
               
                 RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQS 
               
               
                 GNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPV  
               
               
                 TKSFNRGEC 
               
            
           
         
       
     
     Other antibody heavy and light chain constant regions are well known in the art, e.g., those provided in the IMGT database (www.imgt.org) or at www.vbase2.org/vbstat.php., both of which are incorporated by reference herein. 
     Examples of heavy chain and light chain amino acid sequences of the transferrin receptor antibodies described are provided below: 
     
       
         
           
               
            
               
                 Heavy Chain (VH + human IgG1 constant region) 
               
               
                 (SEQ ID NO: 236) 
               
               
                 QVQLQQPGAELVKPGASVKLSCKASGYTFTSYWMHWVKQRPGQGLEWIG 
               
               
                   
               
               
                 EINPTNGRTNYIEKFKSKATLTVDKSSSTAYMQLSSLTSEDSAVYYCAR 
               
               
                   
               
               
                 GTRAYHYWGQGTSVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKD 
               
               
                   
               
               
                 YFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT 
               
               
                   
               
               
                 YICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPK 
               
               
                   
               
               
                 PKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQ 
               
               
                   
               
               
                 YNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPR 
               
               
                   
               
               
                 EPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKT 
               
               
                   
               
               
                 TPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLS 
               
               
                   
               
               
                 LSPGK 
               
               
                   
               
               
                 Light Chain (VL + kappa light chain) 
               
               
                 (SEQ ID NO: 237) 
               
               
                 DIQMTQSPASLSVSVGETVTITCRASDNLYSNLAWYQQKQGKSPQLLVY 
               
               
                   
               
               
                 DATNLADGVPSRFSGSGSGTQYSLKINSLQSEDFGTYYCQHFWGTPLTF 
               
               
                   
               
               
                 GAGTKLELKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQ 
               
               
                   
               
               
                 WKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEV 
               
               
                   
               
               
                 THQGLSSPVTKSFNRGEC 
               
               
                   
               
               
                 Heavy Chain (humanized VH + human IgG1 constant 
               
               
                 region) 
               
               
                 (SEQ ID NO: 238) 
               
               
                 EVQLVQSGAEVKKPGASVKVSCKASGYTFTSYWMHWVRQAPGQRLEWIG 
               
               
                   
               
               
                 EINPTNGRTNYIEKFKSRATLTVDKSASTAYMELSSLRSEDTAVYYCAR 
               
               
                   
               
               
                 GTRAYHYWGQGTMVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKD 
               
               
                   
               
               
                 YFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT 
               
               
                   
               
               
                 YICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPK 
               
               
                   
               
               
                 PKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQ 
               
               
                   
               
               
                 YNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPR 
               
               
                   
               
               
                 EPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKT 
               
               
                   
               
               
                 TPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLS 
               
               
                   
               
               
                 LSPGK 
               
               
                   
               
               
                 Light Chain (humanized VL + kappa light chain) 
               
               
                 (SEQ ID NO: 239) 
               
               
                 DIQMTQSPSSLSASVGDRVTITCRASDNLYSNLAWYQQKPGKSPKLLVY 
               
               
                   
               
               
                 DATNLADGVPSRFSGSGSGTDYTLTISSLQPEDFATYYCQHFWGTPLTF 
               
               
                   
               
               
                 GQGTKVEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQ 
               
               
                   
               
               
                 WKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEV 
               
               
                   
               
               
                 THQGLSSPVTKSFNRGEC 
               
            
           
         
       
     
     In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to SEQ ID NO: 236. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to SEQ ID NO: 237. In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 236. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 237. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain as set forth in SEQ ID NO: 236. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a light chain containing no more than 15 amino acid variations (e.g., no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain as set forth in SEQ ID NO: 237. 
     In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to SEQ ID NO: 238. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising an amino acid sequence that is at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to SEQ ID NO: 239. In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 238. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 239. 
     In some embodiments, the transferrin receptor antibody of the present disclosure comprises a heavy chain containing no more than 25 amino acid variations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the heavy chain of humanized antibody as set forth in SEQ ID NO: 238. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody of the present disclosure comprises a light chain containing no more than 15 amino acid variations (e.g., no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid variation) as compared with the light chain of humanized antibody as set forth in SEQ ID NO: 239. 
     In some embodiments, the transferrin receptor antibody is an antigen binding fragment (FAB) of an intact antibody (full-length antibody). Antigen binding fragment of an intact antibody (full-length antibody) can be prepared via routine methods. For example, F(ab′)2 fragments can be produced by pepsin digestion of an antibody molecule, and Fab fragments that can be generated by reducing the disulfide bridges of F(ab′)2 fragments. Examples of FABs amino acid sequences of the transferrin receptor antibodies described herein are provided below: 
     
       
         
           
               
            
               
                 Heavy Chain FAB (VH + a portion of human IgG1 
               
               
                 constant region) 
               
               
                 (SEQ ID NO: 240) 
               
               
                 QVQLQQPGAELVKPGASVKLSCKASGYTFTSYWMHWVKQRPGQGLEWIG 
               
               
                   
               
               
                 EINPTNGRTNYIEKFKSKATLTVDKSSSTAYMQLSSLTSEDSAVYYCAR 
               
               
                   
               
               
                 GTRAYHYWGQGTSVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKD 
               
               
                   
               
               
                 YFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT 
               
               
                   
               
               
                 YICNVNHKPSNTKVDKKVEPKSCDKTHTCP 
               
               
                   
               
               
                 Heavy Chain FAB (humanized VH + a portion of 
               
               
                 human IgG1 constant region) 
               
               
                 (SEQ ID NO: 241) 
               
               
                 EVQLVQSGAEVKKPGASVKVSCKASGYTFTSYWMHWVRQAPGQRLEWIG 
               
               
                   
               
               
                 EINPTNGRTNYIEKFKSRATLTVDKSASTAYMELSSLRSEDTAVYYCAR 
               
               
                   
               
               
                 GTRAYHYWGQGTMVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKD 
               
               
                   
               
               
                 YFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT 
               
               
                   
               
               
                 YICNVNHKPSNTKVDKKVEPKSCDKTHTCP 
               
            
           
         
       
     
     In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 240. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 237. 
     In some embodiments, the transferrin receptor antibody described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 241. Alternatively or in addition (e.g., in addition), the transferrin receptor antibody described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 239. 
     The transferrin receptor antibodies described herein can be in any antibody form, including, but not limited to, intact (i.e., full-length) antibodies, antigen-binding fragments thereof (such as Fab, Fab′, F(ab′)2, Fv), single chain antibodies, bi-specific antibodies, or nanobodies. In some embodiments, the transferrin receptor antibody described herein is a scFv. In some embodiments, the transferrin receptor antibody described herein is a scFv-Fab (e.g., scFv fused to a portion of a constant region). In some embodiments, the transferrin receptor antibody described herein is a scFv fused to a constant region (e.g., human IgG1 constant region as set forth in SEQ ID NO: 175). 
     In some embodiments, the anti-TfR antibody of the present disclosure is a humanized antibody comprising human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the anti-TfR antibody of the present disclosure is an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the anti-TfR antibody of the present disclosure is a Fab′ fragment of an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 1 or Table 3 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the anti-TfR antibody of the present disclose comprises the CDRs of the antibody provided in Table 7. In some embodiments, the anti-TfR antibody of the present disclosure is an IgG1 kappa that comprises the variable regions of the antibody provided in Table 7. In some embodiments, the anti-TfR antibody of the present disclosure is a Fab′ fragment of an IgG1 kappa that comprises the variable regions of the antibody provided in Table 7. 
     In some embodiments, any one of the anti-TfR antibodies described herein is produced by recombinant DNA technology in Chinese hamster ovary (CHO) cell suspension culture, optionally in CHO-K1 cell (e.g., CHO-K1 cells derived from European Collection of Animal Cell Culture, Cat. No. 85051005) suspension culture. 
     In some embodiments, an antibody provided herein may have one or more post-translational modifications. In some embodiments, N-terminal cyclization, also called pyroglutamate formation (pyro-Glu), may occur in the antibody at N-terminal Glutamate (Glu) and/or Glutamine (Gln) residues during production. In some embodiments, pyroglutamate formation occurs in a heavy chain sequence. In some embodiments, pyroglutamate formation occurs in a light chain sequence. 
     b. Other Muscle-Targeting Antibodies 
     In some embodiments, the muscle-targeting antibody is an antibody that specifically binds hemojuvelin, caveolin-3, Duchenne muscular dystrophy peptide, myosin Iib, or CD63. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds a myogenic precursor protein. Exemplary myogenic precursor proteins include, without limitation, ABCG2, M-Cadherin/Cadherin-15, Caveolin-1, CD34, FoxK1, Integrin alpha 7, Integrin alpha 7 beta 1, MYF-5, MyoD, Myogenin, NCAM-1/CD56, Pax3, Pax7, and Pax9. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds a skeletal muscle protein. Exemplary skeletal muscle proteins include, without limitation, alpha-Sarcoglycan, beta-Sarcoglycan, Calpain Inhibitors, Creatine Kinase MM/CKMM, eIF5A, Enolase 2/Neuron-specific Enolase, epsilon-Sarcoglycan, FABP3/H-FABP, GDF-8/Myostatin, GDF-11/GDF-8, Integrin alpha 7, Integrin alpha 7 beta 1, Integrin beta 1/CD29, MCAM/CD146, MyoD, Myogenin, Myosin Light Chain Kinase Inhibitors, NCAM-1/CD56, and Troponin I. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds a smooth muscle protein. Exemplary smooth muscle proteins include, without limitation, alpha-Smooth Muscle Actin, VE-Cadherin, Caldesmon/CALD1, Calponin 1, Desmin, Histamine H2 R, Motilin R/GPR38, Transgelin/TAGLN, and Vimentin. However, it should be appreciated that antibodies to additional targets are within the scope of this disclosure and the exemplary lists of targets provided herein are not meant to be limiting. 
     c. Antibody Features/Alterations 
     In some embodiments, conservative mutations can be introduced into antibody sequences (e.g., CDRs or framework sequences) at positions where the residues are not likely to be involved in interacting with a target antigen (e.g., transferrin receptor), for example, as determined based on a crystal structure. In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region of a muscle-targeting antibody described herein (e.g., in a CH2 domain (residues 231-340 of human IgG1) and/or (e.g., and) CH3 domain (residues 341-447 of human IgG1) and/or (e.g., and) the hinge region, with numbering according to the Kabat numbering system (e.g., the EU index in Kabat)) to alter one or more functional properties of the antibody, such as serum half-life, complement fixation, Fc receptor binding and/or (e.g., and) antigen-dependent cellular cytotoxicity. 
     In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the hinge region of the Fc region (CH1 domain) such that the number of cysteine residues in the hinge region are altered (e.g., increased or decreased) as described in, e.g., U.S. Pat. No. 5,677,425. The number of cysteine residues in the hinge region of the CH1 domain can be altered to, e.g., facilitate assembly of the light and heavy chains, or to alter (e.g., increase or decrease) the stability of the antibody or to facilitate linker conjugation. 
     In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region of a muscle-targeting antibody described herein (e.g., in a CH2 domain (residues 231-340 of human IgG1) and/or (e.g., and) CH3 domain (residues 341-447 of human IgG1) and/or (e.g., and) the hinge region, with numbering according to the Kabat numbering system (e.g., the EU index in Kabat)) to increase or decrease the affinity of the antibody for an Fc receptor (e.g., an activated Fc receptor) on the surface of an effector cell. Mutations in the Fc region of an antibody that decrease or increase the affinity of an antibody for an Fc receptor and techniques for introducing such mutations into the Fc receptor or fragment thereof are known to one of skill in the art. Examples of mutations in the Fc receptor of an antibody that can be made to alter the affinity of the antibody for an Fc receptor are described in, e.g., Smith P et al., (2012) PNAS 109: 6181-6186, U.S. Pat. No. 6,737,056, and International Publication Nos. WO 02/060919; WO 98/23289; and WO 97/34631, which are incorporated herein by reference. 
     In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions or deletions) are introduced into an IgG constant domain, or FcRn-binding fragment thereof (preferably an Fc or hinge-Fc domain fragment) to alter (e.g., decrease or increase) half-life of the antibody in vivo. See, e.g., International Publication Nos. WO 02/060919; WO 98/23289; and WO 97/34631; and U.S. Pat. Nos. 5,869,046, 6,121,022, 6,277,375 and 6,165,745 for examples of mutations that will alter (e.g., decrease or increase) the half-life of an antibody in vivo. 
     In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions or deletions) are introduced into an IgG constant domain, or FcRn-binding fragment thereof (preferably an Fc or hinge-Fc domain fragment) to decrease the half-life of the anti-transferrin receptor antibody in vivo. In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions or deletions) are introduced into an IgG constant domain, or FcRn-binding fragment thereof (preferably an Fc or hinge-Fc domain fragment) to increase the half-life of the antibody in vivo. In some embodiments, the antibodies can have one or more amino acid mutations (e.g., substitutions) in the second constant (CH2) domain (residues 231-340 of human IgG1) and/or (e.g., and) the third constant (CH3) domain (residues 341-447 of human IgG1), with numbering according to the EU index in Kabat (Kabat E A et al., (1991) supra). In some embodiments, the constant region of the IgG1 of an antibody described herein comprises a methionine (M) to tyrosine (Y) substitution in position 252, a serine (S) to threonine (T) substitution in position 254, and a threonine (T) to glutamic acid (E) substitution in position 256, numbered according to the EU index as in Kabat. See U.S. Pat. No. 7,658,921, which is incorporated herein by reference. This type of mutant IgG, referred to as “YTE mutant” has been shown to display fourfold increased half-life as compared to wild-type versions of the same antibody (see Dall&#39;Acqua W F et al., (2006) J Biol Chem 281: 23514-24). In some embodiments, an antibody comprises an IgG constant domain comprising one, two, three or more amino acid substitutions of amino acid residues at positions 251-257, 285-290, 308-314, 385-389, and 428-436, numbered according to the EU index as in Kabat. 
     In some embodiments, one, two or more amino acid substitutions are introduced into an IgG constant domain Fc region to alter the effector function(s) of the anti-transferrin receptor antibody. The effector ligand to which affinity is altered can be, for example, an Fc receptor or the C1 component of complement. This approach is described in further detail in U.S. Pat. Nos. 5,624,821 and 5,648,260. In some embodiments, the deletion or inactivation (through point mutations or other means) of a constant region domain can reduce Fc receptor binding of the circulating antibody thereby increasing tumor localization. See, e.g., U.S. Pat. Nos. 5,585,097 and 8,591,886 for a description of mutations that delete or inactivate the constant domain and thereby increase tumor localization. In some embodiments, one or more amino acid substitutions may be introduced into the Fc region of an antibody described herein to remove potential glycosylation sites on Fc region, which may reduce Fc receptor binding (see, e.g., Shields R L et al., (2001) J Biol Chem 276: 6591-604). 
     In some embodiments, one or more amino in the constant region of a muscle-targeting antibody described herein can be replaced with a different amino acid residue such that the antibody has altered C1q binding and/or (e.g., and) reduced or abolished complement dependent cytotoxicity (CDC). This approach is described in further detail in U.S. Pat. No. 6,194,551 (Idusogie et al). In some embodiments, one or more amino acid residues in the N-terminal region of the CH2 domain of an antibody described herein are altered to thereby alter the ability of the antibody to fix complement. This approach is described further in International Publication No. WO 94/29351. In some embodiments, the Fc region of an antibody described herein is modified to increase the ability of the antibody to mediate antibody dependent cellular cytotoxicity (ADCC) and/or (e.g., and) to increase the affinity of the antibody for an Fey receptor. This approach is described further in International Publication No. WO 00/42072. 
     In some embodiments, the heavy and/or (e.g., and) light chain variable domain(s) sequence(s) of the antibodies provided herein can be used to generate, for example, CDR-grafted, chimeric, humanized, or composite human antibodies or antigen-binding fragments, as described elsewhere herein. As understood by one of ordinary skill in the art, any variant, CDR-grafted, chimeric, humanized, or composite antibodies derived from any of the antibodies provided herein may be useful in the compositions and methods described herein and will maintain the ability to specifically bind transferrin receptor, such that the variant, CDR-grafted, chimeric, humanized, or composite antibody has at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or more binding to transferrin receptor relative to the original antibody from which it is derived. 
     In some embodiments, the antibodies provided herein comprise mutations that confer desirable properties to the antibodies. For example, to avoid potential complications due to Fab-arm exchange, which is known to occur with native IgG4 mAbs, the antibodies provided herein may comprise a stabilizing ‘Adair’ mutation (Angal S., et al., “A single amino acid substitution abolishes the heterogeneity of chimeric mouse/human (IgG4) antibody,” Mol Immunol 30, 105-108; 1993), where serine 228 (EU numbering; residue 241 Kabat numbering) is converted to proline resulting in an IgG1-like hinge sequence. Accordingly, any of the antibodies may include a stabilizing ‘Adair’ mutation. 
     As provided herein, antibodies of this disclosure may optionally comprise constant regions or parts thereof. For example, a VL domain may be attached at its C-terminal end to a light chain constant domain like Cκ or Cλ. Similarly, a VH domain or portion thereof may be attached to all or part of a heavy chain like IgA, IgD, IgE, IgG, and IgM, and any isotype subclass. Antibodies may include suitable constant regions (see, for example, Kabat et al., Sequences of Proteins of Immunological Interest, No. 91-3242, National Institutes of Health Publications, Bethesda, Md. (1991)). Therefore, antibodies within the scope of this may disclosure include VH and VL domains, or an antigen binding portion thereof, combined with any suitable constant regions. 
     ii. Muscle-Targeting Peptides 
     Some aspects of the disclosure provide muscle-targeting peptides as muscle-targeting agents. Short peptide sequences (e.g., peptide sequences of 5-20 amino acids in length) that bind to specific cell types have been described. For example, cell-targeting peptides have been described in Vines e., et al., A. “Cell-penetrating and cell-targeting peptides in drug delivery”  Biochim Biophys Acta  2008, 1786: 126-38; Jarver P., et al., “In vivo biodistribution and efficacy of peptide mediated delivery”  Trends Pharmacol Sci  2010; 31: 528-35; Samoylova T. I., et al., “Elucidation of muscle-binding peptides by phage display screening”  Muscle Nerve  1999; 22: 460-6; U.S. Pat. No. 6,329,501, issued on Dec. 11, 2001, entitled “METHODS AND COMPOSITIONS FOR TARGETING COMPOUNDS TO MUSCLE”; and Samoylov A. M., et al., “Recognition of cell-specific binding of phage display derived peptides using an acoustic wave sensor.”  Biomol Eng  2002; 18: 269-72; the entire contents of each of which are incorporated herein by reference. By designing peptides to interact with specific cell surface antigens (e.g., receptors), selectivity for a desired tissue, e.g., muscle, can be achieved. Skeletal muscle-targeting has been investigated and a range of molecular payloads are able to be delivered. These approaches may have high selectivity for muscle tissue without many of the practical disadvantages of a large antibody or viral particle. Accordingly, in some embodiments, the muscle-targeting agent is a muscle-targeting peptide that is from 4 to 50 amino acids in length. In some embodiments, the muscle-targeting peptide is 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 amino acids in length. Muscle-targeting peptides can be generated using any of several methods, such as phage display. 
     In some embodiments, a muscle-targeting peptide may bind to an internalizing cell surface receptor that is overexpressed or relatively highly expressed in muscle cells, e.g. a transferrin receptor, compared with certain other cells. In some embodiments, a muscle-targeting peptide may target, e.g., bind to, a transferrin receptor. In some embodiments, a peptide that targets a transferrin receptor may comprise a segment of a naturally occurring ligand, e.g., transferrin. In some embodiments, a peptide that targets a transferrin receptor is as described in U.S. Pat. No. 6,743,893, filed Nov. 30, 2000, “RECEPTOR-MEDIATED UPTAKE OF PEPTIDES THAT BIND THE HUMAN TRANSFERRIN RECEPTOR”. In some embodiments, a peptide that targets a transferrin receptor is as described in Kawamoto, M. et al, “A novel transferrin receptor-targeted hybrid peptide disintegrates cancer cell membrane to induce rapid killing of cancer cells.” BMC Cancer. 2011 Aug. 18; 11:359. In some embodiments, a peptide that targets a transferrin receptor is as described in U.S. Pat. No. 8,399,653, filed May 20, 2011, “TRANSFERRIN/TRANSFERRIN RECEPTOR-MEDIATED SIRNA DELIVERY”. 
     As discussed above, examples of muscle targeting peptides have been reported. For example, muscle-specific peptides were identified using phage display library presenting surface heptapeptides. As one example a peptide having the amino acid sequence ASSLNIA (SEQ ID NO: 718) bound to C2C12 murine myotubes in vitro, and bound to mouse muscle tissue in vivo. Accordingly, in some embodiments, the muscle-targeting agent comprises the amino acid sequence ASSLNIA (SEQ ID NO: 718). This peptide displayed improved specificity for binding to heart and skeletal muscle tissue after intravenous injection in mice with reduced binding to liver, kidney, and brain. Additional muscle-specific peptides have been identified using phage display. For example, a 12 amino acid peptide was identified by phage display library for muscle targeting in the context of treatment for DMD. See, Yoshida D., et al., “Targeting of salicylate to skin and muscle following topical injections in rats.”  Int J Pharm  2002; 231: 177-84; the entire contents of which are hereby incorporated by reference. Here, a 12 amino acid peptide having the sequence SKTFNTHPQSTP (SEQ ID NO: 719) was identified and this muscle-targeting peptide showed improved binding to C2C12 cells relative to the ASSLNIA (SEQ ID NO: 718) peptide. 
     An additional method for identifying peptides selective for muscle (e.g., skeletal muscle) over other cell types includes in vitro selection, which has been described in Ghosh D., et al., “Selection of muscle-binding peptides from context-specific peptide-presenting phage libraries for adenoviral vector targeting” J Virol 2005; 79: 13667-72; the entire contents of which are incorporated herein by reference. By pre-incubating a random 12-mer peptide phage display library with a mixture of non-muscle cell types, non-specific cell binders were selected out. Following rounds of selection the 12 amino acid peptide TARGEHKEEELI (SEQ ID NO: 720) appeared most frequently. Accordingly, in some embodiments, the muscle-targeting agent comprises the amino acid sequence TARGEHKEEELI (SEQ ID NO: 720). 
     A muscle-targeting agent may an amino acid-containing molecule or peptide. A muscle-targeting peptide may correspond to a sequence of a protein that preferentially binds to a protein receptor found in muscle cells. In some embodiments, a muscle-targeting peptide contains a high propensity of hydrophobic amino acids, e.g. valine, such that the peptide preferentially targets muscle cells. In some embodiments, a muscle-targeting peptide has not been previously characterized or disclosed. These peptides may be conceived of, produced, synthesized, and/or (e.g., and) derivatized using any of several methodologies, e.g. phage displayed peptide libraries, one-bead one-compound peptide libraries, or positional scanning synthetic peptide combinatorial libraries. Exemplary methodologies have been characterized in the art and are incorporated by reference (Gray, B. P. and Brown, K. C. “Combinatorial Peptide Libraries: Mining for Cell-Binding Peptides” Chem Rev. 2014, 114:2, 1020-1081.; Samoylova, T. I. and Smith, B. F. “Elucidation of muscle-binding peptides by phage display screening.” Muscle Nerve, 1999, 22:4. 460-6.). In some embodiments, a muscle-targeting peptide has been previously disclosed (see, e.g. Writer M. J. et al. “Targeted gene delivery to human airway epithelial cells with synthetic vectors incorporating novel targeting peptides selected by phage display.” J. Drug Targeting. 2004; 12:185; Cal, D. “BDNF-mediated enhancement of inflammation and injury in the aging heart.” Physiol Genomics. 2006, 24:3, 191-7.; Zhang, L. “Molecular profiling of heart endothelial cells.” Circulation, 2005, 112:11, 1601-11.; McGuire, M. J. et al. “In vitro selection of a peptide with high selectivity for cardiomyocytes in vivo.” J Mol Biol. 2004, 342:1, 171-82.). Exemplary muscle-targeting peptides comprise an amino acid sequence of the following group: CQAQGQLVC (SEQ ID NO: 721), CSERSMNFC (SEQ ID NO: 722), CPKTRRVPC (SEQ ID NO: 723), WLSEAGPVVTVRALRGTGSW (SEQ ID NO: 724), ASSLNIA (SEQ ID NO: 718), CMQHSMRVC (SEQ ID NO: 725), and DDTRHWG (SEQ ID NO: 726). In some embodiments, a muscle-targeting peptide may comprise about 2-25 amino acids, about 2-20 amino acids, about 2-15 amino acids, about 2-10 amino acids, or about 2-5 amino acids. Muscle-targeting peptides may comprise naturally-occurring amino acids, e.g. cysteine, alanine, or non-naturally-occurring or modified amino acids. Non-naturally occurring amino acids include β-amino acids, homo-amino acids, proline derivatives, 3-substituted alanine derivatives, linear core amino acids, N-methyl amino acids, and others known in the art. In some embodiments, a muscle-targeting peptide may be linear; in other embodiments, a muscle-targeting peptide may be cyclic, e.g. bicyclic (see, e.g. Silvana, M. G. et al. Mol. Therapy, 2018, 26:1, 132-147.). 
     iii. Muscle-Targeting Receptor Ligands 
     A muscle-targeting agent may be a ligand, e.g. a ligand that binds to a receptor protein. A muscle-targeting ligand may be a protein, e.g. transferrin, which binds to an internalizing cell surface receptor expressed by a muscle cell. Accordingly, in some embodiments, the muscle-targeting agent is transferrin, or a derivative thereof that binds to a transferrin receptor. A muscle-targeting ligand may alternatively be a small molecule, e.g. a lipophilic small molecule that preferentially targets muscle cells relative to other cell types. Exemplary lipophilic small molecules that may target muscle cells include compounds comprising cholesterol, cholesteryl, stearic acid, palmitic acid, oleic acid, oleyl, linolene, linoleic acid, myristic acid, sterols, dihydrotestosterone, testosterone derivatives, glycerine, alkyl chains, trityl groups, and alkoxy acids. 
     iv. Muscle-Targeting Aptamers 
     A muscle-targeting agent may be an aptamer, e.g. an RNA aptamer, which preferentially targets muscle cells relative to other cell types. In some embodiments, a muscle-targeting aptamer has not been previously characterized or disclosed. These aptamers may be conceived of, produced, synthesized, and/or (e.g., and) derivatized using any of several methodologies, e.g. Systematic Evolution of Ligands by Exponential Enrichment. Exemplary methodologies have been characterized in the art and are incorporated by reference (Yan, A. C. and Levy, M. “Aptamers and aptamer targeted delivery” RNA biology, 2009, 6:3, 316-20.; Germer, K. et al. “RNA aptamers and their therapeutic and diagnostic applications.” Int. J. Biochem. Mol. Biol. 2013; 4: 27-40.). In some embodiments, a muscle-targeting aptamer has been previously disclosed (see, e.g. Phillippou, S. et al. “Selection and Identification of Skeletal-Muscle-Targeted RNA Aptamers.” Mol Ther Nucleic Acids. 2018, 10:199-214.; Thiel, W. H. et al. “Smooth Muscle Cell-targeted RNA Aptamer Inhibits Neointimal Formation.” Mol Ther. 2016, 24:4, 779-87.). Exemplary muscle-targeting aptamers include the A01B RNA aptamer and RNA Apt 14. In some embodiments, an aptamer is a nucleic acid-based aptamer, an oligonucleotide aptamer or a peptide aptamer. In some embodiments, an aptamer may be about 5-15 kDa, about 5-10 kDa, about 10-15 kDa, about 1-5 Da, about 1-3 kDa, or smaller. 
     v. Other Muscle-Targeting Agents 
     One strategy for targeting a muscle cell (e.g., a skeletal muscle cell) is to use a substrate of a muscle transporter protein, such as a transporter protein expressed on the sarcolemma. In some embodiments, the muscle-targeting agent is a substrate of an influx transporter that is specific to muscle tissue. In some embodiments, the influx transporter is specific to skeletal muscle tissue. Two main classes of transporters are expressed on the skeletal muscle sarcolemma, (1) the adenosine triphosphate (ATP) binding cassette (ABC) superfamily, which facilitate efflux from skeletal muscle tissue and (2) the solute carrier (SLC) superfamily, which can facilitate the influx of substrates into skeletal muscle. In some embodiments, the muscle-targeting agent is a substrate that binds to an ABC superfamily or an SLC superfamily of transporters. In some embodiments, the substrate that binds to the ABC or SLC superfamily of transporters is a naturally-occurring substrate. In some embodiments, the substrate that binds to the ABC or SLC superfamily of transporters is a non-naturally occurring substrate, for example, a synthetic derivative thereof that binds to the ABC or SLC superfamily of transporters. 
     In some embodiments, the muscle-targeting agent is a substrate of an SLC superfamily of transporters. SLC transporters are either equilibrative or use proton or sodium ion gradients created across the membrane to drive transport of substrates. Exemplary SLC transporters that have high skeletal muscle expression include, without limitation, the SATT transporter (ASCT1; SLC1A4), GLUT4 transporter (SLC2A4), GLUT7 transporter (GLUT7; SLC2A7), ATRC2 transporter (CAT-2; SLC7A2), LAT3 transporter (KIAA0245; SLC7A6), PHT1 transporter (PTR4; SLC15A4), OATP-J transporter (OATP5A1; SLC21A15), OCT3 transporter (EMT; SLC22A3), OCTN2 transporter (FLJ46769; SLC22A5), ENT transporters (ENT1; SLC29A1 and ENT2; SLC29A2), PAT2 transporter (SLC36A2), and SAT2 transporter (KIAA1382; SLC38A2). These transporters can facilitate the influx of substrates into skeletal muscle, providing opportunities for muscle targeting. 
     In some embodiments, the muscle-targeting agent is a substrate of an equilibrative nucleoside transporter 2 (ENT2) transporter. Relative to other transporters, ENT2 has one of the highest mRNA expressions in skeletal muscle. While human ENT2 (hENT2) is expressed in most body organs such as brain, heart, placenta, thymus, pancreas, prostate, and kidney, it is especially abundant in skeletal muscle. Human ENT2 facilitates the uptake of its substrates depending on their concentration gradient. ENT2 plays a role in maintaining nucleoside homeostasis by transporting a wide range of purine and pyrimidine nucleobases. The hENT2 transporter has a low affinity for all nucleosides (adenosine, guanosine, uridine, thymidine, and cytidine) except for inosine. Accordingly, in some embodiments, the muscle-targeting agent is an ENT2 substrate. Exemplary ENT2 substrates include, without limitation, inosine, 2′,3′-dideoxyinosine, and calofarabine. In some embodiments, any of the muscle-targeting agents provided herein are associated with a molecular payload (e.g., oligonucleotide payload). In some embodiments, the muscle-targeting agent is covalently linked to the molecular payload. In some embodiments, the muscle-targeting agent is non-covalently linked to the molecular payload. 
     In some embodiments, the muscle-targeting agent is a substrate of an organic cation/carnitine transporter (OCTN2), which is a sodium ion-dependent, high affinity carnitine transporter. In some embodiments, the muscle-targeting agent is carnitine, mildronate, acetylcarnitine, or any derivative thereof that binds to OCTN2. In some embodiments, the carnitine, mildronate, acetylcarnitine, or derivative thereof is covalently linked to the molecular payload (e.g., oligonucleotide payload). 
     A muscle-targeting agent may be a protein that is protein that exists in at least one soluble form that targets muscle cells. In some embodiments, a muscle-targeting protein may be hemojuvelin (also known as repulsive guidance molecule C or hemochromatosis type 2 protein), a protein involved in iron overload and homeostasis. In some embodiments, hemojuvelin may be full length or a fragment, or a mutant with at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98% or at least 99% sequence identity to a functional hemojuvelin protein. In some embodiments, a hemojuvelin mutant may be a soluble fragment, may lack a N-terminal signaling, and/or (e.g., and) lack a C-terminal anchoring domain. In some embodiments, hemojuvelin may be annotated under GenBank RefSeq Accession Numbers NM_001316767.1, NM_145277.4, NM_202004.3, NM_213652.3, or NM_213653.3. It should be appreciated that a hemojuvelin may be of human, non-human primate, or rodent origin. 
     B. Molecular Payloads 
     Some aspects of the disclosure provide molecular payloads, e.g., for modulating a biological outcome, e.g., the transcription of a DNA sequence, the expression of a protein, or the activity of a protein. In some embodiments, a molecular payload is linked to, or otherwise associated with a muscle-targeting agent. In some embodiments, such molecular payloads are capable of targeting to a muscle cell, e.g., via specifically binding to a nucleic acid or protein in the muscle cell following delivery to the muscle cell by an associated muscle-targeting agent. It should be appreciated that various types of muscle-targeting agents may be used in accordance with the disclosure. For example, the molecular payload may comprise, or consist of, an oligonucleotide (e.g., antisense oligonucleotide), a peptide (e.g., a peptide that binds a nucleic acid or protein associated with disease in a muscle cell), a protein (e.g., a protein that binds a nucleic acid or protein associated with disease in a muscle cell), or a small molecule (e.g., a small molecule that modulates the function of a nucleic acid or protein associated with disease in a muscle cell). In some embodiments, the molecular payload is an oligonucleotide that comprises a strand having a region of complementarity to a DMPK allele comprising a disease-associated-repeat expansion. Exemplary molecular payloads are described in further detail herein, however, it should be appreciated that the exemplary molecular payloads provided herein are not meant to be limiting. 
     i. Oligonucleotides 
     Any suitable oligonucleotide may be used as a molecular payload, as described herein. In some embodiments, the oligonucleotide may be designed to cause degradation of an mRNA (e.g., the oligonucleotide may be a gapmer, an siRNA, a ribozyme or an aptamer that causes degradation). In some embodiments, the oligonucleotide may be designed to block translation of an mRNA (e.g., the oligonucleotide may be a mixmer, an siRNA or an aptamer that blocks translation). In some embodiments, an oligonucleotide may be designed to caused degradation and block translation of an mRNA. In some embodiments, an oligonucleotide may be a guide nucleic acid (e.g., guide RNA) for directing activity of an enzyme (e.g., a gene editing enzyme). Other examples of oligonucleotides are provided herein. It should be appreciated that, in some embodiments, oligonucleotides in one format (e.g., antisense oligonucleotides) may be suitably adapted to another format (e.g., siRNA oligonucleotides) by incorporating functional sequences (e.g., antisense strand sequences) from one format to the other format. 
     Examples of oligonucleotides useful for targeting DMPK are provided in US Patent Application Publication 20100016215A1, published on Jan. 1, 2010, entitled Compound And Method For Treating Myotonic Dystrophy; US Patent Application Publication 20130237585A1, published Jul. 19, 2010, Modulation Of Dystrophia Myotonica-Protein Kinase (DMPK) Expression; US Patent Application Publication 20150064181A1, published on Mar. 5, 2015, entitled “Antisense Conjugates For Decreasing Expression Of Dmpk”; US Patent Application Publication 20150238627A1, published on Aug. 27, 2015, entitled “Peptide-Linked Morpholino Antisense Oligonucleotides For Treatment Of Myotonic Dystrophy”; and US Patent Application Publication 20160304877A1, published on Oct. 20, 2016, entitled “Compounds And Methods For Modulation Of Dystrophia Myotonica-Protein Kinase (Dmpk) Expression,” the contents of each of which are incorporated herein in their entireties. 
     Examples of oligonucleotides for promoting DMPK gene editing include US Patent Application Publication 20170088819A1, published on Mar. 3, 2017, entitled “Genetic Correction Of Myotonic Dystrophy Type 1”; and International Patent Application Publication WO18002812A1, published on Apr. 1, 2018, entitled “Materials And Methods For Treatment Of Myotonic Dystrophy Type 1 (DM1) And Other Related Disorders,” the contents of each of which are incorporated herein in their entireties. 
     Further examples of complexes and molecular payloads (e.g., DMPK-targeting oligonucleotides) are provided in International Patent Application Publication WO2020/028861, published on Feb. 6, 2020, entitled, “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”; and International Patent Application Publication WO2020/028857, published on Feb. 6, 2020, entitled, “MUSCLE-TARGETING COMPLEXES AND USES THEREOF”, the contents of each of which are incorporated herein by reference. 
     In some embodiments, oligonucleotides may have a region of complementarity to a sequence set forth as follows, which is an example human DMPK gene sequence (Gene ID 1760; NM_001081560.2): 
     
       
         
           
               
            
               
                 (SEQ ID NO: 727) 
               
               
                 AGGGGGGCTGGACCAAGGGGTGGGGAGAAGGGGAGGAGGCCTCGGCCGG 
               
               
                   
               
               
                 CCGCAGAGAGAAGTGGCCAGAGAGGCCCAGGGGACAGCCAGGGACAGGC 
               
               
                   
               
               
                 AGACATGCAGCCAGGGCTCCAGGGCCTGGACAGGGGCTGCCAGGCCCTG 
               
               
                   
               
               
                 TGACAGGAGGACCCCGAGCCCCCGGCCCGGGGAGGGGCCATGGTGCTGC 
               
               
                   
               
               
                 CTGTCCAACATGTCAGCCGAGGTGCGGCTGAGGCGGCTCCAGCAGCTGG 
               
               
                   
               
               
                 TGTTGGACCCGGGCTTCCTGGGGCTGGAGCCCCTGCTCGACCTTCTCCT 
               
               
                   
               
               
                 GGGCGTCCACCAGGAGCTGGGCGCCTCCGAACTGGCCCAGGACAAGTAC 
               
               
                   
               
               
                 GTGGCCGACTTCTTGCAGTGGGCGGAGCCCATCGTGGTGAGGCTTAAGG 
               
               
                   
               
               
                 AGGTCCGACTGCAGAGGGACGACTTCGAGATTCTGAAGGTGATCGGACG 
               
               
                   
               
               
                 CGGGGCGTTCAGCGAGGTAGCGGTAGTGAAGATGAAGCAGACGGGCCAG 
               
               
                   
               
               
                 GTGTATGCCATGAAGATCATGAACAAGTGGGACATGCTGAAGAGGGGCG 
               
               
                   
               
               
                 AGGTGTCGTGCTTCCGTGAGGAGAGGGACGTGTTGGTGAATGGGGACCG 
               
               
                   
               
               
                 GCGGTGGATCACGCAGCTGCACTTCGCCTTCCAGGATGAGAACTACCTG 
               
               
                   
               
               
                 TACCTGGTCATGGAGTATTACGTGGGCGGGGACCTGCTGACACTGCTGA 
               
               
                   
               
               
                 GCAAGTTTGGGGAGCGGATTCCGGCCGAGATGGCGCGCTTCTACCTGGC 
               
               
                   
               
               
                 GGAGATTGTCATGGCCATAGACTCGGTGCACCGGCTTGGCTACGTGCAC 
               
               
                   
               
               
                 AGGGACATCAAACCCGACAACATCCTGCTGGACCGCTGTGGCCACATCC 
               
               
                   
               
               
                 GCCTGGCCGACTTCGGCTCTTGCCTCAAGCTGCGGGCAGATGGAACGGT 
               
               
                   
               
               
                 GCGGTCGCTGGTGGCTGTGGGCACCCCAGACTACCTGTCCCCCGAGATC 
               
               
                   
               
               
                 CTGCAGGCTGTGGGCGGTGGGCCTGGGACAGGCAGCTACGGGCCCGAGT 
               
               
                   
               
               
                 GTGACTGGTGGGCGCTGGGTGTATTCGCCTATGAAATGTTCTATGGGCA 
               
               
                   
               
               
                 GACGCCCTTCTACGCGGATTCCACGGCGGAGACCTATGGCAAGATCGTC 
               
               
                   
               
               
                 CACTACAAGGAGCACCTCTCTCTGCCGCTGGTGGACGAAGGGGTCCCTG 
               
               
                   
               
               
                 AGGAGGCTCGAGACTTCATTCAGCGGTTGCTGTGTCCCCCGGAGACACG 
               
               
                   
               
               
                 GCTGGGCCGGGGTGGAGCAGGCGACTTCCGGACACATCCCTTCTTCTTT 
               
               
                   
               
               
                 GGCCTCGACTGGGATGGTCTCCGGGACAGCGTGCCCCCCTTTACACCGG 
               
               
                   
               
               
                 ATTTCGAAGGTGCCACCGACACATGCAACTTCGACTTGGTGGAGGACGG 
               
               
                   
               
               
                 GCTCACTGCCATGGAGACACTGTCGGACATTCGGGAAGGTGCGCCGCTA 
               
               
                   
               
               
                 GGGGTCCACCTGCCTTTTGTGGGCTACTCCTACTCCTGCATGGCCCTCA 
               
               
                   
               
               
                 GGGACAGTGAGGTCCCAGGCCCCACACCCATGGAACTGGAGGCCGAGCA 
               
               
                   
               
               
                 GCTGCTTGAGCCACACGTGCAAGCGCCCAGCCTGGAGCCCTCGGTGTCC 
               
               
                   
               
               
                 CCACAGGATGAAACAGCTGAAGTGGCAGTTCCAGCGGCTGTCCCTGCGG 
               
               
                   
               
               
                 CAGAGGCTGAGGCCGAGGTGACGCTGCGGGAGCTCCAGGAAGCCCTGGA 
               
               
                   
               
               
                 GGAGGAGGTGCTCACCCGGCAGAGCCTGAGCCGGGAGATGGAGGCCATC 
               
               
                   
               
               
                 CGCACGGACAACCAGAACTTCGCCAGTCAACTACGCGAGGCAGAGGCTC 
               
               
                   
               
               
                 GGAACCGGGACCTAGAGGCACACGTCCGGCAGTTGCAGGAGCGGATGGA 
               
               
                   
               
               
                 GTTGCTGCAGGCAGAGGGAGCCACAGCTGTCACGGGGGTCCCCAGTCCC 
               
               
                   
               
               
                 CGGGCCACGGATCCACCTTCCCATCTAGATGGCCCCCCGGCCGTGGCTG 
               
               
                   
               
               
                 TGGGCCAGTGCCCGCTGGTGGGGCCAGGCCCCATGCACCGCCGCCACCT 
               
               
                   
               
               
                 GCTGCTCCCTGCCAGGGTCCCTAGGCCTGGCCTATCGGAGGCGCTTTCC 
               
               
                   
               
               
                 CTGCTCCTGTTCGCCGTTGTTCTGTCTCGTGCCGCCGCCCTGGGCTGCA 
               
               
                   
               
               
                 TTGGGTTGGTGGCCCACGCCGGCCAACTCACCGCAGTCTGGCGCCGCCC 
               
               
                   
               
               
                 AGGAGCCGCCCGCGCTCCCTGAACCCTAGAACTGTCTTCGACTCCGGGG 
               
               
                   
               
               
                 CCCCGTTGGAAGACTGAGTGCCCGGGGCACGGCACAGAAGCCGCGCCCA 
               
               
                   
               
               
                 CCGCCTGCCAGTTCACAACCGCTCCGAGCGTGGGTCTCCGCCCAGCTCC 
               
               
                   
               
               
                 AGTCCTGTGATCCGGGCCCGCCCCCTAGCGGCCGGGGAGGGAGGGGCCG 
               
               
                   
               
               
                 GGTCCGCGGCCGGCGAACGGGGCTCGAAGGGTCCTTGTAGCCGGGAATG 
               
               
                   
               
               
                 CTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGCTGC 
               
               
                   
               
               
                 TGCTGCTGCTGGGGGGATCACAGACCATTTCTTTCTTTCGGCCAGGCTG 
               
               
                   
               
               
                 AGGCCCTGACGTGGATGGGCAAACTGCAGGCCTGGGAAGGCAGCAAGCC 
               
               
                   
               
               
                 GGGCCGTCCGTGTTCCATCCTCCACGCACCCCCACCTATCGTTGGTTCG 
               
               
                   
               
               
                 CAAAGTGCAAAGCTTTCTTGTGCATGACGCCCTGCTCTGGGGAGCGTCT 
               
               
                   
               
               
                 GGCGCGATCTCTGCCTGCTTACTCGGGAAATTTGCTTTTGCCAAACCCG 
               
               
                   
               
               
                 CTTTTTCGGGGATCCCGCGCCCCCCTCCTCACTTGCGCTGCTCTCGGAG 
               
               
                   
               
               
                 CCCCAGCCGGCTCCGCCCGCTTCGGCGGTTTGGATATTTATTGACCTCG 
               
               
                   
               
               
                 TCCTCCGACTCGCTGACAGGCTACAGGACCCCCAACAACCCCAATCCAC 
               
               
                   
               
               
                 GTTTTGGATGCACTGAGACCCCGACATTCCTCGGTATTTATTGTCTGTC 
               
               
                   
               
               
                 CCCACCTAGGACCCCCACCCCCGACCCTCGCGAATAAAAGGCCCTCCAT 
               
               
                   
               
               
                 CTGCCCAAAGCTCTGGA. 
               
            
           
         
       
     
     In some embodiments, oligonucleotides may have a region of complementarity to a sequence set forth as follows, which is an example mouse DMPK gene sequence (Gene ID 13400; NM_001190490.1). 
                    (SEQ ID NO: 728)       GAACTGGCCAGAGAGACCCAAGGGATAGTCAGGGACGGGCAGACATGCA               GCTAGGGTTCTGGGGCCTGGACAGGGGCAGCCAGGCCCTGTGACGGGAA               GACCCCGAGCTCCGGCCCGGGGAGGGGCCATGGTGTTGCCTGCCCAACA               TGTCAGCCGAAGTGCGGCTGAGGCAGCTCCAGCAGCTGGTGCTGGACCC               AGGCTTCCTGGGACTGGAGCCCCTGCTCGACCTTCTCCTGGGCGTCCAC               CAGGAGCTGGGTGCCTCTCACCTAGCCCAGGACAAGTATGTGGCCGACT               TCTTGCAGTGGGTGGAGCCCATTGCAGCAAGGCTTAAGGAGGTCCGACT               GCAGAGGGATGATTTTGAGATTTTGAAGGTGATCGGGCGTGGGGCGTTC               AGCGAGGTAGCGGTGGTGAAGATGAAACAGACGGGCCAAGTGTATGCCA               TGAAGATTATGAATAAGTGGGACATGCTGAAGAGAGGCGAGGTGTCGTG               CTTCCGGGAAGAAAGGGATGTATTAGTGAAAGGGGACCGGCGCTGGATC               ACACAGCTGCACTTTGCCTTCCAGGATGAGAACTACCTGTACCTGGTCA               TGGAATACTACGTGGGCGGGGACCTGCTAACGCTGCTGAGCAAGTTTGG               GGAGCGGATCCCCGCCGAGATGGCTCGCTTCTACCTGGCCGAGATTGTC               ATGGCCATAGACTCCGTGCACCGGCTGGGCTACGTGCACAGGGACATCA               AACCAGATAACATTCTGCTGGACCGATGTGGGCACATTCGCCTGGCAGA               CTTCGGCTCCTGCCTCAAACTGCAGCCTGATGGAATGGTGAGGTCGCTG               GTGGCTGTGGGCACCCCGGACTACCTGTCTCCTGAGATTCTGCAGGCCG               TTGGTGGAGGGCCTGGGGCAGGCAGCTACGGGCCAGAGTGTGACTGGTG               GGCACTGGGCGTGTTCGCCTATGAGATGTTCTATGGGCAGACCCCCTTC               TACGCGGACTCCACAGCCGAGACATATGCCAAGATTGTGCACTACAGGG               AACACTTGTCGCTGCCGCTGGCAGACACAGTTGTCCCCGAGGAAGCTCA               GGACCTCATTCGTGGGCTGCTGTGTCCTGCTGAGATAAGGCTAGGTCGA               GGTGGGGCAGACTTCGAGGGTGCCACGGACACATGCAATTTCGATGTGG               TGGAGGACCGGCTCACTGCCATGGTGAGCGGGGGCGGGGAGACGCTGTC               AGACATGCAGGAAGACATGCCCCTTGGGGTGCGCCTGCCCTTCGTGGGC               TACTCCTACTGCTGCATGGCCTTCAGAGACAATCAGGTCCCGGACCCCA               CCCCTATGGAACTAGAGGCCCTGCAGTTGCCTGTGTCAGACTTGCAAGG               GCTTGACTTGCAGCCCCCAGTGTCCCCACCGGATCAAGTGGCTGAAGAG               GCTGACCTAGTGGCTGTCCCTGCCCCTGTGGCTGAGGCAGAGACCACGG               TAACGCTGCAGCAGCTCCAGGAAGCCCTGGAAGAAGAGGTTCTCACCCG               GCAGAGCCTGAGCCGCGAGCTGGAGGCCATCCGGACCGCCAACCAGAAC               TTCTCCAGCCAACTACAGGAGGCCGAGGTCCGAAACCGAGACCTGGAGG               CGCATGTTCGGCAGCTACAGGAACGGATGGAGATGCTGCAGGCCCCAGG               AGCCGCAGCCATCACGGGGGTCCCCAGTCCCCGGGCCACGGATCCACCT               TCCCATCTAGATGGCCCCCCGGCCGTGGCTGTGGGCCAGTGCCCGCTGG               TGGGGCCAGGCCCCATGCACCGCCGTCACCTGCTGCTCCCTGCCAGGAT               CCCTAGGCCTGGCCTATCCGAGGCGCGTTGCCTGCTCCTGTTCGCCGCT               GCTCTGGCTGCTGCCGCCACACTGGGCTGCACTGGGTTGGTGGCCTATA               CCGGCGGTCTCACCCCAGTCTGGTGTTTCCCGGGAGCCACCTTCGCCCC               CTGAACCCTAAGACTCCAAGCCATCTTTCATTTAGGCCTCCTAGGAAGG               TCGAGCGACCAGGGAGCGACCCAAAGCGTCTCTGTGCCCATCGCGCCCC               CCCCCCCCCCCCACCGCTCCGCTCCACACTTCTGTGAGCCTGGGTCCCC               ACCCAGCTCCGCTCCTGTGATCCAGGCCTGCCACCTGGCGGCCGGGGAG               GGAGGAACAGGGCTCGTGCCCAGCACCCCTGGTTCCTGCAGAGCTGGTA               GCCACCGCTGCTGCAGCAGCTGGGCATTCGCCGACCTTGCTTTACTCAG               CCCCGACGTGGATGGGCAAACTGCTCAGCTCATCCGATTTCACTTTTTC               ACTCTCCCAGCCATCAGTTACAAGCCATAAGCATGAGCCCCCTATTTCC               AGGGACATCCCATTCCCATAGTGATGGATCAGCAAGACCTCTGCCAGCA               CACACGGAGTCTTTGGCTTCGGACAGCCTCACTCCTGGGGGTTGCTGCA               ACTCCTTCCCCGTGTACACGTCTGCACTCTAACAACGGAGCCACAGCTG               CACTCCCCCCTCCCCCAAAGCAGTGTGGGTATTTATTGATCTTGTTATC               TGACTCACTGACAGACTCCGGGACCCACGTTTTAGATGCATTGAGACTC               GACATTCCTCGGTATTTATTGTCTGTCCCCACCTACGACCTCCACTCCC               GACCCTTGCGAATAAAATACTTCTGGTCTGCCCTAAA            
In some embodiments, an oligonucleotide may have a region of complementarity to DMPK gene sequences of multiple species, e.g., selected from human, mouse and non-human species.
 
     In some embodiments, the oligonucleotide may have region of complementarity to a mutant form of DMPK, for example, a mutant form as reported in Botta A. et al. “The CTG repeat expansion size correlates with the splicing defects observed in muscles from myotonic dystrophy type 1 patients.” J Med Genet. 2008 October; 45(10):639-46.; and Machuca-Tzili L. et al. “Clinical and molecular aspects of the myotonic dystrophies: a review.” Muscle Nerve. 2005 July; 32(1):1-18.; the contents of each of which are incorporated herein by reference in their entireties. 
     In some embodiments, the oligonucleotide may target lncRNA or mRNA, e.g., for degradation. In some embodiments, the oligonucleotide may target, e.g., for degradation, a nucleic acid encoding a protein involved in a mismatch repair pathway, e.g., MSH2, MutLalpha, MutSbeta, MutLalpha. Non-limiting examples of proteins involved in mismatch repair pathways, for which mRNAs encoding such proteins may be targeted by oligonucleotides described herein, are described in Iyer, R. R. et al., “ DNA triplet repeat expansion and mismatch repair ” Annu Rev Biochem. 2015; 84:199-226.; and Schmidt M. H. and Pearson C. E., “Disease-associated repeat instability and mismatch repair” DNA Repair (Amst). 2016 February; 38:117-26. 
     In some embodiments, an oligonucleotide provided herein is an antisense oligonucleotide targeting DMPK. In some embodiments, the oligonucleotide targeting is any one of the antisense oligonucleotides (e.g., a Gapmer) targeting DMPK as described in US Patent Application Publication US20160304877A1, published on Oct. 20, 2016, entitled “Compounds And Methods For Modulation Of Dystrophia Myotonica-Protein Kinase (DMPK) Expression,” incorporated herein by reference). In some embodiments, the DMPK targeting oligonucleotide targets a region of the DMPK gene sequence as set forth in Genbank accession No. NM_001081560.2 (SEQ ID NO: 727) or as set forth in Genbank accession No. NG_009784.1. 
     In some embodiments, the DMPK targeting oligonucleotide comprises a nucleotide sequence comprising a region complementary to a target region that is at least 10 continuous nucleotides (e.g., at least 10, at least 12, at least 14, at least 16, or more continuous nucleotides) in SEQ ID NO: 727. 
     In some embodiments, the DMPK targeting oligonucleotide comprise a gapmer motif. “Gapmer” means a chimeric antisense compound in which an internal region having a plurality of nucleotides that support RNase H cleavage is positioned between external regions having one or more nucleotides, wherein the nucleotides comprising the internal region are chemically distinct from the nucleotide or nucleotides comprising the external regions. The internal region can be referred to as a “gap segment” and the external regions can be referred to as “wing segments.” In some embodiments, the DMPK targeting oligonucleotide comprises one or more modified nucleotides, and/or (e.g., and) one or more modified internucleotide linkages. In some embodiments, the internucleotide linkage is a phosphorothioate linkage. In some embodiments, the oligonucleotide comprises a full phosphorothioate backbone. In some embodiments, the oligonucleotide is a DNA gapmer with cET ends (e.g., 3-10-3; cET-DNA-cET). In some embodiments, the DMPK targeting oligonucleotide comprises one or more 6′-(S)—CH 3  biocyclic nucleotides, one or more β-D-2′-deoxyribonucleotides, and/or (e.g., and) one or more 5-methylcytosine nucleotides. 
     In some embodiments, the DMPK targeting oligonucleotide is a gapmer having the formula 5′-X-Y-Z-3′, with X and Z as wing segments and Y as the gap segment. In some embodiments, the DMPK targeting oligonucleotide is a gapmer having a 5′-4-8-4-3′ formula. In some embodiments, the DMPK targeting oligonucleotide is a gapmer having a 5′-5-10-5-3′ formula. In some embodiments, the DMPK targeting oligonucleotide is a gapmer having a 5′-3-10-3-3′ formula. In some embodiments, the DMPK targeting oligonucleotide is a gapmer comprising one or more of 5-methylcytosine nucleotides, 2′OMe nucleotides, 2′fluoro nucleotides, LNAs, and/or (e.g., and) 2′-O-methoxyethyl (2′-MOE) nucleotides. In some embodiments, the DMPK targeting oligonucleotide is a gapmer comprising one or more modified internucleotide (e.g., a phosphorothioate linkage). In some embodiments, the DMPK targeting oligonucleotide is a gapmer comprising a full phosphorothioate backbone. In some embodiments, the DMPK targeting oligonucleotide is a gapmer comprising a mix of phosphorothioate linkages and phosphodiester linkages. 
     In some embodiments, the DMPK-targeting oligonucleotide is selected from the oligonucleotides listed in Table 10 and Table 16. In some embodiments, any one of the DMPK-targeting oligonucleotides can be in salt form, e.g., as sodium, potassium, or magnesium salts. 
     In some embodiments, the 5′ or 3′ nucleoside (e.g., terminal nucleoside) of any one of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table Table 10 and Table 16) is conjugated to an amine group, optionally via a spacer. In some embodiments, the spacer comprises an aliphatic moiety. In some embodiments, the spacer comprises a polyethylene glycol moiety. In some embodiments, a phosphodiester linkage is present between the spacer and the 5′ or 3′ nucleoside of the oligonucleotide. In some embodiments, the 5′ or 3′ nucleoside (e.g., terminal nucleoside) of any of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table 10 and Table 16) is conjugated to a spacer that is a substituted or unsubstituted aliphatic, substituted or unsubstituted heteroaliphatic, substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, —O—, —N(R A )—, —S—, —C(═O)—, —C(═O)O—, —C(═O)NR A —, —NR A C(═O)—, —NR A C(═O)R A —, —C(═O)R A —, —NR A C(═O)O—, —NR A C(═O)N(R A )—, —OC(═O)—, —OC(═O)O—, —OC(═O)N(R A )—, —S(O) 2 NR A —, —NR A S(O) 2 —, or a combination thereof; each R A  is independently hydrogen or substituted or unsubstituted alkyl. In certain embodiments, the spacer is a substituted or unsubstituted alkylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted heteroarylene, —O—, —N(R A )—, or —C(═O)N(R A ) 2 , or a combination thereof. 
     In some embodiments, the 5′ or 3′ nucleoside of any one of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table 10 and Table 16) is conjugated to a compound of the formula —NH 2 —(CH 2 ) n —, wherein n is an integer from 1 to 12. In some embodiments, n is 6, 7, 8, 9, 10, 11, or 12. In some embodiments, a phosphodiester linkage is present between the compound of the formula NH 2 —(CH 2 ) n — and the 5′ or 3′ nucleoside of the oligonucleotide. In some embodiments, a compound of the formula NH 2 —(CH 2 ) 6 — is conjugated to the oligonucleotide via a reaction between 6-amino-1-hexanol (NH 2 —(CH 2 ) 6 —OH) and the 5′ phosphate of the oligonucleotide. 
     In some embodiments, the oligonucleotide is conjugated to a targeting agent, e.g., a muscle targeting agent such as an anti-TfR antibody, e.g., via the amine group. 
     a. Oligonucleotide Size/Sequence 
     Oligonucleotides may be of a variety of different lengths, e.g., depending on the format. In some embodiments, an oligonucleotide is 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 75, or more nucleotides in length. In some embodiments, the oligonucleotide is 8 to 50 nucleotides in length, 8 to 40 nucleotides in length, 8 to 30 nucleotides in length, 10 to 15 nucleotides in length, 10 to 20 nucleotides in length, 15 to 25 nucleotides in length, 21 to 23 nucleotides in lengths, etc. 
     In some embodiments, a complementary nucleic acid sequence of an oligonucleotide for purposes of the present disclosure is specifically hybridizable or specific for the target nucleic acid when binding of the sequence to the target molecule (e.g., mRNA) interferes with the normal function of the target (e.g., mRNA) to cause a loss of activity (e.g., inhibiting translation) or expression (e.g., degrading a target mRNA) and there is a sufficient degree of complementarity to avoid non-specific binding of the sequence to non-target sequences under conditions in which avoidance of non-specific binding is desired, e.g., under physiological conditions in the case of in vivo assays or therapeutic treatment, and in the case of in vitro assays, under conditions in which the assays are performed under suitable conditions of stringency. Thus, in some embodiments, an oligonucleotide may be at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or 100% complementary to the consecutive nucleotides of an target nucleic acid. In some embodiments a complementary nucleotide sequence need not be 100% complementary to that of its target to be specifically hybridizable or specific for a target nucleic acid. 
     In some embodiments, an oligonucleotide comprises region of complementarity to a target nucleic acid that is in the range of 8 to 15, 8 to 30, 8 to 40, or 10 to 50, or 5 to 50, or 5 to 40 nucleotides in length. In some embodiments, a region of complementarity of an oligonucleotide to a target nucleic acid is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nucleotides in length. In some embodiments, the region of complementarity is complementary with at least 8 consecutive nucleotides of a target nucleic acid. In some embodiments, an oligonucleotide may contain 1, 2 or 3 base mismatches compared to the portion of the consecutive nucleotides of target nucleic acid. In some embodiments the oligonucleotide may have up to 3 mismatches over 15 bases, or up to 2 mismatches over 10 bases. 
     In some embodiments, an oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides of a sequence comprising any one of SEQ ID NO: 246-481 and 778-795. In some embodiments, an oligonucleotide comprises a sequence comprising any one of SEQ ID NO: 246-481 and 778-795. In some embodiments, an oligonucleotide comprises a sequence that shares at least 70%, 75%, 80%, 85%, 90%, 95%, or 97% sequence identity with at least 12 or at least 15 consecutive nucleotides of any one of SEQ ID NO: 246-481 and 778-795. 
     In some embodiments, an oligonucleotide comprises a sequence that targets a DMPK sequence comprising any one of SEQ ID NO: 482-717. In some embodiments, an oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleotides (e.g., consecutive nucleotides) that are complementary to a DMPK sequence comprising any one of SEQ ID NO: 482-717. In some embodiments, an oligonucleotide comprises a sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, or 97% complementary with at least 12 or at least 15 consecutive nucleotides of any one of SEQ ID NO: 482-717. 
     In some embodiments, an oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides of a sequence comprising any one of SEQ ID NOs: 796-2328. In some embodiments, an oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 796-2328. In some embodiments, an oligonucleotide comprises a sequence that shares at least 70%, 75%, 80%, 85%, 90%, 95%, or 97% sequence identity with at least 12 or at least 15 consecutive nucleotides of any one of SEQ ID NO: 796-2328. 
     In some embodiments, an oligonucleotide comprises a sequence that targets a DMPK sequence comprising any one of SEQ ID NO: 2329-3861. In some embodiments, an oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleotides (e.g., consecutive nucleotides) that are complementary to a DMPK sequence comprising any one of SEQ ID NO: 2329-3861. In some embodiments, an oligonucleotide comprises a sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, or 97% complementary with at least 12 or at least 15 consecutive nucleotides of any one of SEQ ID NO: 2329-3861. 
     In some embodiments, the oligonucleotide comprises a region of complementarity to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861. In some embodiments, the region of complementarity is at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 19 or at least 20 nucleotides in length. In some embodiments, the region of complementarity is 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleotides in length. In some embodiments, the region of complementarity is in the range of 8 to 20, 10 to 20 or 15 to 20 nucleotides in length. In some embodiments, the region of complementarity is fully complementarity with all or a portion of its target sequence. In some embodiments, the region of complementarity includes 1, 2, 3 or more mismatches. 
     In some embodiments, the oligonucleotide is complementary (e.g., at least 85% at least 90%, at least 95%, or 100%) to a target sequence of any one of the oligonucleotides provided herein (e.g., the oligonucleotides listed in Table 10 and Table 16). In some embodiments, such target sequence is 100% complementary to the oligonucleotide listed in Table 10 and Table 16. 
     In some embodiments, one or more of the thymine bases (T&#39;s) in any one of the oligonucleotides provided herein (e.g., the oligonucleotides listed in Table 10 and Table 16) may optionally be uracil bases (U&#39;s), and/or one or more of the the U&#39;s may optionally be T&#39;s. 
     b. Oligonucleotide Modifications: 
     The oligonucleotides described herein may be modified, e.g., comprise a modified sugar moiety, a modified internucleoside linkage, a modified nucleotide and/or (e.g., and) combinations thereof. In addition, in some embodiments, oligonucleotides may exhibit one or more of the following properties: do not mediate alternative splicing; are not immune stimulatory; are nuclease resistant; have improved cell uptake compared to unmodified oligonucleotides; are not toxic to cells or mammals; have improved endosomal exit internally in a cell; minimizes TLR stimulation; or avoid pattern recognition receptors. Any of the modified chemistries or formats of oligonucleotides described herein can be combined with each other. For example, one, two, three, four, five, or more different types of modifications can be included within the same oligonucleotide. 
     In some embodiments, certain nucleotide modifications may be used that make an oligonucleotide into which they are incorporated more resistant to nuclease digestion than the native oligodeoxynucleotide or oligoribonucleotide molecules; these modified oligonucleotides survive intact for a longer time than unmodified oligonucleotides. Specific examples of modified oligonucleotides include those comprising modified backbones, for example, modified internucleoside linkages such as phosphorothioates, phosphotriesters, methyl phosphonates, short chain alkyl or cycloalkyl intersugar linkages or short chain heteroatomic or heterocyclic intersugar linkages. Accordingly, oligonucleotides of the disclosure can be stabilized against nucleolytic degradation such as by the incorporation of a modification, e.g., a nucleotide modification. 
     In some embodiments, an oligonucleotide may be of up to 50 or up to 100 nucleotides in length in which 2 to 10, 2 to 15, 2 to 16, 2 to 17, 2 to 18, 2 to 19, 2 to 20, 2 to 25, 2 to 30, 2 to 40, 2 to 45, or more nucleotides of the oligonucleotide are modified nucleotides. The oligonucleotide may be of 8 to 30 nucleotides in length in which 2 to 10, 2 to 15, 2 to 16, 2 to 17, 2 to 18, 2 to 19, 2 to 20, 2 to 25, 2 to 30 nucleotides of the oligonucleotide are modified nucleotides. The oligonucleotide may be of 8 to 15 nucleotides in length in which 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9, 2 to 10, 2 to 11, 2 to 12, 2 to 13, 2 to 14 nucleotides of the oligonucleotide are modified nucleotides. Optionally, the oligonucleotides may have every nucleotide except 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nucleotides modified. Oligonucleotide modifications are described further herein. 
     c. Modified Nucleosides 
     In some embodiments, the oligonucleotide described herein comprises at least one nucleoside modified at the 2′ position of the sugar. In some embodiments, an oligonucleotide comprises at least one 2′-modified nucleoside. In some embodiments, all of the nucleosides in the oligonucleotide are 2′-modified nucleosides. 
     In some embodiments, the oligonucleotide described herein comprises one or more non-bicyclic 2′-modified nucleosides, e.g., 2′-deoxy, 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA) modified nucleoside. 
     In some embodiments, the oligonucleotide described herein comprises one or more 2′-4′ bicyclic nucleosides in which the ribose ring comprises a bridge moiety connecting two atoms in the ring, e.g., connecting the 2′-O atom to the 4′-C atom via a methylene (LNA) bridge, an ethylene (ENA) bridge, or a (S)-constrained ethyl (cEt) bridge. Examples of LNAs are described in International Patent Application Publication WO/2008/043753, published on Apr. 17, 2008, and entitled “RNA Antagonist Compounds For The Modulation Of PCSK9”, the contents of which are incorporated herein by reference in its entirety. Examples of ENAs are provided in International Patent Publication No. WO 2005/042777, published on May 12, 2005, and entitled “APP/ENA Antisense”; Morita et al., Nucleic Acid Res., Suppl 1:241-242, 2001; Surono et al., Hum. Gene Ther., 15:749-757, 2004; Koizumi, Curr. Opin. Mol. Ther., 8:144-149, 2006 and Horie et al., Nucleic Acids Symp. Ser (Oxf), 49:171-172, 2005; the disclosures of which are incorporated herein by reference in their entireties. Examples of cEt are provided in U.S. Pat. Nos. 7,101,993; 7,399,845 and 7,569,686, each of which is herein incorporated by reference in its entirety. 
     In some embodiments, the oligonucleotide comprises a modified nucleoside disclosed in one of the following United States Patent or Patent Application Publications: U.S. Pat. No. 7,399,845, issued on Jul. 15, 2008, and entitled “6-Modified Bicyclic Nucleic Acid Analogs”; U.S. Pat. No. 7,741,457, issued on Jun. 22, 2010, and entitled “6-Modified Bicyclic Nucleic Acid Analogs”; U.S. Pat. No. 8,022,193, issued on Sep. 20, 2011, and entitled “6-Modified Bicyclic Nucleic Acid Analogs”; U.S. Pat. No. 7,569,686, issued on Aug. 4, 2009, and entitled “Compounds And Methods For Synthesis Of Bicyclic Nucleic Acid Analogs”; U.S. Pat. No. 7,335,765, issued on Feb. 26, 2008, and entitled “Novel Nucleoside And Oligonucleotide Analogues”; U.S. Pat. No. 7,314,923, issued on Jan. 1, 2008, and entitled “Novel Nucleoside And Oligonucleotide Analogues”; U.S. Pat. No. 7,816,333, issued on Oct. 19, 2010, and entitled “Oligonucleotide Analogues And Methods Utilizing The Same” and US Publication Number 2011/0009471 now U.S. Pat. No. 8,957,201, issued on Feb. 17, 2015, and entitled “Oligonucleotide Analogues And Methods Utilizing The Same”, the entire contents of each of which are incorporated herein by reference for all purposes. 
     In some embodiments, the oligonucleotide comprises at least one modified nucleoside that results in an increase in Tm of the oligonucleotide in a range of 1° C., 2° C., 3° C., 4° C., or 5° C. compared with an oligonucleotide that does not have the at least one modified nucleoside. The oligonucleotide may have a plurality of modified nucleosides that result in a total increase in Tm of the oligonucleotide in a range of 2° C., 3° C., 4° C., 5° C., 6° C., 7° C., 8° C., 9° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C. or more compared with an oligonucleotide that does not have the modified nucleoside. 
     The oligonucleotide may comprise a mix of nucleosides of different kinds. For example, an oligonucleotide may comprise a mix of 2′-deoxyribonucleosides or ribonucleosides and 2′-fluoro modified nucleosides. An oligonucleotide may comprise a mix of deoxyribonucleosides or ribonucleosides and 2′-O-Me modified nucleosides. An oligonucleotide may comprise a mix of 2′-fluoro modified nucleosides and 2′-O-Me modified nucleosides. An oligonucleotide may comprise a mix of 2′-4′ bicyclic nucleosides and 2′-MOE, 2′-fluoro, or 2′-O-Me modified nucleosides. An oligonucleotide may comprise a mix of non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE, 2′-fluoro, or 2′-O-Me) and 2′-4′ bicyclic nucleosides (e.g., LNA, ENA, cEt). 
     The oligonucleotide may comprise alternating nucleosides of different kinds. For example, an oligonucleotide may comprise alternating 2′-deoxyribonucleosides or ribonucleosides and 2′-fluoro modified nucleosides. An oligonucleotide may comprise alternating deoxyribonucleosides or ribonucleosides and 2′-O-Me modified nucleosides. An oligonucleotide may comprise alternating 2′-fluoro modified nucleosides and 2′-O-Me modified nucleosides. An oligonucleotide may comprise alternating 2′-4′ bicyclic nucleosides and 2′-MOE, 2′-fluoro, or 2′-O-Me modified nucleosides. An oligonucleotide may comprise alternating non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE, 2′-fluoro, or 2′-O-Me) and 2′-4′ bicyclic nucleosides (e.g., LNA, ENA, cEt). 
     In some embodiments, an oligonucleotide described herein comprises a 5′-vinylphosphonate modification, one or more abasic residues, and/or one or more inverted abasic residues. 
     d. Internucleoside Linkages/Backbones 
     In some embodiments, oligonucleotide may contain a phosphorothioate or other modified internucleoside linkage. In some embodiments, the oligonucleotide comprises phosphorothioate internucleoside linkages. In some embodiments, the oligonucleotide comprises phosphorothioate internucleoside linkages between at least two nucleotides. In some embodiments, the oligonucleotide comprises phosphorothioate internucleoside linkages between all nucleotides. For example, in some embodiments, oligonucleotides comprise modified internucleoside linkages at the first, second, and/or (e.g., and) third internucleoside linkage at the 5′ or 3′ end of the nucleotide sequence. 
     Phosphorus-containing linkages that may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates comprising 3′alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates comprising 3′-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs of these, and those having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′; see U.S. Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,196; 5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131; 5,399,676; 5,405,939; 5,453,496; 5,455, 233; 5,466,677; 5,476,925; 5,519,126; 5,536,821; 5,541,306; 5,550,111; 5,563, 253; 5,571,799; 5,587,361; and 5,625,050. 
     In some embodiments, oligonucleotides may have heteroatom backbones, such as methylene(methylimino) or MMI backbones; amide backbones (see De Mesmaeker et al. Ace. Chem. Res. 1995, 28:366-374); morpholino backbones (see Summerton and Weller, U.S. Pat. No. 5,034,506); or peptide nucleic acid (PNA) backbones (wherein the phosphodiester backbone of the oligonucleotide is replaced with a polyamide backbone, the nucleotides being bound directly or indirectly to the aza nitrogen atoms of the polyamide backbone, see Nielsen et al., Science 1991, 254, 1497). 
     e. Stereospecific Oligonucleotides 
     In some embodiments, internucleotidic phosphorus atoms of oligonucleotides are chiral, and the properties of the oligonucleotides by adjusted based on the configuration of the chiral phosphorus atoms. In some embodiments, appropriate methods may be used to synthesize P-chiral oligonucleotide analogs in a stereocontrolled manner (e.g., as described in Oka N, Wada T, Stereocontrolled synthesis of oligonucleotide analogs containing chiral internucleotidic phosphorus atoms. Chem Soc Rev. 2011 December; 40(12):5829-43.) In some embodiments, phosphorothioate containing oligonucleotides comprise nucleoside units that are joined together by either substantially all Sp or substantially all Rp phosphorothioate intersugar linkages are provided. In some embodiments, such phosphorothioate oligonucleotides having substantially chirally pure intersugar linkages are prepared by enzymatic or chemical synthesis, as described, for example, in U.S. Pat. No. 5,587,261, issued on Dec. 12, 1996, the contents of which are incorporated herein by reference in their entirety. In some embodiments, chirally controlled oligonucleotides provide selective cleavage patterns of a target nucleic acid. For example, in some embodiments, a chirally controlled oligonucleotide provides single site cleavage within a complementary sequence of a nucleic acid, as described, for example, in US Patent Application Publication 20170037399 Al, published on Feb. 2, 2017, entitled “CHIRAL DESIGN”, the contents of which are incorporated herein by reference in their entirety. 
     f. Morpholinos 
     In some embodiments, the oligonucleotide may be a morpholino-based compounds. Morpholino-based oligomeric compounds are described in Dwaine A. Braasch and David R. Corey, Biochemistry, 2002, 41(14), 4503-4510); Genesis, volume 30, issue 3, 2001; Heasman, J., Dev. Biol., 2002, 243, 209-214; Nasevicius et al., Nat. Genet., 2000, 26, 216-220; Lacerra et al., Proc. Natl. Acad. Sci., 2000, 97, 9591-9596; and U.S. Pat. No. 5,034,506, issued Jul. 23, 1991. In some embodiments, the morpholino-based oligomeric compound is a phosphorodiamidate morpholino oligomer (PMO) (e.g., as described in Iverson, Curr. Opin. Mol. Ther., 3:235-238, 2001; and Wang et al., J. Gene Med., 12:354-364, 2010; the disclosures of which are incorporated herein by reference in their entireties). 
     g. Peptide Nucleic Acids (PNAs) 
     In some embodiments, both a sugar and an internucleoside linkage (the backbone) of the nucleotide units of an oligonucleotide are replaced with novel groups. In some embodiments, the base units are maintained for hybridization with an appropriate nucleic acid target compound. One such oligomeric compound, an oligonucleotide mimetic that has been shown to have excellent hybridization properties, is referred to as a peptide nucleic acid (PNA). In PNA compounds, the sugar-backbone of an oligonucleotide is replaced with an amide containing backbone, for example, an aminoethylglycine backbone. The nucleobases are retained and are bound directly or indirectly to aza nitrogen atoms of the amide portion of the backbone. Representative publication that report the preparation of PNA compounds include, but are not limited to, U.S. Pat. Nos. 5,539,082; 5,714,331; and 5,719,262, each of which is herein incorporated by reference. Further teaching of PNA compounds can be found in Nielsen et al., Science, 1991, 254, 1497-1500. 
     h. Gapmers 
     In some embodiments, an oligonucleotide described herein is a gapmer. A gapmer oligonucleotide generally has the formula 5′-X-Y-Z-3′, with X and Z as flanking regions around a gap region Y. In some embodiments, flanking region X of formula 5′-X-Y-Z-3′ is also referred to as X region, flanking sequence X, 5′ wing region X, or 5′ wing segment. In some embodiments, flanking region Z of formula 5′-X-Y-Z-3′ is also referred to as Z region, flanking sequence Z, 3′ wing region Z, or 3′ wing segment. In some embodiments, gap region Y of formula 5′-X-Y-Z-3′ is also referred to as Y region, Y segment, or gap-segment Y. In some embodiments, each nucleoside in the gap region Y is a 2′-deoxyribonucleoside, and neither the 5′ wing region X or the 3′ wing region Z contains any 2′-deoxyribonucleosides. 
     In some embodiments, the Y region is a contiguous stretch of nucleotides, e.g., a region of 6 or more DNA nucleotides, which are capable of recruiting an RNAse, such as RNAse H. In some embodiments, the gapmer binds to the target nucleic acid, at which point an RNAse is recruited and can then cleave the target nucleic acid. In some embodiments, the Y region is flanked both 5′ and 3′ by regions X and Z comprising high-affinity modified nucleosides, e.g., one to six high-affinity modified nucleosides. Examples of high affinity modified nucleosides include, but are not limited to, 2′-modified nucleosides (e.g., 2′-MOE, 2′O-Me, 2′-F) or 2′-4′ bicyclic nucleosides (e.g., LNA, cEt, ENA). In some embodiments, the flanking sequences X and Z may be of 1-20 nucleotides, 1-8 nucleotides, or 1-5 nucleotides in length. The flanking sequences X and Z may be of similar length or of dissimilar lengths. In some embodiments, the gap-segment Y may be a nucleotide sequence of 5-20 nucleotides, 5-15 twelve nucleotides, or 6-10 nucleotides in length. 
     In some embodiments, the gap region of the gapmer oligonucleotides may contain modified nucleotides known to be acceptable for efficient RNase H action in addition to DNA nucleotides, such as C4′-substituted nucleotides, acyclic nucleotides, and arabino-configured nucleotides. In some embodiments, the gap region comprises one or more unmodified internucleosides. In some embodiments, one or both flanking regions each independently comprise one or more phosphorothioate internucleoside linkages (e.g., phosphorothioate internucleoside linkages or other linkages) between at least two, at least three, at least four, at least five or more nucleotides. In some embodiments, the gap region and two flanking regions each independently comprise modified internucleoside linkages (e.g., phosphorothioate internucleoside linkages or other linkages) between at least two, at least three, at least four, at least five or more nucleotides. 
     A gapmer may be produced using appropriate methods. Representative U.S. patents, U.S. patent publications, and PCT publications that teach the preparation of gapmers include, but are not limited to, U.S. Pat. Nos. 5,013,830; 5,149,797; 5,220,007; 5,256,775; 5,366,878; 5,403,711; 5,491,133; 5,565,350; 5,623,065; 5,652,355; 5,652,356; 5,700,922; 5,898,031; 7,015,315; 7,101,993; 7,399,845; 7,432,250; 7,569,686; 7,683,036; 7,750,131; 8,580,756; 9,045,754; 9,428,534; 9,695,418; 10,017,764; 10,260,069; 9,428,534; 8,580,756; U.S. patent publication Nos. US20050074801, US20090221685; US20090286969, US20100197762, and US20110112170; PCT publication Nos. WO2004069991; WO2005023825; WO2008049085 and WO2009090182; and EP Patent No. EP2,149,605, each of which is herein incorporated by reference in its entirety. 
     In some embodiments, a gapmer is 10-40 nucleosides in length. For example, a gapmer may be 10-40, 10-35, 10-30, 10-25, 10-20, 10-15, 15-40, 15-35, 15-30, 15-25, 15-20, 20-40, 20-35, 20-30, 20-25, 25-40, 25-35, 25-30, 30-40, 30-35, or 35-40 nucleosides in length. In some embodiments, a gapmer is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 nucleosides in length. 
     In some embodiments, the gap region Y in a gapmer is 5-20 nucleosides in length. For example, the gap region Y may be 5-20, 5-15, 5-10, 10-20, 10-15, or 15-20 nucleosides in length. In some embodiments, the gap region Y is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleosides in length. In some embodiments, each nucleoside in the gap region Y is a 2′-deoxyribonucleoside. In some embodiments, all nucleosides in the gap region Y are 2′-deoxyribonucleosides. In some embodiments, one or more of the nucleosides in the gap region Y is a modified nucleoside (e.g., a 2′ modified nucleoside such as those described herein). In some embodiments, one or more cytosines in the gap region Y are optionally 5-methyl-cytosines. In some embodiments, each cytosine in the gap region Y is a 5-methyl-cytosines. 
     In some embodiments, the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of a gapmer (Z in the 5′-X-Y-Z-3′ formula) are independently 1-20 nucleosides long. For example, the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) may be independently 1-20, 1-15, 1-10, 1-7, 1-5, 1-3, 1-2, 2-5, 2-7, 3-5, 3-7, 5-20, 5-15, 5-10, 10-20, 10-15, or 15-20 nucleosides long. In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) are independently 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleosides long. In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) are of the same length. In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) are of different lengths. In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) is longer than the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula). In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) is shorter than the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula). 
     In some embodiments, a gapmer comprises a 5′-X-Y-Z-3′ of 5-10-5, 4-12-4, 3-14-3, 2-16-2, 1-18-1, 3-10-3, 2-10-2, 1-10-1, 2-8-2, 4-6-4, 3-6-3, 2-6-2, 4-7-4, 3-7-3, 2-7-2, 4-8-4, 3-8-3, 2-8-2, 1-8-1, 2-9-2, 1-9-1, 2-10-2, 1-10-1, 1-12-1, 1-16-1, 2-15-1, 1-15-2, 1-14-3, 3-14-1, 2-14-2, 1-13-4, 4-13-1, 2-13-3, 3-13-2, 1-12-5, 5-12-1, 2-12-4, 4-12-2, 3-12-3, 1-11-6, 6-11-1, 2-11-5, 5-11-2, 3-11-4, 4-11-3, 1-17-1, 2-16-1, 1-16-2, 1-15-3, 3-15-1, 2-15-2, 1-14-4, 4-14-1, 2-14-3, 3-14-2, 1-13-5, 5-13-1, 2-13-4, 4-13-2, 3-13-3, 1-12-6, 6-12-1, 2-12-5, 5-12-2, 3-12-4, 4-12-3, 1-11-7, 7-11-1, 2-11-6, 6-11-2, 3-11-5, 5-11-3, 4-11-4, 1-18-1, 1-17-2, 2-17-1, 1-16-3, 1-16-3, 2-16-2, 1-15-4, 4-15-1, 2-15-3, 3-15-2, 1-14-5, 5-14-1, 2-14-4, 4-14-2, 3-14-3, 1-13-6, 6-13-1, 2-13-5, 5-13-2, 3-13-4, 4-13-3, 1-12-7, 7-12-1, 2-12-6, 6-12-2, 3-12-5, 5-12-3, 1-11-8, 8-11-1, 2-11-7, 7-11-2, 3-11-6, 6-11-3, 4-11-5, 5-11-4, 1-18-1, 1-17-2, 2-17-1, 1-16-3, 3-16-1, 2-16-2, 1-15-4, 4-15-1, 2-15-3, 3-15-2, 1-14-5, 2-14-4, 4-14-2, 3-14-3, 1-13-6, 6-13-1, 2-13-5, 5-13-2, 3-13-4, 4-13-3, 1-12-7, 7-12-1, 2-12-6, 6-12-2, 3-12-5, 5-12-3, 1-11-8, 8-11-1, 2-11-7, 7-11-2, 3-11-6, 6-11-3, 4-11-5, 5-11-4, 1-19-1, 1-18-2, 2-18-1, 1-17-3, 3-17-1, 2-17-2, 1-16-4, 4-16-1, 2-16-3, 3-16-2, 1-15-5, 2-15-4, 4-15-2, 3-15-3, 1-14-6, 6-14-1, 2-14-5, 5-14-2, 3-14-4, 4-14-3, 1-13-7, 7-13-1, 2-13-6, 6-13-2, 3-13-5, 5-13-3, 4-13-4, 1-12-8, 8-12-1, 2-12-7, 7-12-2, 3-12-6, 6-12-3, 4-12-5, 5-12-4, 2-11-8, 8-11-2, 3-11-7, 7-11-3, 4-11-6, 6-11-4, 5-11-5, 1-20-1, 1-19-2, 2-19-1, 1-18-3, 3-18-1, 2-18-2, 1-17-4, 4-17-1, 2-17-3, 3-17-2, 1-16-5, 2-16-4, 4-16-2, 3-16-3, 1-15-6, 6-15-1, 2-15-5, 5-15-2, 3-15-4, 4-15-3, 1-14-7, 7-14-1, 2-14-6, 6-14-2, 3-14-5, 5-14-3, 4-14-4, 1-13-8, 8-13-1, 2-13-7, 7-13-2, 3-13-6, 6-13-3, 4-13-5, 5-13-4, 2-12-8, 8-12-2, 3-12-7, 7-12-3, 4-12-6, 6-12-4, 5-12-5, 3-11-8, 8-11-3, 4-11-7, 7-11-4, 5-11-6, 6-11-5, 1-21-1, 1-20-2, 2-20-1, 1-20-3, 3-19-1, 2-19-2, 1-18-4, 4-18-1, 2-18-3, 3-18-2, 1-17-5, 2-17-4, 4-17-2, 3-17-3, 1-16-6, 6-16-1, 2-16-5, 5-16-2, 3-16-4, 4-16-3, 1-15-7, 7-15-1, 2-15-6, 6-15-2, 3-15-5, 5-15-3, 4-15-4, 1-14-8, 8-14-1, 2-14-7, 7-14-2, 3-14-6, 6-14-3, 4-14-5, 5-14-4, 2-13-8, 8-13-2, 3-13-7, 7-13-3, 4-13-6, 6-13-4, 5-13-5, 1-12-10, 10-12-1, 2-12-9, 9-12-2, 3-12-8, 8-12- 3, 4-12-7, 7-12-4, 5-12-6, 6-12-5, 4-11-8, 8-11-4, 5-11-7, 7-11-5, 6-11-6, 1-22-1, 1-21-2, 2-21-1, 1-21-3, 3-20-1, 2-20-2, 1-19-4, 4-19-1, 2-19-3, 3-19-2, 1-18-5, 2-18-4, 4-18-2, 3-18-3, 1-17-6, 6-17-1, 2-17-5, 5-17-2, 3-17-4, 4-17-3, 1-16-7, 7-16-1, 2-16-6, 6-16-2, 3-16-5, 5-16-3, 4-16-4, 1-15-8, 8-15-1, 2-15-7, 7-15-2, 3-15-6, 6-15-3, 4-15-5, 5-15-4, 2-14-8, 8-14-2, 3-14-7, 7-14-3, 4-14-6, 6-14-4, 5-14-5, 3-13-8, 8-13-3, 4-13-7, 7-13-4, 5-13-6, 6-13-5, 4-12-8, 8-12-4, 5-12-7, 7-12-5, 6-12-6, 5-11-8, 8-11-5, 6-11-7, or 7-11-6. The numbers indicate the number of nucleosides in X, Y, and Z regions in the 5′-X-Y-Z-3′ gapmer. 
     In some embodiments, one or more nucleosides in the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) or the 3′wing region of a gapmer (Z in the 5′-X-Y-Z-3′ formula) are modified nucleotides (e.g., high-affinity modified nucleosides). In some embodiments, the modified nucleoside (e.g., high-affinity modified nucleosides) is a 2′-modified nucleoside. In some embodiments, the 2′-modified nucleoside is a 2′-4′ bicyclic nucleoside or a non-bicyclic 2′-modified nucleoside. In some embodiments, the high-affinity modified nucleoside is a 2′-4′ bicyclic nucleoside (e.g., LNA, cEt, or ENA) or a non-bicyclic 2′-modified nucleoside (e.g., 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA)). 
     In some embodiments, one or more nucleosides in the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) are high-affinity modified nucleosides. In some embodiments, each nucleoside in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) is a high-affinity modified nucleoside. In some embodiments, one or more nucleosides in the 3′wing region of a gapmer (Z in the 5′-X-Y-Z-3′ formula) are high-affinity modified nucleosides. In some embodiments, each nucleoside in the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) is a high-affinity modified nucleoside. In some embodiments, one or more nucleosides in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) are high-affinity modified nucleosides and one or more nucleosides in the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) are high-affinity modified nucleosides. In some embodiments, each nucleoside in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) is a high-affinity modified nucleoside and each nucleoside in the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) is high-affinity modified nucleoside. 
     In some embodiments, the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) comprises the same high affinity nucleosides as the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula). For example, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) may comprise one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me). In another example, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) may comprise one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, each nucleoside in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) is a non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me). In some embodiments, each nucleoside in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) is a 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). 
     In some embodiments, a gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 1-7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein each nucleoside in X and Z is a non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and each nucleoside in Y is a 2′-deoxyribonucleoside. In some embodiments, the gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 1-7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein each nucleoside in X and Z is a 2′-4′ bicyclic nucleosides (e.g., LNA or cEt) and each nucleoside in Y is a 2′-deoxyribonucleoside. In some embodiments, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) comprises different high affinity nucleosides as the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula). For example, the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) may comprise one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) may comprise one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). In another example, the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) may comprise one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) may comprise one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). 
     In some embodiments, a gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 1-7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein each nucleoside in X is a non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me), each nucleoside in Z is a 2′-4′ bicyclic nucleosides (e.g., LNA or cEt), and each nucleoside in Y is a 2′-deoxyribonucleoside. In some embodiments, the gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 1-7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein each nucleoside in X is a 2′-4′ bicyclic nucleosides (e.g., LNA or cEt), each nucleoside in Z is a non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and each nucleoside in Y is a 2′-deoxyribonucleoside. 
     In some embodiments, the 5′wing region of a gapmer (X in the 5′-X-Y-Z-3′ formula) comprises one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′ Me) and one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) comprises one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, both the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) comprise one or more non-bicyclic 2′-modified nucleosides (e.g., 2′-MOE or 2′-O-Me) and one or more 2′-4′ bicyclic nucleosides (e.g., LNA or cEt). 
     In some embodiments, a gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein at least one but not all (e.g., 1, 2, 3, 4, 5, or 6) of positions 1, 2, 3, 4, 5, 6, or 7 in X (the 5′ most position is position 1) is a non-bicyclic 2′-modified nucleoside (e.g., 2′-MOE or 2′-O-Me), wherein the rest of the nucleosides in both X and Z are 2′-4′ bicyclic nucleosides (e.g., LNA or cEt), and wherein each nucleoside in Y is a 2′deoxyribonucleoside. In some embodiments, the gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein at least one but not all (e.g., 1, 2, 3, 4, 5, or 6) of positions 1, 2, 3, 4, 5, 6, or 7 in Z (the 5′ most position is position 1) is a non-bicyclic 2′-modified nucleoside (e.g., 2′-MOE or 2′-O-Me), wherein the rest of the nucleosides in both X and Z are 2′-4′ bicyclic nucleosides (e.g., LNA or cEt), and wherein each nucleoside in Y is a 2′deoxyribonucleoside. In some embodiments, the gapmer comprises a 5′-X-Y-Z-3′ configuration, wherein X and Z is independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length and Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, wherein at least one but not all (e.g., 1, 2, 3, 4, 5, or 6) of positions 1, 2, 3, 4, 5, 6, or 7 in X and at least one of positions but not all (e.g., 1, 2, 3, 4, 5, or 6) 1, 2, 3, 4, 5, 6, or 7 in Z (the 5′ most position is position 1) is a non-bicyclic 2′-modified nucleoside (e.g., 2′-MOE or 2′-O-Me), wherein the rest of the nucleosides in both X and Z are 2′-4′ bicyclic nucleosides (e.g., LNA or cEt), and wherein each nucleoside in Y is a 2′deoxyribonucleoside. 
     Non-limiting examples of gapmers configurations with a mix of non-bicyclic 2′-modified nucleoside (e.g., 2′-MOE or 2′-O-Me) and 2′-4′ bicyclic nucleosides (e.g., LNA or cEt) in the 5′wing region of the gapmer (X in the 5′-X-Y-Z-3′ formula) and/or the 3′wing region of the gapmer (Z in the 5′-X-Y-Z-3′ formula) include: BBB-(D)n-BBBAA; KKK-(D)n-KKKAA; LLL-(D)n-LLLAA; BBB-(D)n-BBBEE; KKK-(D)n-KKKEE; LLL-(D)n-LLLEE; BBB-(D)n-BBBAA; KKK-(D)n-KKKAA; LLL-(D)n-LLLAA; BBB-(D)n-BBBEE; KKK-(D)n-KKKEE; LLL-(D)n-LLLEE; BBB-(D)n-BBBAAA; KKK-(D)n-KKKAAA; LLL-(D)n-LLLAAA; BBB-(D)n-BBBEEE; KKK-(D)n-KKKEEE; LLL-(D)n-LLLEEE; BBB-(D)n-BBBAAA; KKK-(D)n-KKKAAA; LLL-(D)n-LLLAAA; BBB-(D)n-BBBEEE; KKK-(D)n-KKKEEE; LLL-(D)n-LLLEEE; BABA-(D)n-ABAB; KAKA-(D)n-AKAK; LALA-(D)n-ALAL; BEBE-(D)n-EBEB; KEKE-(D)n-EKEK; LELE-(D)n-ELEL; BABA-(D)n-ABAB; KAKA-(D)n-AKAK; LALA-(D)n-ALAL; BEBE-(D)n-EBEB; KEKE-(D)n-EKEK; LELE-(D)n-ELEL; ABAB-(D)n-ABAB; AKAK-(D)n-AKAK; ALAL-(D)n-ALAL; EBEB-(D)n-EBEB; EKEK-(D)n-EKEK; ELEL-(D)n-ELEL; ABAB-(D)n-ABAB; AKAK-(D)n-AKAK; ALAL-(D)n-ALAL; EBEB-(D)n-EBEB; EKEK-(D)n-EKEK; ELEL-(D)n-ELEL; AABB-(D)n-BBAA; BBAA-(D)n-AABB; AAKK-(D)n-KKAA; AALL-(D)n-LLAA; EEBB-(D)n-BBEE; EEKK-(D)n-KKEE; EELL-(D)n-LLEE; AABB-(D)n-BBAA; AAKK-(D)n-KKAA; AALL-(D)n-LLAA; EEBB-(D)n-BBEE; EEKK-(D)n-KKEE; EELL-(D)n-LLEE; BBB-(D)n-BBA; KKK-(D)n-KKA; LLL-(D)n-LLA; BBB-(D)n-BBE; KKK-(D)n-KKE; LLL-(D)n-LLE; BBB-(D)n-BBA; KKK-(D)n-KKA; LLL-(D)n-LLA; BBB-(D)n-BBE; KKK-(D)n-KKE; LLL-(D)n-LLE; BBB-(D)n-BBA; KKK-(D)n-KKA; LLL-(D)n-LLA; BBB-(D)n-BBE; KKK-(D)n-KKE; LLL-(D)n-LLE; ABBB-(D)n-BBBA; AKKK-(D)n-KKKA; ALLL-(D)n-LLLA; EBBB-(D)n-BBBE; EKKK-(D)n-KKKE; ELLL-(D)n-LLLE; ABBB-(D)n-BBBA; AKKK-(D)n-KKKA; ALLL-(D)n-LLLA; EBBB-(D)n-BBBE; EKKK-(D)n-KKKE; ELLL-(D)n-LLLE; ABBB-(D)n-BBBAA; AKKK-(D)n-KKKAA; ALLL-(D)n-LLLAA; EBBB-(D)n-BBBEE; EKKK-(D)n-KKKEE; ELLL-(D)n-LLLEE; ABBB-(D)n-BBBAA; AKKK-(D)n-KKKAA; ALLL-(D)n-LLLAA; EBBB-(D)n-BBBEE; EKKK-(D)n-KKKEE; ELLL-(D)n-LLLEE; AABBB-(D)n-BBB; AAKKK-(D)n-KKK; AALLL-(D)n-LLL; EEBBB-(D)n-BBB; EEKKK-(D)n-KKK; EELLL-(D)n-LLL; AABBB-(D)n-BBB; AAKKK-(D)n-KKK; AALLL-(D)n-LLL; EEBBB-(D)n-BBB; EEKKK-(D)n-KKK; EELLL-(D)n-LLL; AABBB-(D)n-BBBA; AAKKK-(D)n-KKKA; AALLL-(D)n-LLLA; EEBBB-(D)n-BBBE; EEKKK-(D)n-KKKE; EELLL-(D)n-LLLE; AABBB-(D)n-BBBA; AAKKK-(D)n-KKKA; AALLL-(D)n-LLLA; EEBBB-(D)n-BBBE; EEKKK-(D)n-KKKE; EELLL-(D)n-LLLE; ABBAABB-(D)n-BB; AKKAAKK-(D)n-KK; ALLAALLL-(D)n-LL; EBBEEBB-(D)n-BB; EKKEEKK-(D)n-KK; ELLEELL-(D)n-LL; ABBAABB-(D)n-BB; AKKAAKK-(D)n-KK; ALLAALL-(D)n-LL; EBBEEBB-(D)n-BB; EKKEEKK-(D)n-KK; ELLEELL-(D)n-LL; ABBABB-(D)n-BBB; AKKAKK-(D)n-KKK; ALLALLL-(D)n-LLL; EBBEBB-(D)n-BBB; EKKEKK-(D)n-KKK; ELLELL-(D)n-LLL; ABBABB-(D)n-BBB; AKKAKK-(D)n-KKK; ALLALL-(D)n-LLL; EBBEBB-(D)n-BBB; EKKEKK-(D)n-KKK; ELLELL-(D)n-LLL; EEEK-(D)n-EEEEEEEE; EEK-(D)n-EEEEEEEEE; EK-(D)n-EEEEEEEEEE; EK-(D)n-EEEKK; K-(D)n-EEEKEKE; K-(D)n-EEEKEKEE; K-(D)n-EEKEK; EK-(D)n-EEEEKEKE; EK-(D)n-EEEKEK; EEK-(D)n-KEEKE; EK-(D)n-EEKEK; EK-(D)n-KEEK; EEK-(D)n-EEEKEK; EK-(D)n-KEEEKEE; EK-(D)n-EEKEKE; EK-(D)n-EEEKEKE; and EK-(D)n-EEEEKEK;. “A” nucleosides comprise a 2′-modified nucleoside; “B” represents a 2′-4′ bicyclic nucleoside; “K” represents a constrained ethyl nucleoside (cEt); “L” represents an LNA nucleoside; and “E” represents a 2′-MOE modified ribonucleoside; “D” represents a 2′-deoxyribonucleoside; “n” represents the length of the gap segment (Y in the 5′-X-Y-Z-3′ configuration) and is an integer between 1-20. 
     In some embodiments, any one of the gapmers described herein comprises one or more modified nucleoside linkages (e.g., a phosphorothioate linkage) in each of the X, Y, and Z regions. In some embodiments, each internucleoside linkage in the any one of the gapmers described herein is a phosphorothioate linkage. In some embodiments, each of the X, Y, and Z regions independently comprises a mix of phosphorothioate linkages and phosphodiester linkages. In some embodiments, each internucleoside linkage in the gap region Y is a phosphorothioate linkage, the 5′wing region X comprises a mix of phosphorothioate linkages and phosphodiester linkages, and the 3′wing region Z comprises a mix of phosphorothioate linkages and phosphodiester linkages. 
     i. Mixmers 
     In some embodiments, an oligonucleotide described herein may be a mixmer or comprise a mixmer sequence pattern. In general, mixmers are oligonucleotides that comprise both naturally and non-naturally occurring nucleosides or comprise two different types of non-naturally occurring nucleosides typically in an alternating pattern. Mixmers generally have higher binding affinity than unmodified oligonucleotides and may be used to specifically bind a target molecule, e.g., to block a binding site on the target molecule. Generally, mixmers do not recruit an RNase to the target molecule and thus do not promote cleavage of the target molecule. Such oligonucleotides that are incapable of recruiting RNase H have been described, for example, see WO2007/112754 or WO2007/112753. 
     In some embodiments, the mixmer comprises or consists of a repeating pattern of nucleoside analogues and naturally occurring nucleosides, or one type of nucleoside analogue and a second type of nucleoside analogue. However, a mixmer need not comprise a repeating pattern and may instead comprise any arrangement of modified nucleoside s and naturally occurring nucleoside s or any arrangement of one type of modified nucleoside and a second type of modified nucleoside. The repeating pattern, may, for instance be every second or every third nucleoside is a modified nucleoside, such as LNA, and the remaining nucleoside s are naturally occurring nucleosides, such as DNA, or are a 2′ substituted nucleoside analogue such as 2′-MOE or 2′ fluoro analogues, or any other modified nucleoside described herein. It is recognized that the repeating pattern of modified nucleoside, such as LNA units, may be combined with modified nucleoside at fixed positions—e.g. at the 5′ or 3′ termini. 
     In some embodiments, a mixmer does not comprise a region of more than 5, more than 4, more than 3, or more than 2 consecutive naturally occurring nucleosides, such as DNA nucleosides. In some embodiments, the mixmer comprises at least a region consisting of at least two consecutive modified nucleoside, such as at least two consecutive LNAs. In some embodiments, the mixmer comprises at least a region consisting of at least three consecutive modified nucleoside units, such as at least three consecutive LNAs. 
     In some embodiments, the mixmer does not comprise a region of more than 7, more than 6, more than 5, more than 4, more than 3, or more than 2 consecutive nucleoside analogues, such as LNAs. In some embodiments, LNA units may be replaced with other nucleoside analogues, such as those referred to herein. 
     Mixmers may be designed to comprise a mixture of affinity enhancing modified nucleosides, such as in non-limiting example LNA nucleosides and 2′-O-Me nucleosides. In some embodiments, a mixmer comprises modified internucleoside linkages (e.g., phosphorothioate internucleoside linkages or other linkages) between at least two, at least three, at least four, at least five or more nucleosides. 
     A mixmer may be produced using any suitable method. Representative U.S. patents, U.S. patent publications, and PCT publications that teach the preparation of mixmers include U.S. patent publication Nos. US20060128646, US20090209748, US20090298916, US20110077288, and US20120322851, and U.S. Pat. No. 7,687,617. 
     In some embodiments, a mixmer comprises one or more morpholino nucleosides. For example, in some embodiments, a mixmer may comprise morpholino nucleosides mixed (e.g., in an alternating manner) with one or more other nucleosides (e.g., DNA, RNA nucleosides) or modified nucleosides (e.g., LNA, 2′-O-Me nucleosides). 
     In some embodiments, mixmers are useful for splice correcting or exon skipping, for example, as reported in Touznik A., et al.,  LNA/DNA mixmer - based antisense oligonucleotides correct alternative splicing of the SMN 2  gene and restore SMN protein expression in type  1  SMA fibroblasts  Scientific Reports, volume 7, Article number: 3672 (2017), Chen S. et al.,  Synthesis of a Morpholino Nucleic Acid  ( MNA )- Uridine Phosphoramidite, and Exon Skipping Using MNA/ 2′- O - Methyl Mixmer Antisense Oligonucleotide , Molecules 2016, 21, 1582, the contents of each which are incorporated herein by reference. 
     j. RNA Interference (RNAi) 
     In some embodiments, oligonucleotides provided herein may be in the form of small interfering RNAs (siRNA), also known as short interfering RNA or silencing RNA. SiRNA, is a class of double-stranded RNA molecules, typically about 20-25 base pairs in length that target nucleic acids (e.g., mRNAs) for degradation via the RNA interference (RNAi) pathway in cells. Specificity of siRNA molecules may be determined by the binding of the antisense strand of the molecule to its target RNA. Effective siRNA molecules are generally less than 30 to 35 base pairs in length to prevent the triggering of non-specific RNA interference pathways in the cell via the interferon response, although longer siRNA can also be effective. In some embodiments, the siRNA molecules are 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more base pairs in length. In some embodiments, the siRNA molecules are 8 to 30 base pairs in length, 10 to 15 base pairs in length, 10 to 20 base pairs in length, 15 to 25 base pairs in length, 19 to 21 base pairs in length, 21 to 23 base pairs in length. 
     Following selection of an appropriate target RNA sequence, siRNA molecules that comprise a nucleotide sequence complementary to all or a portion of the target sequence, i.e. an antisense sequence, can be designed and prepared using appropriate methods (see, e.g., PCT Publication Number WO 2004/016735; and U.S. Patent Publication Nos. 2004/0077574 and 2008/0081791). The siRNA molecule can be double stranded (i.e. a dsRNA molecule comprising an antisense strand and a complementary sense strand) or single-stranded (i.e. a ssRNA molecule comprising just an antisense strand). The siRNA molecules can comprise a duplex, asymmetric duplex, hairpin or asymmetric hairpin secondary structure, having self-complementary sense and antisense strands. 
     In some embodiments, the antisense strand of the siRNA molecule is 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more nucleotides in length. In some embodiments, the antisense strand is 8 to 50 nucleotides in length, 8 to 40 nucleotides in length, 8 to 30 nucleotides in length, 10 to 15 nucleotides in length, 10 to 20 nucleotides in length, 15 to 25 nucleotides in length, 19 to 21 nucleotides in length, 21 to 23 nucleotides in lengths. 
     In some embodiments, the sense strand of the siRNA molecule is 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more nucleotides in length. In some embodiments, the sense strand is 8 to 50 nucleotides in length, 8 to 40 nucleotides in length, 8 to 30 nucleotides in length, 10 to 15 nucleotides in length, 10 to 20 nucleotides in length, 15 to 25 nucleotides in length, 19 to 21 nucleotides in length, 21 to 23 nucleotides in lengths. 
     In some embodiments, siRNA molecules comprise an antisense strand comprising a region of complementarity to a target region in a target mRNA. In some embodiments, the region of complementarity is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or 100% complementary to a target region in a target mRNA. In some embodiments, the target region is a region of consecutive nucleotides in the target mRNA. In some embodiments, a complementary nucleotide sequence need not be 100% complementary to that of its target to be specifically hybridizable or specific for a target RNA sequence. 
     In some embodiments, siRNA molecules comprise an antisense strand that comprises a region of complementarity to a target RNA sequence and the region of complementarity is in the range of 8 to 15, 8 to 30, 8 to 40, or 10 to 50, or 5 to 50, or 5 to 40 nucleotides in length. In some embodiments, a region of complementarity is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nucleotides in length. In some embodiments, the region of complementarity is complementary with at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 21, at least 22, at least 23, at least 24, at least 25 or more consecutive nucleotides of a target RNA sequence. In some embodiments, siRNA molecules comprise a nucleotide sequence that contains no more than 1, 2, 3, 4, or 5 base mismatches compared to the portion of the consecutive nucleotides of target RNA sequence. In some embodiments, siRNA molecules comprise a nucleotide sequence that has up to 3 mismatches over 15 bases, or up to 2 mismatches over 10 bases. 
     In some embodiments, siRNA molecules comprise an antisense strand comprising a nucleotide sequence that is complementary (e.g., at least 85%, at least 90%, at least 95%, or 100%) to the target RNA sequence of the oligonucleotides provided herein (e.g., in Table 10 and Table 16). In some embodiments, siRNA molecules comprise an antisense strand comprising a nucleotide sequence that is at least 85%, at least 90%, at least 95%, or 100% identical to the oligonucleotides provided herein (e.g., in Table 10 and Table 16). In some embodiments, siRNA molecules comprise an antisense strand comprising at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 21, at least 22, at least 23, at least 24, at least 25 or more consecutive nucleotides of the oligonucleotides provided herein (e.g., in Table 10 and Table 16). 
     Double-stranded siRNA may comprise sense and anti-sense RNA strands that are the same length or different lengths. Double-stranded siRNA molecules can also be assembled from a single oligonucleotide in a stem-loop structure, wherein self-complementary sense and antisense regions of the siRNA molecule are linked by means of a nucleic acid based or non-nucleic acid-based linker(s), as well as circular single-stranded RNA having two or more loop structures and a stem comprising self-complementary sense and antisense strands, wherein the circular RNA can be processed either in vivo or in vitro to generate an active siRNA molecule capable of mediating RNAi. Small hairpin RNA (shRNA) molecules thus are also contemplated herein. These molecules comprise a specific antisense sequence in addition to the reverse complement (sense) sequence, typically separated by a spacer or loop sequence. Cleavage of the spacer or loop provides a single-stranded RNA molecule and its reverse complement, such that they may anneal to form a dsRNA molecule (optionally with additional processing steps that may result in addition or removal of one, two, three or more nucleotides from the 3′ end and/or (e.g., and) the 5′ end of either or both strands). A spacer can be of a sufficient length to permit the antisense and sense sequences to anneal and form a double-stranded structure (or stem) prior to cleavage of the spacer (and, optionally, subsequent processing steps that may result in addition or removal of one, two, three, four, or more nucleotides from the 3′ end and/or (e.g., and) the 5′ end of either or both strands). A spacer sequence is may be an unrelated nucleotide sequence that is situated between two complementary nucleotide sequence regions which, when annealed into a double-stranded nucleic acid, comprise a shRNA. 
     The overall length of the siRNA molecules can vary from about 14 to about 100 nucleotides depending on the type of siRNA molecule being designed. Generally between about 14 and about 50 of these nucleotides are complementary to the RNA target sequence, i.e. constitute the specific antisense sequence of the siRNA molecule. For example, when the siRNA is a double- or single-stranded siRNA, the length can vary from about 14 to about 50 nucleotides, whereas when the siRNA is a shRNA or circular molecule, the length can vary from about 40 nucleotides to about 100 nucleotides. 
     An siRNA molecule may comprise a 3′ overhang at one end of the molecule, The other end may be blunt-ended or have also an overhang (5′ or 3′). When the siRNA molecule comprises an overhang at both ends of the molecule, the length of the overhangs may be the same or different. In one embodiment, the siRNA molecule of the present disclosure comprises 3′ overhangs of about 1 to about 3 nucleotides on both ends of the molecule. In some embodiments, the siRNA molecule comprises 3′ overhangs of about 1 to about 3 nucleotides on the sense strand. In some embodiments, the siRNA molecule comprises 3′ overhangs of about 1 to about 3 nucleotides on the antisense strand. In some embodiments, the siRNA molecule comprises 3′ overhangs of about 1 to about 3 nucleotides on both the sense strand and the antisense strand. 
     In some embodiments, the siRNA molecule comprises one or more modified nucleotides (e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). In some embodiments, the siRNA molecule comprises one or more modified nucleotides and/or (e.g., and) one or more modified internucleotide linkages. In some embodiments, the modified nucleotide is a modified sugar moiety (e.g. a 2′ modified nucleotide). In some embodiments, the siRNA molecule comprises one or more 2′ modified nucleotides, e.g., a 2′-deoxy, 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA). In some embodiments, each nucleotide of the siRNA molecule is a modified nucleotide (e.g., a 2′-modified nucleotide). In some embodiments, the siRNA molecule comprises one or more phosphorodiamidate morpholinos. In some embodiments, each nucleotide of the siRNA molecule is a phosphorodiamidate morpholino. 
     In some embodiments, the siRNA molecule contains a phosphorothioate or other modified internucleotide linkage. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages between at least two nucleotides. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages between all nucleotides. For example, in some embodiments, the siRNA molecule comprises modified internucleotide linkages at the first, second, and/or (e.g., and) third internucleoside linkage at the 5′ or 3′ end of the siRNA molecule. 
     In some embodiments, the modified internucleotide linkages are phosphorus-containing linkages. In some embodiments, phosphorus-containing linkages that may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates comprising 3′alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates comprising 3′-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs of these, and those having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′; see U.S. Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,196; 5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131; 5,399,676; 5,405,939; 5,453,496; 5,455, 233; 5,466,677; 5,476,925; 5,519,126; 5,536,821; 5,541,306; 5,550,111; 5,563, 253; 5,571,799; 5,587,361; and 5,625,050. 
     Any of the modified chemistries or formats of siRNA molecules described herein can be combined with each other. For example, one, two, three, four, five, or more different types of modifications can be included within the same siRNA molecule. 
     In some embodiments, the antisense strand comprises one or more modified nucleotides (e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). In some embodiments, the antisense strand comprises one or more modified nucleotides and/or (e.g., and) one or more modified internucleotide linkages. In some embodiments, the modified nucleotide comprises a modified sugar moiety (e.g. a 2′ modified nucleotide). In some embodiments, the antisense strand comprises one or more 2′ modified nucleotides, e.g., a 2′-deoxy, 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA). In some embodiments, each nucleotide of the antisense strand is a modified nucleotide (e.g., a 2′-modified nucleotide). In some embodiments, the antisense strand comprises one or more phosphorodiamidate morpholinos. In some embodiments, the antisense strand is a phosphorodiamidate morpholino oligomer (PMO). 
     In some embodiments, antisense strand contains a phosphorothioate or other modified internucleotide linkage. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages between at least two nucleotides. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages between all nucleotides. For example, in some embodiments, the antisense strand comprises modified internucleotide linkages at the first, second, and/or (e.g., and) third internucleoside linkage at the 5′ or 3′ end of the siRNA molecule. In some embodiments, the modified internucleotide linkages are phosphorus-containing linkages. In some embodiments, phosphorus-containing linkages that may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates comprising 3′alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates comprising 3′-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs of these, and those having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′; see U.S. Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,196; 5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131; 5,399,676; 5,405,939; 5,453,496; 5,455, 233; 5,466,677; 5,476,925; 5,519,126; 5,536,821; 5,541,306; 5,550,111; 5,563, 253; 5,571,799; 5,587,361; and 5,625,050. 
     Any of the modified chemistries or formats of the antisense strand described herein can be combined with each other. For example, one, two, three, four, five, or more different types of modifications can be included within the same antisense strand. 
     In some embodiments, the sense strand comprises one or more modified nucleotides (e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). In some embodiments, the sense strand comprises one or more modified nucleotides and/or (e.g., and) one or more modified internucleotide linkages. In some embodiments, the modified nucleotide is a modified sugar moiety (e.g. a 2′ modified nucleotide). In some embodiments, the sense strand comprises one or more 2′ modified nucleotides, e.g., a 2′-deoxy, 2′-fluoro (2′-F), 2′-O-methyl (2′-O-Me), 2′-O-methoxyethyl (2′-MOE), 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA). In some embodiments, each nucleotide of the sense strand is a modified nucleotide (e.g., a 2′-modified nucleotide). In some embodiments, the sense strand comprises one or more phosphorodiamidate morpholinos. In some embodiments, the antisense strand is a phosphorodiamidate morpholino oligomer (PMO). In some embodiments, the sense strand contains a phosphorothioate or other modified internucleotide linkage. In some embodiments, the sense strand comprises phosphorothioate internucleoside linkages. In some embodiments, the sense strand comprises phosphorothioate internucleoside linkages between at least two nucleotides. In some embodiments, the sense strand comprises phosphorothioate internucleoside linkages between all nucleotides. For example, in some embodiments, the sense strand comprises modified internucleotide linkages at the first, second, and/or (e.g., and) third internucleoside linkage at the 5′ or 3′ end of the sense strand. 
     In some embodiments, the modified internucleotide linkages are phosphorus-containing linkages. In some embodiments, phosphorus-containing linkages that may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates comprising 3′alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates comprising 3′-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs of these, and those having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′; see U.S. Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,196; 5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131; 5,399,676; 5,405,939; 5,453,496; 5,455, 233; 5,466,677; 5,476,925; 5,519,126; 5,536,821; 5,541,306; 5,550,111; 5,563, 253; 5,571,799; 5,587,361; and 5,625,050. 
     Any of the modified chemistries or formats of the sense strand described herein can be combined with each other. For example, one, two, three, four, five, or more different types of modifications can be included within the same sense strand. 
     In some embodiments, the antisense or sense strand of the siRNA molecule comprises modifications that enhance or reduce RNA-induced silencing complex (RISC) loading. In some embodiments, the antisense strand of the siRNA molecule comprises modifications that enhance RISC loading. In some embodiments, the sense strand of the siRNA molecule comprises modifications that reduce RISC loading and reduce off-target effects. In some embodiments, the antisense strand of the siRNA molecule comprises a 2′-O-methoxyethyl (2′-MOE) modification. The addition of the 2′-O-methoxyethyl (2′-MOE) group at the cleavage site improves both the specificity and silencing activity of siRNAs by facilitating the oriented RNA-induced silencing complex (RISC) loading of the modified strand, as described in Song et al., (2017) Mol Ther Nucleic Acids 9:242-250, incorporated herein by reference in its entirety. In some embodiments, the antisense strand of the siRNA molecule comprises a 2′-OMe-phosphorodithioate modification, which increases RISC loading as described in Wu et al., (2014) Nat Commun 5:3459, incorporated herein by reference in its entirety. 
     In some embodiments, the sense strand of the siRNA molecule comprises a 5′-morpholino, which reduces RISC loading of the sense strand and improves antisense strand selection and RNAi activity, as described in Kumar et al., (2019) Chem Commun (Camb) 55(35):5139-5142, incorporated herein by reference in its entirety. In some embodiments, the sense strand of the siRNA molecule is modified with a synthetic RNA-like high affinity nucleotide analogue, Locked Nucleic Acid (LNA), which reduces RISC loading of the sense strand and further enhances antisense strand incorporation into RISC, as described in Elman et al., (2005) Nucleic Acids Res. 33(1): 439-447, incorporated herein by reference in its entirety. In some embodiments, the sense strand of the siRNA molecule comprises a 5′ unlocked nucleic acid (UNA) modification, which reduce RISC loading of the sense strand and improve silencing potency of the antisense strand, as described in Snead et al., (2013) Mol Ther Nucleic Acids 2(7):e103, incorporated herein by reference in its entirety. In some embodiments, the sense strand of the siRNA molecule comprises a 5-nitroindole modification, which decreased the RNAi potency of the sense strand and reduces off-target effects as described in Zhang et al., (2012) Chembiochem 13(13):1940-1945, incorporated herein by reference in its entirety. In some embodiments, the sense strand comprises a 2′-O′methyl (2′-0-Me) modification, which reduces RISC loading and the off-target effects of the sense strand, as described in Zheng et al., FASEB (2013) 27(10): 4017-4026, incorporated herein by reference in its entirety. In some embodiments, the sense strand of the siRNA molecule is fully substituted with morpholino, 2′-MOE or 2′-O-Me residues, and are not recognized by RISC as described in Kole et al., (2012) Nature reviews. Drug Discovery 11(2):125-140, incorporated herein by reference in its entirety. In some embodiments the antisense strand of the siRNA molecule comprises a 2′-MOE modification and the sense strand comprises an 2′-O-Me modification (see e.g., Song et al., (2017) Mol Ther Nucleic Acids 9:242-250). In some embodiments at least one (e.g., at least 2, at least 3, at least 4, at least 5, at least 10) siRNA molecule is linked (e.g., covalently) to a muscle-targeting agent. In some embodiments, the muscle-targeting agent may comprise, or consist of, a nucleic acid (e.g., DNA or RNA), a peptide (e.g., an antibody), a lipid (e.g., a microvesicle), or a sugar moiety (e.g., a polysaccharide). In some embodiments, the muscle-targeting agent is an antibody. In some embodiments, the muscle-targeting agent is an anti-transferrin receptor antibody (e.g., any one of the anti-TfR antibodies provided herein). In some embodiments, the muscle-targeting agent may be linked to the 5′ end of the sense strand of the siRNA molecule. In some embodiments, the muscle-targeting agent may be linked to the 3′ end of the sense strand of the siRNA molecule. In some embodiments, the muscle-targeting agent may be linked internally to the sense strand of the siRNA molecule. In some embodiments, the muscle-targeting agent may be linked to the 5′ end of the antisense strand of the siRNA molecule. In some embodiments, the muscle-targeting agent may be linked to the 3′ end of the antisense strand of the siRNA molecule. In some embodiments, the muscle-targeting agent may be linked internally to the antisense strand of the siRNA molecule. 
     k. microRNA (miRNAs) 
     In some embodiments, an oligonucleotide may be a microRNA (miRNA). MicroRNAs (referred to as “miRNAs”) are small non-coding RNAs, belonging to a class of regulatory molecules that control gene expression by binding to complementary sites on a target RNA transcript. Typically, miRNAs are generated from large RNA precursors (termed pri-miRNAs) that are processed in the nucleus into approximately 70 nucleotide pre-miRNAs, which fold into imperfect stem-loop structures. These pre-miRNAs typically undergo an additional processing step within the cytoplasm where mature miRNAs of 18-25 nucleotides in length are excised from one side of the pre-miRNA hairpin by an RNase III enzyme, Dicer. 
     As used herein, miRNAs including pri-miRNA, pre-miRNA, mature miRNA or fragments of variants thereof that retain the biological activity of mature miRNA. In one embodiment, the size range of the miRNA can be from 21 nucleotides to 170 nucleotides. In one embodiment the size range of the miRNA is from 70 to 170 nucleotides in length. In another embodiment, mature miRNAs of from 21 to 25 nucleotides in length can be used. 
     l. Aptamers 
     In some embodiments, oligonucleotides provided herein may be in the form of aptamers. Generally, in the context of molecular payloads, aptamer is any nucleic acid that binds specifically to a target, such as a small molecule, protein, nucleic acid in a cell. In some embodiments, the aptamer is a DNA aptamer or an RNA aptamer. In some embodiments, a nucleic acid aptamer is a single-stranded DNA or RNA (ssDNA or ssRNA). It is to be understood that a single-stranded nucleic acid aptamer may form helices and/or (e.g., and) loop structures. The nucleic acid that forms the nucleic acid aptamer may comprise naturally occurring nucleotides, modified nucleotides, naturally occurring nucleotides with hydrocarbon linkers (e.g., an alkylene) or a polyether linker (e.g., a PEG linker) inserted between one or more nucleotides, modified nucleotides with hydrocarbon or PEG linkers inserted between one or more nucleotides, or a combination of thereof. Exemplary publications and patents describing aptamers and method of producing aptamers include, e.g., Lorsch and Szostak, 1996; Jayasena, 1999; U.S. Pat. Nos. 5,270,163; 5,567,588; 5,650,275; 5,670,637; 5,683,867; 5,696,249; 5,789,157; 5,843,653; 5,864,026; 5,989,823; 6,569,630; 8,318,438 and PCT application WO 99/31275, each incorporated herein by reference. 
     m. Ribozymes 
     In some embodiments, oligonucleotides provided herein may be in the form of a ribozyme. A ribozyme (ribonucleic acid enzyme) is a molecule, typically an RNA molecule, that is capable of performing specific biochemical reactions, similar to the action of protein enzymes. Ribozymes are molecules with catalytic activities including the ability to cleave at specific phosphodiester linkages in RNA molecules to which they have hybridized, such as mRNAs, RNA-containing substrates, lncRNAs, and ribozymes, themselves. 
     Ribozymes may assume one of several physical structures, one of which is called a “hammerhead.” A hammerhead ribozyme is composed of a catalytic core containing nine conserved bases, a double-stranded stem and loop structure (stem-loop II), and two regions complementary to the target RNA flanking regions the catalytic core. The flanking regions enable the ribozyme to bind to the target RNA specifically by forming double-stranded stems I and III. Cleavage occurs in cis (i.e., cleavage of the same RNA molecule that contains the hammerhead motif) or in trans (cleavage of an RNA substrate other than that containing the ribozyme) next to a specific ribonucleotide triplet by a transesterification reaction from a 3′, 5′-phosphate diester to a 2′, 3′-cyclic phosphate diester. Without wishing to be bound by theory, it is believed that this catalytic activity requires the presence of specific, highly conserved sequences in the catalytic region of the ribozyme. 
     Modifications in ribozyme structure have also included the substitution or replacement of various non-core portions of the molecule with non-nucleotidic molecules. For example, Benseler et al. (J. Am. Chem. Soc. (1993) 115:8483-8484) disclosed hammerhead-like molecules in which two of the base pairs of stem II, and all four of the nucleotides of loop II were replaced with non-nucleoside linkers based on hexaethylene glycol, propanediol, bis(triethylene glycol) phosphate, tris(propanediol)bisphosphate, or bis(propanediol) phosphate. Ma et al. (Biochem. (1993) 32:1751-1758; Nucleic Acids Res. (1993) 21:2585-2589) replaced the six nucleotide loop of the TAR ribozyme hairpin with non-nucleotidic, ethylene glycol-related linkers. Thomson et al. (Nucleic Acids Res. (1993) 21:5600-5603) replaced loop II with linear, non-nucleotidic linkers of 13, 17, and 19 atoms in length. 
     Ribozyme oligonucleotides can be prepared using well known methods (see, e.g., PCT Publications WO9118624; WO9413688; WO9201806; and WO 92/07065; and U.S. Pat. No. 5,436,143 and 5,650,502) or can be purchased from commercial sources (e.g., US Biochemicals) and, if desired, can incorporate nucleotide analogs to increase the resistance of the oligonucleotide to degradation by nucleases in a cell. The ribozyme may be synthesized in any known manner, e.g., by use of a commercially available synthesizer produced, e.g., by Applied Biosystems, Inc. or Milligen. The ribozyme may also be produced in recombinant vectors by conventional means. See, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory (Current edition). The ribozyme RNA sequences maybe synthesized conventionally, for example, by using RNA polymerases such as T7 or SP6. 
     n. Guide Nucleic Acids 
     In some embodiments, oligonucleotides are guide nucleic acid, e.g., guide RNA (gRNA) molecules. Generally, a guide RNA is a short synthetic RNA composed of (1) a scaffold sequence that binds to a nucleic acid programmable DNA binding protein (napDNAbp), such as Cas9, and (2) a nucleotide spacer portion that defines the DNA target sequence (e.g., genomic DNA target) to which the gRNA binds in order to bring the nucleic acid programmable DNA binding protein in proximity to the DNA target sequence. In some embodiments, the napDNAbp is a nucleic acid-programmable protein that forms a complex with (e.g., binds or associates with) one or more RNA(s) that targets the nucleic acid-programmable protein to a target DNA sequence (e.g., a target genomic DNA sequence). In some embodiments, a nucleic acid-programmable nuclease, when in a complex with an RNA, may be referred to as a nuclease:RNA complex. Guide RNAs can exist as a complex of two or more RNAs, or as a single RNA molecule. 
     Guide RNAs (gRNAs) that exist as a single RNA molecule may be referred to as single-guide RNAs (sgRNAs), though gRNA is also used to refer to guide RNAs that exist as either single molecules or as a complex of two or more molecules. Typically, gRNAs that exist as a single RNA species comprise two domains: (1) a domain that shares homology to a target nucleic acid (i.e., directs binding of a Cas9 complex to the target); and (2) a domain that binds a Cas9 protein. In some embodiments, domain (2) corresponds to a sequence known as a tracrRNA and comprises a stem-loop structure. In some embodiments, domain (2) is identical or homologous to a tracrRNA as provided in Jinek et al., Science 337:816-821 (2012), the entire contents of which is incorporated herein by reference. 
     In some embodiments, a gRNA comprises two or more of domains (1) and (2), and may be referred to as an extended gRNA. For example, an extended gRNA will bind two or more Cas9 proteins and bind a target nucleic acid at two or more distinct regions, as described herein. The gRNA comprises a nucleotide sequence that complements a target site, which mediates binding of the nuclease/RNA complex to said target site, providing the sequence specificity of the nuclease:RNA complex. In some embodiments, the RNA-programmable nuclease is the (CRISPR-associated system) Cas9 endonuclease, for example, Cas9 (Csn1) from  Streptococcus pyogenes  (see, e.g., “Complete genome sequence of an M1 strain of  Streptococcus pyogenes .” Ferretti J. J., McShan W. M., Ajdic D. J., Savic D. J., Savic G., Lyon K., Primeaux C., Sezate S., Suvorov A. N., Kenton S., Lai H. S., Lin S. P., Qian Y., Jia H. G., Najar F. Z., Ren Q., Zhu H., Song L., White J., Yuan X., Clifton S. W., Roe B. A., McLaughlin R. E., Proc. Natl. Acad. Sci. U.S.A. 98:4658-4663 (2001); “CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III.” Deltcheva E., Chylinski K., Sharma C. M., Gonzales K., Chao Y., Pirzada Z. A., Eckert M. R., Vogel J., Charpentier E., Nature 471:602-607 (2011); and “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity.” Jinek M., Chylinski K., Fonfara I., Hauer M., Doudna J. A., Charpentier E. Science 337:816-821 (2012), the entire contents of each of which are incorporated herein by reference. 
     o. Multimers 
     In some embodiments, molecular payloads may comprise multimers (e.g., concatemers) of 2 or more oligonucleotides connected by a linker. In this way, in some embodiments, the oligonucleotide loading of a complex/conjugate can be increased beyond the available linking sites on a targeting agent (e.g., available thiol sites on an antibody) or otherwise tuned to achieve a particular payload loading content. Oligonucleotides in a multimer can be the same or different (e.g., targeting different genes or different sites on the same gene or products thereof). 
     In some embodiments, multimers comprise 2 or more oligonucleotides linked together by a cleavable linker. However, in some embodiments, multimers comprise 2 or more oligonucleotides linked together by a non-cleavable linker. In some embodiments, a multimer comprises 2, 3, 4, 5, 6, 7, 8, 9, 10 or more oligonucleotides linked together. In some embodiments, a multimer comprises 2 to 5, 2 to 10 or 4 to 20 oligonucleotides linked together. 
     In some embodiments, a multimer comprises 2 or more oligonucleotides linked end-to-end (in a linear arrangement). In some embodiments, a multimer comprises 2 or more oligonucleotides linked end-to-end via a oligonucleotide based linker (e.g., poly-dT linker, an abasic linker). In some embodiments, a multimer comprises a 5′ end of one oligonucleotide linked to a 3′ end of another oligonucleotide. In some embodiments, a multimer comprises a 3′ end of one oligonucleotide linked to a 3′ end of another oligonucleotide. In some embodiments, a multimer comprises a 5′ end of one oligonucleotide linked to a 5′ end of another oligonucleotide. Still, in some embodiments, multimers can comprise a branched structure comprising multiple oligonucleotides linked together by a branching linker. 
     Further examples of multimers that may be used in the complexes provided herein are disclosed, for example, in US Patent Application Number 2015/0315588 A1, entitled Methods of delivering multiple targeting oligonucleotides to a cell using cleavable linkers, which was published on Nov. 5, 2015; US Patent Application Number 2015/0247141 A1, entitled Multimeric Oligonucleotide Compounds, which was published on Sep. 3, 2015, US Patent Application Number US 2011/0158937 A1, entitled Immunostimulatory Oligonucleotide Multimers, which was published on Jun. 30, 2011; and U.S. Pat. No. 5,693,773, entitled Triplex-Forming Antisense Oligonucleotides Having Abasic Linkers Targeting Nucleic Acids Comprising Mixed Sequences Of Purines And Pyrimidines, which issued on Dec. 2, 1997, the contents of each of which are incorporated herein by reference in their entireties. 
     ii. Small Molecules: 
     Any suitable small molecule may be used as a molecular payload, as described herein. In some embodiments, the small molecule is as described in US Patent Application Publication 2016052914A1, published on Feb. 25, 2016, entitled “Compounds And Methods For Myotonic Dystrophy Therapy”. Further examples of small molecule payloads are provided in Lopez-Morato M, et al., Small Molecules Which Improve Pathogenesis of Myotonic Dystrophy Type 1, (Review) Front. Neurol., 18 May 2018. For example, in some embodiments, the small molecule is an MBNL1 upregulator such as phenylbuthazone, ketoprofen, ISOX, or vorinostat. In some embodiments, the small molecule is an H-Ras pathway inhibitor such as manumycin A. In some embodiments, the small molecule is a protein kinase modulator such as Ro-318220, C16, C51, Metformin, AICAR, lithium chloride, TDZD-8 or Bio. In some embodiments, the small molecule is a plant alkaloid such as harmine. In some embodiments, the small molecule is a transcription inhibitor such as pentamidine, propamidine, heptamidiine or actinomycin D. In some embodiments, the small molecule is an inhibitor of Glycogen synthase kinase 3 beta (GSK3B), for example, as disclosed in Jones K, et al., GSK3β mediates muscle pathology in myotonic dystrophy. J Clin Invest. 2012 December; 122(12):4461-72; and Wei C, et al., GSK3β is a new therapeutic target for myotonic dystrophy type 1. Rare Dis. 2013; 1: e26555; and Palomo V, et al., Subtly Modulating Glycogen Synthase Kinase 3 (3: Allosteric Inhibitor Development and Their Potential for the Treatment of Chronic Diseases. J Med Chem. 2017 Jun. 22; 60(12):4983-5001, the contents of each of which are incorporated herein by reference in their entireties. In some embodiments, the small molecule is a substituted pyrido[2,3-d]pyrimidines and pentamidine-like compound, as disclosed in Gonzalez A L, et al., In silico discovery of substituted pyrido[2,3-d]pyrimidines and pentamidine-like compounds with biological activity in myotonic dystrophy models. PLoS One. 2017 Jun. 5; 12(6):e0178931, the contents of which are incorporated herein by reference in its entirety. In some embodiments, the small molecule is an MBNL1 modulator, for example, as disclosed in: Zhange F, et al., A flow cytometry-based screen identifies MBNL1 modulators that rescue splicing defects in myotonic dystrophy type I. Hum Mol Genet. 2017 Aug. 15; 26(16):3056-3068, the contents of which are incorporated herein by reference in its entirety. 
     iii. Peptides 
     Any suitable peptide or protein may be used as a molecular payload, as described herein. A peptide or protein payload may correspond to a sequence of a protein that preferentially binds to a nucleic acid, e.g. a disease-associated repeat, or a protein, e.g. MBNL1, found in muscle cells. In some embodiments, peptides or proteins may be produced, synthesized, and/or (e.g., and) derivatized using several methodologies, e.g. phage displayed peptide libraries, one-bead one-compound peptide libraries, or positional scanning synthetic peptide combinatorial libraries. Exemplary methodologies have been characterized in the art and are incorporated by reference (Gray, B. P. and Brown, K. C. “Combinatorial Peptide Libraries: Mining for Cell-Binding Peptides” Chem Rev. 2014, 114:2, 1020-1081.; Samoylova, T. I. and Smith, B. F. “Elucidation of muscle-binding peptides by phage display screening.” Muscle Nerve, 1999, 22:4. 460-6.). 
     In some embodiments, the peptide is as described in US Patent Application 2018/0021449, published on Jan. 25, 2018, “Antisense conjugates for decreasing expression of DMPK”. In some embodiments, the peptide is as described in Garcia-Lopez et al., “In vivo discovery of a peptide that prevents CUG-RNA hairpin formation and reverses RNA toxicity in myotonic dystrophy models”, PNAS Jul. 19, 2011. 108 (29) 11866-11871. In some embodiments, the peptide or protein may target, e.g., bind to, a disease-associated repeat, e.g. a RNA CUG repeat expansion. 
     In some embodiments, the peptide or protein comprises a fragment of an MBNL protein, e.g., MBNL1. In some embodiments, the peptide or protein comprises at least one zinc finger. In some embodiments, the peptide or protein may comprise about 2-25 amino acids, about 2-20 amino acids, about 2-15 amino acids, about 2-10 amino acids, or about 2-5 amino acids. The peptide or protein may comprise naturally-occurring amino acids, e.g. cysteine, alanine, or non-naturally-occurring or modified amino acids. Non-naturally occurring amino acids include β-amino acids, homo-amino acids, proline derivatives, 3-substituted alanine derivatives, linear core amino acids, N-methyl amino acids, and others known in the art. In some embodiments, the peptide may be linear; in other embodiments, the peptide may be cyclic, e.g. bicyclic. 
     iv. Nucleic Acid Constructs 
     Any suitable gene expression construct may be used as a molecular payload, as described herein. In some embodiments, a gene expression construct may be a vector or a cDNA fragment. In some embodiments, a gene expression construct may be messenger RNA (mRNA). In some embodiments, a mRNA used herein may be a modified mRNA, e.g., as described in U.S. Pat. No. 8,710,200, issued on Apr. 24, 2014, entitled “Engineered nucleic acids encoding a modified erythropoietin and their expression”. In some embodiments, a mRNA may comprise a 5′ methyl cap. In some embodiments, a mRNA may comprise a polyA tail, optionally of up to 160 nucleotides in length. A gene expression construct may encode a sequence of a protein that preferentially binds to a nucleic acid, e.g. a disease-associated repeat, or a protein, e.g. MBNL1, found in muscle cells. In some embodiments, the gene expression construct may be expressed, e.g., overexpressed, within the nucleus of a muscle cell. In some embodiments, the gene expression construct encodes a MBNL protein, e.g., MBNL1. In some embodiments, the gene expression constructs encodes a protein that comprises at least one zinc finger. In some embodiments, the gene expression construct encodes a protein that binds to a disease-associated repeat. In some embodiments, the gene expression construct encodes a protein that leads to a reduction in the expression of a disease-associated repeat. In some embodiments, the gene expression construct encodes a gene editing enzyme. Additional examples of nucleic acid constructs that may be used as molecular payloads are provided in International Patent Application Publication WO2017152149A1, published on Sep. 19, 2017, entitled, “Closed-Ended Linear Duplex Dna For Non-Viral Gene Transfer”; U.S. Pat. No. 8,853,377B2, issued on Oct. 7, 2014, entitled, “mRNA For Use In Treatment Of Human Genetic Diseases”; and U.S. Pat. No. 8,822,663B2, issued on Sep. 2, 2014, Engineered Nucleic Acids And Methods Of Use Thereof,” the contents of each of which are incorporated herein by reference in their entireties. 
     Further examples of complexes and molecular payloads (e.g., oligonucleotides useful for targeting muscle genes) are provided in International Patent Application Publication WO2020/028861, published on Feb. 6, 2020, entitled, “MUSCLE TARGETING COMPLEXES AND USES THEREOF FOR TREATING MYOTONIC DYSTROPHY”; and International Patent Application Publication WO2020/028857, published on Feb. 6, 2020, entitled, “MUSCLE-TARGETING COMPLEXES AND USES THEREOF”, the contents of each of which are incorporated herein by reference. 
     C. Linkers 
     Complexes described herein generally comprise a linker that connects a muscle-targeting agent to a molecular payload. A linker comprises at least one covalent bond. In some embodiments, a linker may be a single bond, e.g., a disulfide bond or disulfide bridge, that connects a muscle-targeting agent to a molecular payload. However, in some embodiments, a linker may connect a muscle-targeting agent to a molecular payload through multiple covalent bonds. In some embodiments, a linker may be a cleavable linker. However, in some embodiments, a linker may be a non-cleavable linker. A linker is generally stable in vitro and in vivo, and may be stable in certain cellular environments. Additionally, generally a linker does not negatively impact the functional properties of either the muscle-targeting agent or the molecular payload. Examples and methods of synthesis of linkers are known in the art (see, e.g. Kline, T. et al. “Methods to Make Homogenous Antibody Drug Conjugates.” Pharmaceutical Research, 2015, 32:11, 3480-3493.; Jain, N. et al. “Current ADC Linker Chemistry” Pharm Res. 2015, 32:11, 3526-3540.; McCombs, J. R. and Owen, S. C. “Antibody Drug Conjugates: Design and Selection of Linker, Payload and Conjugation Chemistry” AAPS J. 2015, 17:2, 339-351.). 
     A precursor to a linker typically will contain two different reactive species that allow for attachment to both the muscle-targeting agent and a molecular payload. In some embodiments, the two different reactive species may be a nucleophile and/or (e.g., and) an electrophile. In some embodiments, a linker is connected to a muscle-targeting agent via conjugation to a lysine residue or a cysteine residue of the muscle-targeting agent. In some embodiments, a linker is connected to a cysteine residue of a muscle-targeting agent via a maleimide-containing linker, wherein optionally the maleimide-containing linker comprises a maleimidocaproyl or maleimidomethyl cyclohexane-1-carboxylate group. In some embodiments, a linker is connected to a cysteine residue of a muscle-targeting agent or thiol functionalized molecular payload via a 3-arylpropionitrile functional group. In some embodiments, a linker is connected to a lysine residue of an anti-TfR antibody. In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) a molecular payload via an amide bond, a carbamate bond, a hydrazide, a triazole, a thioether or a disulfide bond. 
     i. Cleavable Linkers 
     A cleavable linker may be a protease-sensitive linker, a pH-sensitive linker, or a glutathione-sensitive linker. These linkers are generally cleavable only intracellularly and are preferably stable in extracellular environments, e.g. extracellular to a muscle cell. 
     Protease-sensitive linkers are cleavable by protease enzymatic activity. These linkers typically comprise peptide sequences and may be 2-10 amino acids, about 2-5 amino acids, about 5-10 amino acids, about 10 amino acids, about 5 amino acids, about 3 amino acids, or about 2 amino acids in length. In some embodiments, a peptide sequence may comprise naturally-occurring amino acids, e.g. cysteine, alanine, or non-naturally-occurring or modified amino acids. Non-naturally occurring amino acids include β-amino acids, homo-amino acids, proline derivatives, 3-substituted alanine derivatives, linear core amino acids, N-methyl amino acids, and others known in the art. In some embodiments, a protease-sensitive linker comprises a valine-citrulline or alanine-citrulline dipeptide sequence. In some embodiments, a protease-sensitive linker can be cleaved by a lysosomal protease, e.g. cathepsin B, and/or (e.g., and) an endosomal protease. 
     A pH-sensitive linker is a covalent linkage that readily degrades in high or low pH environments. In some embodiments, a pH-sensitive linker may be cleaved at a pH in a range of 4 to 6. In some embodiments, a pH-sensitive linker comprises a hydrazone or cyclic acetal. In some embodiments, a pH-sensitive linker is cleaved within an endosome or a lysosome. 
     In some embodiments, a glutathione-sensitive linker comprises a disulfide moiety. In some embodiments, a glutathione-sensitive linker is cleaved by an disulfide exchange reaction with a glutathione species inside a cell. In some embodiments, the disulfide moiety further comprises at least one amino acid, e.g. a cysteine residue. 
     In some embodiments, the linker is a Val-cit linker (e.g., as described in U.S. Pat. No. 6,214,345, incorporated herein by reference). In some embodiments, before conjugation, the val-cit linker has a structure of: 
     
       
         
         
             
             
         
       
     
     In some embodiments, after conjugation, the val-cit linker has a structure of: 
     
       
         
         
             
             
         
       
     
     In some embodiments, the Val-cit linker is attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation). In some embodiments, before click chemistry conjugation, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10. In some embodiments, n is 3. 
     In some embodiments, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) is conjugated (e.g., via a different chemical moiety) to a molecular payload (e.g., an oligonucleotide). In some embodiments, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) and is conjugated to a molecular payload (e.g., an oligonucleotide) has the structure of (before click chemistry conjugation): 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10. In some embodiments, n is 3. 
     In some embodiments, after conjugation to a molecular payload (e.g., an oligonucleotide) and, the val-cit linker has a structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10, and wherein m is any number from 0-10. In some embodiments, n is 3 and m is 4. 
     ii. Non-Cleavable Linkers 
     In some embodiments, non-cleavable linkers may be used. Generally, a non-cleavable linker cannot be readily degraded in a cellular or physiological environment. In some embodiments, a non-cleavable linker comprises an optionally substituted alkyl group, wherein the substitutions may include halogens, hydroxyl groups, oxygen species, and other common substitutions. In some embodiments, a linker may comprise an optionally substituted alkyl, an optionally substituted alkylene, an optionally substituted arylene, a heteroarylene, a peptide sequence comprising at least one non-natural amino acid, a truncated glycan, a sugar or sugars that cannot be enzymatically degraded, an azide, an alkyne-azide, a peptide sequence comprising a LPXTG sequence (SEQ ID NO: 733), a thioether, a biotin, a biphenyl, repeating units of polyethylene glycol or equivalent compounds, acid esters, acid amides, sulfamides, and/or (e.g., and) an alkoxy-amine linker. In some embodiments, sortase-mediated ligation will be utilized to covalently link a muscle-targeting agent comprising a LPXTG sequence (SEQ ID NO: 733) to a molecular payload comprising a (G) n  sequence (see, e.g. Proft T. Sortase-mediated protein ligation: an emerging biotechnology tool for protein modification and immobilization. Biotechnol Lett. 2010, 32(1):1-10.). In some embodiments, a linker comprises a LPXTG sequence (SEQ ID NO: 733), where X is any amino acid. 
     In some embodiments, a linker may comprise a substituted alkylene, an optionally substituted alkenylene, an optionally substituted alkynylene, an optionally substituted cycloalkylene, an optionally substituted cycloalkenylene, an optionally substituted arylene, an optionally substituted heteroarylene further comprising at least one heteroatom selected from N, O, and S; an optionally substituted heterocyclylene further comprising at least one heteroatom selected from N, O, and S; an imino, an optionally substituted nitrogen species, an optionally substituted oxygen species O, an optionally substituted sulfur species, or a poly(alkylene oxide), e.g. polyethylene oxide or polypropylene oxide. 
     iii. Linker Conjugation 
     In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload via a phosphate, thioether, ether, carbon-carbon, a carbamate, or amide bond. In some embodiments, a linker is connected to an oligonucleotide through a phosphate or phosphorothioate group, e.g. a terminal phosphate of an oligonucleotide backbone. In some embodiments, a linker is connected to an muscle-targeting agent, e.g. an antibody, through a lysine or cysteine residue present on the muscle-targeting agent 
     In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by a cycloaddition reaction between an azide and an alkyne to form a triazole, wherein the azide and the alkyne may be located on the muscle-targeting agent, molecular payload, or the linker. In some embodiments, an alkyne may be a cyclic alkyne, e.g., a cyclooctyne. In some embodiments, an alkyne may be bicyclononyne (also known as bicyclo[6.1.0]nonyne or BCN) or substituted bicyclononyne. In some embodiments, a cyclooctane is as described in International Patent Application Publication WO2011136645, published on Nov. 3, 2011, entitled, “Fused Cyclooctyne Compounds And Their Use In Metal free Click Reactions”. In some embodiments, an azide may be a sugar or carbohydrate molecule that comprises an azide. In some embodiments, an azide may be 6-azido-6-deoxygalactose or 6-azido-N-acetylgalactosamine. In some embodiments, a sugar or carbohydrate molecule that comprises an azide is as described in International Patent Application Publication WO2016170186, published on Oct. 27, 2016, entitled, “Process For The Modification Of A Glycoprotein Using A Glycosyltransferase That Is Or Is Derived From A β(1,4)-N-Acetylgalactosaminyltransferase”. In some embodiments, a cycloaddition reaction between an azide and an alkyne to form a triazole, wherein the azide and the alkyne may be located on the muscle-targeting agent, molecular payload, or the linker is as described in International Patent Application Publication WO2014065661, published on May 1, 2014, entitled, “Modified antibody, antibody-conjugate and process for the preparation thereof”; or International Patent Application Publication WO2016170186, published on Oct. 27, 2016, entitled, “Process For The Modification Of A Glycoprotein Using A Glycosyltransferase That Is Or Is Derived From A β(1,4)-N-Acetylgalactosaminyltransferase”. 
     In some embodiments, a linker further comprises a spacer, e.g., a polyethylene glycol spacer or an acyl/carbomoyl sulfamide spacer, e.g., a HydraSpace™ spacer. In some embodiments, a spacer is as described in Verkade, J. M. M. et al., “ A Polar Sulfamide Spacer Significantly Enhances the Manufacturability, Stability, and Therapeutic Index of Antibody - Drug Conjugates ”, Antibodies, 2018, 7, 12. 
     In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by the Diels-Alder reaction between a dienophile and a diene/hetero-diene, wherein the dienophile and the diene/hetero-diene may be located on the muscle-targeting agent, molecular payload, or the linker. In some embodiments a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by other pericyclic reactions, e.g. ene reaction. In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by an amide, thioamide, or sulfonamide bond reaction. In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by a condensation reaction to form an oxime, hydrazone, or semicarbazide group existing between the linker and the muscle-targeting agent and/or (e.g., and) molecular payload. 
     In some embodiments, a linker is connected to a muscle-targeting agent and/or (e.g., and) molecular payload by a conjugate addition reactions between a nucleophile, e.g. an amine or a hydroxyl group, and an electrophile, e.g. a carboxylic acid, carbonate, or an aldehyde. In some embodiments, a nucleophile may exist on a linker and an electrophile may exist on a muscle-targeting agent or molecular payload prior to a reaction between a linker and a muscle-targeting agent or molecular payload. In some embodiments, an electrophile may exist on a linker and a nucleophile may exist on a muscle-targeting agent or molecular payload prior to a reaction between a linker and a muscle-targeting agent or molecular payload. In some embodiments, an electrophile may be an azide, a pentafluorophenyl, a silicon centers, a carbonyl, a carboxylic acid, an anhydride, an isocyanate, a thioisocyanate, a succinimidyl ester, a sulfosuccinimidyl ester, a maleimide, an alkyl halide, an alkyl pseudohalide, an epoxide, an episulfide, an aziridine, an aryl, an activated phosphorus center, and/or (e.g., and) an activated sulfur center. In some embodiments, a nucleophile may be an optionally substituted alkene, an optionally substituted alkyne, an optionally substituted aryl, an optionally substituted heterocyclyl, a hydroxyl group, an amino group, an alkylamino group, an anilido group, or a thiol group. 
     In some embodiments, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) is conjugated to the anti-TfR antibody by a structure of: 
     
       
         
         
             
             
         
       
     
     wherein m is any number from 0-10. In some embodiments, m is 4. 
     In some embodiments, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) is conjugated to an anti-TfR antibody having a structure of: 
     
       
         
         
             
             
         
       
     
     wherein m is any number from 0-10. In some embodiments, m is 4. 
     In some embodiments, the val-cit linker attached to a reactive chemical moiety (e.g., SPAAC for click chemistry conjugation) and is conjugated to an anti-TfR antibody has a structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10, wherein m is any number from 0-10. In some embodiments, n is 3 and/or (e.g., and) m is 4. 
     In some embodiments, an anti-TfR antibody and a molecular payload (e.g., an oligonucleotide) is linked via a structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10, wherein m is any number from 0-10. In some embodiments, n is 3 and/or (e.g., and) m is 4. In some embodiments, X is NH (e.g., NH from an amine group of a lysine). In some embodiments, X is S and the antibody is linked via conjugation to a cysteine of the antibody. In some embodiments, X is O and the antibody is linked via conjugation to a hydroxyl group of a serine, threonine, or tyrosine of the antibody. 
     In some embodiments, the complex described herein has a structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is any number from 0-10, wherein m is any number from 0-10. In some embodiments, n is 3 and/or (e.g., and) m is 4. 
     In structures formula (A), (B), (C), and (D), L1 is, in some embodiments, a spacer that is substituted or unsubstituted aliphatic, substituted or unsubstituted heteroaliphatic, substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, —O—, —N(R A )—, —S—, —C(═O)—, —C(═O)O—, —C(═O)NR A —, —NR A C(═O)—, —NR A C(═O)R A —, —C(═O)R A —, —NR A C(═O)O—, —NR A C(═O)N(R A )—, —OC(═O)—, —OC(═O)O—, —OC(═O)N(R A )—, —S(O) 2 NR A —, —NR A S(O) 2 —, or a combination thereof, wherein each R A  is independently hydrogen or substituted or unsubstituted alkyl. In some embodiments, L1 is 
     
       
         
         
             
             
         
       
     
     wherein the piperazine moiety links to the oligonucleotide, wherein L2 is 
     
       
         
         
             
             
         
       
     
     In some embodiments, L1 is: 
     
       
         
         
             
             
         
       
     
     wherein the piperazine links to the oligonucleotide. 
     In some embodiments, L1 is linked to the 5′ phosphate of the oligonucleotide. In some embodiments, L1 is linked to the 5′ phosphorothioate of the oligonucleotide. In some embodiments, L1 is linked to the 5′ phosphonoamidate of the oligonucleotide. 
     In some embodiments, L1 is optional (e.g., need not be present). 
     D. Examples of Antibody-Molecular Payload Complexes 
     Other aspects of the present disclosure provide complexes comprising any one the muscle targeting agent (e.g., a transferrin receptor antibodies) described herein covalently linked to any of the molecular payloads (e.g., an oligonucleotide) described herein. In some embodiments, the muscle targeting agent (e.g., a transferrin receptor antibody) is covalently linked to a molecular payload (e.g., an oligonucleotide) via a linker. Any of the linkers described herein may be used. In some embodiments, the linker is linked to the 5′ end, the 3′ end, or internally of the oligonucleotide. In some embodiments, the linker is linked to the antibody via a thiol-reactive linkage (e.g., via a cysteine in the antibody). In some embodiments, the linker (e.g., a Val-cit linker) is linked to the antibody (e.g., an anti-TfR antibody described herein) via a n amine group (e.g., via a lysine in the antibody). 
     An example of a structure of a complex comprising a transferrin receptor antibody covalently linked to an oligonucleotide via a Val-cit linker is provided below: 
     
       
         
         
             
             
         
       
     
     wherein the linker is linked to the 5′ end, the 3′ end, or internally of the oligonucleotide, and wherein the linker is linked to the antibody via a thiol-reactive linkage (e.g., via a cysteine in the antibody). 
     Another example of a structure of a complex comprising an anti-TfR antibody covalently linked to a molecular payload via a Val-cit linker is provided below: 
     
       
         
         
             
             
         
       
     
     wherein n is a number between 0-10, wherein m is a number between 0-10, wherein the linker is linked to the antibody via an amine group (e.g., on a lysine residue), and/or (e.g., and) wherein the linker is linked to the oligonucleotide (e.g., at the 5′ end, 3′ end, or internally). In some embodiments, the linker is linked to the antibody via a lysine, the linker is linked to the oligonucleotide at the 5′ end, n is 3, and m is 4. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, L1 is 
     
       
         
         
             
             
         
       
     
     It should be appreciated that antibodies can be linked to oligonucleotides with different stoichiometries, a property that may be referred to as a drug to antibody ratios (DAR) with the “drug” being the oligonucleotide. In some embodiments, one oligonucleotide is linked to an antibody (DAR=1). In some embodiments, two oligonucleotides are linked to an antibody (DAR=2). In some embodiments, three oligonucleotides are linked to an antibody (DAR=3). In some embodiments, four oligonucleotides are linked to an antibody (DAR=4). In some embodiments, a mixture of different complexes, each having a different DAR, is provided. In some embodiments, an average DAR of complexes in such a mixture may be in a range of 1 to 3, 1 to 4, 1 to 5 or more. DAR may be increased by conjugating oligonucleotides to different sites on an antibody and/or (e.g., and) by conjugating multimers to one or more sites on antibody. For example, a DAR of 2 may be achieved by conjugating a single oligonucleotide to two different sites on an antibody or by conjugating a dimer oligonucleotide to a single site of an antibody. 
     In some embodiments, the complex described herein comprises a transferrin receptor antibody (e.g., an antibody or any variant thereof as described herein) covalently linked to an oligonucleotide. In some embodiments, the complex described herein comprises a transferrin receptor antibody (e.g., an antibody or any variant thereof as described herein) covalently linked to an oligonucleotide via a linker (e.g., a Val-cit linker). In some embodiments, the linker (e.g., a Val-cit linker) is linked to the 5′ end, the 3′ end, or internally of the oligonucleotide. In some embodiments, the linker (e.g., a Val-cit linker) is linked to the antibody (e.g., an antibody or any variant thereof as described herein) via a thiol-reactive linkage (e.g., via a cysteine in the antibody). In some embodiments, the linker (e.g., a Val-cit linker) is linked to the antibody (e.g., an anti-TfR antibody described herein) via an amine group (e.g., via a lysine in the antibody). 
     In some embodiments, in any one of the examples of complexes described herein, the molecular payload is an oligonucleotide comprising a region of complementarity of at least 15 nucleotides to any one of the gene target sequences described herein, optionally wherein the target sequence is a sequence listed in Table 10. 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a CDR-H1, a CDR-H2, and a CDR-H3 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 2, Table 4, Table 7, or Table 9; and a CDR-L1, a CDR-L2, and a CDR-L3 that are the same as the CDR-L1, CDR-L2, and CDR-L3 shown in Table 2, Table 4, Table 7, or Table 9. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 1, a CDR-H2 of SEQ ID NO: 2, SEQ ID NO: 731, or SEQ ID NO: 80, a CDR-H3 of SEQ ID NO: 3, a CDR-L1 of SEQ ID NO: 4, a CDR-L2 of SEQ ID NO: 5, and a CDR-L3 of SEQ ID NO: 6; 
     (ii) a CDR-H1 of SEQ ID NO: 145, a CDR-H2 of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734, a CDR-H3 of SEQ ID NO: 147, a CDR-L1 of SEQ ID NO: 148, a CDR-L2 of SEQ ID NO: 149, and a CDR-L3 of SEQ ID NO: 6; or 
     (iii) a CDR-H1 of SEQ ID NO: 150, a CDR-H2 of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740, a CDR-H3 of SEQ ID NO: 152, a CDR-L1 of SEQ ID NO: 153, a CDR-L2 of SEQ ID NO: 5, and a CDR-L3 of SEQ ID NO: 154. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 10, a CDR-H3 of SEQ ID NO: 11, a CDR-L1 of SEQ ID NO: 12, a CDR-L2 of SEQ ID NO: 13, and a CDR-L3 of SEQ ID NO: 14; 
     (ii) a CDR-H1 of SEQ ID NO: 155, a CDR-H2 of SEQ ID NO: 156, a CDR-H3 of SEQ ID NO: 157, a CDR-L1 of SEQ ID NO: 158, a CDR-L2 of SEQ ID NO: 159, and a CDR-L3 of SEQ ID NO: 14; or 
     (iii) a CDR-H1 of SEQ ID NO: 160, a CDR-H2 of SEQ ID NO: 161, a CDR-H3 of SEQ ID NO: 162, a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 13, and a CDR-L3 of SEQ ID NO: 164. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737, a CDR-H2 of SEQ ID NO: 18, a CDR-H3 of SEQ ID NO: 19, a CDR-L1 of SEQ ID NO: 20, a CDR-L2 of SEQ ID NO: 21, and a CDR-L3 of SEQ ID NO: 22; 
     (ii) a CDR-H1 of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738, a CDR-H2 of SEQ ID NO: 166, a CDR-H3 of SEQ ID NO: 167, a CDR-L1 of SEQ ID NO: 168, a CDR-L2 of SEQ ID NO: 169, and a CDR-L3 of SEQ ID NO: 22; or 
     (iii) a CDR-H1 of SEQ ID NO: 170, a CDR-H2 of SEQ ID NO: 171, a CDR-H3 of SEQ ID NO: 172, a CDR-L1 of SEQ ID NO: 173, a CDR-L2 of SEQ ID NO: 21, and a CDR-L3 of SEQ ID NO: 174. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 188, a CDR-H2 of SEQ ID NO: 189, a CDR-H3 of SEQ ID NO: 190, a CDR-L1 of SEQ ID NO: 191, a CDR-L2 of SEQ ID NO: 192, and a CDR-L3 of SEQ ID NO: 193; 
     (ii) a CDR-H1 of SEQ ID NO: 194, a CDR-H2 of SEQ ID NO: 195, a CDR-H3 of SEQ ID NO: 196, a CDR-L1 of SEQ ID NO: 197, a CDR-L2 of SEQ ID NO: 198, and a CDR-L3 of SEQ ID NO: 193; or 
     (iii) a CDR-H1 of SEQ ID NO: 199, a CDR-H2 of SEQ ID NO: 200, a CDR-H3 of SEQ ID NO: 201, a CDR-L1 of SEQ ID NO: 202, a CDR-L2 of SEQ ID NO: 192, and a CDR-L3 of SEQ ID NO: 203. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises VH as shown in Table 2 or Table 7; and a VL as shown in Table 2 or Table 7. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a VH having the amino acid sequence of SEQ ID NO: 7 and a VL having the amino acid sequence of SEQ ID NO: 8. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a VH having the amino acid sequence of SEQ ID NO: 15 and a VL having the amino acid sequence of SEQ ID NO: 16. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a VH having the amino acid sequence of SEQ ID NO: 23 and a VL having the amino acid sequence of SEQ ID NO: 24. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a VH having the amino acid sequence of SEQ ID NO: 204 and a VL having the amino acid sequence of SEQ ID NO: 205. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a heavy chain having the amino acid sequence of SEQ ID NO: 178, SEQ ID NO: 185, SEQ ID NO: 769, SEQ ID NO: 770, SEQ ID NO: 773, or SEQ ID NO: 774, and a light chain having the amino acid sequence of SEQ ID NO: 179. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide) wherein the anti-TfR antibody comprises a heavy chain having the amino acid sequence of SEQ ID NO: 180, SEQ ID NO: 186, and a light chain having the amino acid sequence of SEQ ID NO: 181. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a heavy chain having the amino acid sequence of SEQ ID NO: 182, SEQ ID NO: 187, SEQ ID NO: 771, SEQ ID NO: 772, SEQ ID NO: 775, or SEQ ID NO: 776, and a light chain having the amino acid sequence of SEQ ID NO: 183. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload (e.g., an oligonucleotide), wherein the anti-TfR antibody comprises a heavy chain having the amino acid sequence of SEQ ID NO: 210, SEQ ID NO: 211, SEQ ID NO: 213, or SEQ ID NO: 777, and a light chain having the amino acid sequence of SEQ ID NO: 212. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody is a humanized antibody that comprises a VH that contains human framework regions with the CDR-H1, CDR-H2, and CDR-H3 of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12), and a VL that contains human framework regions with the CDR-L1, CDR-L2, and CDR-L3 of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody comprises a VH that contains human framework regions with the CDR-H1, CDR-H2, and CDR-H3 of a VH as set forth in SEQ ID NO: 7, and a VL that contains human framework regions with the CDR-L1, CDR-L2, and CDR-L3 of a VL as forth in SEQ ID NO: 8. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody comprises a VH that contains human framework regions with the CDR-H1, CDR-H2, and CDR-H3 of a VH as set forth in SEQ ID NO: 15, and a VL that contains human framework regions with the CDR-L1, CDR-L2, and CDR-L3 of a VL as forth in SEQ ID NO: 16. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody comprises a VH that contains human framework regions with the CDR-H1, CDR-H2, and CDR-H3 of a VH as set forth in SEQ ID NO: 23, and a VL that contains human framework regions with the CDR-L1, CDR-L2, and CDR-L3 of a VL as forth in SEQ ID NO: 24. In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody is an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody is a Fab′ fragment of an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked to a molecular payload, wherein the antibody is a Fab′ fragment of an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12). In some embodiments, the molecular payload is a DMPK-targeting oligonucleotide (e.g., a DMPK-targeting oligonucleotide listed in Table 10 and Table 16, or a DMPK targeting oligonucleotide targeting a target sequence listed in Table 10). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked via a lysine to the 5′ end of an oligonucleotide, wherein the antibody is a Fab′ fragment of an IgG1 kappa that comprises human framework regions with the CDRs of a murine antibody listed in Table 2 or Table 4 (e.g., 3A4, 3M12, or 5H12), wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked via a lysine to the 5′ end of an oligonucleotide, wherein the antibody is a Fab′ fragment of an IgG1 kappa that comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 777 and a light chain comprising the amino acid sequence of SEQ ID NO: 212, wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR antibody covalently linked via a lysine to the 5′ end of an oligonucleotide, wherein the antibody is a Fab′ fragment of an IgG1 kappa that comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 213 and a light chain comprising the amino acid sequence of SEQ ID NO: 212, wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 1, a CDR-H2 as set forth in SEQ ID NO: 2, a CDR-H3 as set forth in SEQ ID NO: 3, a CDR-L1 as set forth in SEQ ID NO: 4, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEQ ID NO: 6: wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 1, a CDR-H2 as set forth in SEQ ID NO: 731, a CDR-H3 as set forth in SEQ ID NO: 3, a CDR-L1 as set forth in SEQ ID NO: 4, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEQ ID NO: 6; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 1, a CDR-H2 as set forth in SEQ ID NO: 80, a CDR-H3 as set forth in SEQ ID NO: 3, a CDR-L1 as set forth in SEQ ID NO: 4, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEQ ID NO: 6: wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 145, a CDR-H2 as set forth in SEQ ID NO: 146, a CDR-H3 as set forth in SEQ ID NO: 147, a CDR-L1 as set forth in SEQ ID NO: 148, a CDR-L2 as set forth in SEQ ID NO: 149, and a CDR-L3 as set forth in SEQ ID NO: 6; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 145, a CDR-H2 as set forth in SEQ ID NO: 732, a CDR-H3 as set forth in SEQ ID NO: 147, a CDR-L1 as set forth in SEQ ID NO: 148, a CDR-L2 as set forth in SEQ ID NO: 149, and a CDR-L3 as set forth in SEQ ID NO: 6; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 145, a CDR-H2 as set forth in SEQ ID NO: 734, a CDR-H3 as set forth in SEQ ID NO: 147, a CDR-L1 as set forth in SEQ ID NO: 148, a CDR-L2 as set forth in SEQ ID NO: 149, and a CDR-L3 as set forth in SEQ ID NO: 6; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 150, a CDR-H2 as set forth in SEQ ID NO: 151, a CDR-H3 as set forth in SEQ ID NO: 152, a CDR-L1 as set forth in SEQ ID NO: 153, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEQ ID NO: 154; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 150, a CDR-H2 as set forth in SEQ ID NO: 739, a CDR-H3 as set forth in SEQ ID NO: 152, a CDR-L1 as set forth in SEQ ID NO: 153, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEQ ID NO: 154; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 150, a CDR-H2 as set forth in SEQ ID NO: 740, a CDR-H3 as set forth in SEQ ID NO: 152, a CDR-L1 as set forth in SEQ ID NO: 153, a CDR-L2 as set forth in SEQ ID NO: 5, and a CDR-L3 as set forth in SEO ID NO: 154: wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 9, a CDR-H2 as set forth in SEQ ID NO: 10, a CDR-H3 as set forth in SEQ ID NO: 11, a CDR-L1 as set forth in SEQ ID NO: 12, a CDR-L2 as set forth in SEQ ID NO: 13, and a CDR-L3 as set forth in SEO ID NO: 14: wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 155, a CDR-H2 as set forth in SEQ ID NO: 156, a CDR-H3 as set forth in SEQ ID NO: 157, a CDR-L1 as set forth in SEQ ID NO: 158, a CDR-L2 as set forth in SEQ ID NO: 159, and a CDR-L3 as set forth in SEQ ID NO: 14; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 160, a CDR-H2 as set forth in SEQ ID NO: 161, a CDR-H3 as set forth in SEQ ID NO: 162, a CDR-L1 as set forth in SEQ ID NO: 163, a CDR-L2 as set forth in SEQ ID NO: 13, and a CDR-L3 as set forth in SEQ ID NO: 164; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 17, a CDR-H2 as set forth in SEQ ID NO: 18, a CDR-H3 as set forth in SEQ ID NO: 19, a CDR-L1 as set forth in SEQ ID NO: 20, a CDR-L2 as set forth in SEQ ID NO: 21, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 735, a CDR-H2 as set forth in SEQ ID NO: 18, a CDR-H3 as set forth in SEQ ID NO: 19, a CDR-L1 as set forth in SEQ ID NO: 20, a CDR-L2 as set forth in SEQ ID NO: 21, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 737, a CDR-H2 as set forth in SEQ ID NO: 18, a CDR-H3 as set forth in SEQ ID NO: 19, a CDR-L1 as set forth in SEQ ID NO: 20, a CDR-L2 as set forth in SEQ ID NO: 21, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 165, a CDR-H2 as set forth in SEQ ID NO: 166, a CDR-H3 as set forth in SEQ ID NO: 167, a CDR-L1 as set forth in SEQ ID NO: 168, a CDR-L2 as set forth in SEQ ID NO: 169, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 736, a CDR-H2 as set forth in SEQ ID NO: 166, a CDR-H3 as set forth in SEQ ID NO: 167, a CDR-L1 as set forth in SEQ ID NO: 168, a CDR-L2 as set forth in SEQ ID NO: 169, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 738, a CDR-H2 as set forth in SEQ ID NO: 166, a CDR-H3 as set forth in SEQ ID NO: 167, a CDR-L1 as set forth in SEQ ID NO: 168, a CDR-L2 as set forth in SEQ ID NO: 169, and a CDR-L3 as set forth in SEQ ID NO: 22; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 170, a CDR-H2 as set forth in SEQ ID NO: 171, a CDR-H3 as set forth in SEQ ID NO: 172, a CDR-L1 as set forth in SEQ ID NO: 173, a CDR-L2 as set forth in SEQ ID NO: 21, and a CDR-L3 as set forth in SEQ ID NO: 174; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 188, a CDR-H2 as set forth in SEQ ID NO: 189, a CDR-H3 as set forth in SEQ ID NO: 190, a CDR-L1 as set forth in SEQ ID NO: 191, a CDR-L2 as set forth in SEQ ID NO: 192, and a CDR-L3 as set forth in SEQ ID NO: 193; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 194, a CDR-H2 as set forth in SEQ ID NO: 195, a CDR-H3 as set forth in SEQ ID NO: 196, a CDR-L1 as set forth in SEQ ID NO: 197, a CDR-L2 as set forth in SEQ ID NO: 198, and a CDR-L3 as set forth in SEQ ID NO: 193; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, the complex described herein comprises an anti-TfR Fab covalently linked via a lysine to the 5′ end of an oligonucleotide (e.g., a DMPK-targeting oligonucleotide), wherein the anti-TfR Fab comprises a CDR-H1 as set forth in SEQ ID NO: 199, a CDR-H2 as set forth in SEQ ID NO: 200, a CDR-H3 as set forth in SEQ ID NO: 201, a CDR-L1 as set forth in SEQ ID NO: 202, a CDR-L2 as set forth in SEQ ID NO: 192, and a CDR-L3 as set forth in SEQ ID NO: 203; wherein the complex has the structure of: 
     
       
         
         
             
             
         
       
     
     wherein n is 3 and m is 4 and wherein L1 is 
     
       
         
         
             
             
         
       
     
     optionally wherein the DMPK targeting oligonucleotide comprises a region of complementarity of at least 16 nucleotides to a target sequence as set forth in any one of SEQ ID NO: 482-717 and 2329-3861, further optionally wherein the DMPK targeting oligonucleotide (e.g., a gapmer) comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 consecutive nucleotides) of the nucleotide sequence of any one of SEQ ID NOs: 246-481 and 778-795 (e.g., any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362). 
     In some embodiments, in any one of the examples of complexes, L1 is linked to the 5′ phosphate of the oligonucleotide. In some embodiments, L1 is linked to the 5′ phosphorothioate of the oligonucleotide. In some embodiments, L1 is linked to the 5′ phosphonoamidate of the oligonucleotide. 
     In some embodiments, L1 is optional (e.g., need not be present). 
     III. Formulations 
     Complexes provided herein may be formulated in any suitable manner. Generally, complexes provided herein are formulated in a manner suitable for pharmaceutical use. For example, complexes can be delivered to a subject using a formulation that minimizes degradation, facilitates delivery and/or (e.g., and) uptake, or provides another beneficial property to the complexes in the formulation. In some embodiments, provided herein are compositions comprising complexes and pharmaceutically acceptable carriers. Such compositions can be suitably formulated such that when administered to a subject, either into the immediate environment of a target cell or systemically, a sufficient amount of the complexes enter target muscle cells. In some embodiments, complexes are formulated in buffer solutions such as phosphate-buffered saline solutions, liposomes, micellar structures, and capsids. 
     It should be appreciated that, in some embodiments, compositions may include separately one or more components of complexes provided herein (e.g., muscle-targeting agents, linkers, molecular payloads, or precursor molecules of any one of them). 
     In some embodiments, complexes are formulated in water or in an aqueous solution (e.g., water with pH adjustments). In some embodiments, complexes are formulated in basic buffered aqueous solutions (e.g., PBS). In some embodiments, formulations as disclosed herein comprise an excipient. In some embodiments, an excipient confers to a composition improved stability, improved absorption, improved solubility and/or (e.g., and) therapeutic enhancement of the active ingredient. In some embodiments, an excipient is a buffering agent (e.g., sodium citrate, sodium phosphate, a tris base, or sodium hydroxide) or a vehicle (e.g., a buffered solution, petrolatum, dimethyl sulfoxide, or mineral oil). 
     In some embodiments, a complex or component thereof (e.g., oligonucleotide or antibody) is lyophilized for extending its shelf-life and then made into a solution before use (e.g., administration to a subject). Accordingly, an excipient in a composition comprising a complex, or component thereof, described herein may be a lyoprotectant (e.g., mannitol, lactose, polyethylene glycol, or polyvinyl pyrolidone), or a collapse temperature modifier (e.g., dextran, ficoll, or gelatin). 
     In some embodiments, a pharmaceutical composition is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral, e.g., intravenous, intradermal, subcutaneous, administration. Typically, the route of administration is intravenous or subcutaneous. 
     Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. In some embodiments, formulations include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, and sodium chloride in the composition. Sterile injectable solutions can be prepared by incorporating the complexes in a required amount in a selected solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. 
     In some embodiments, a composition may contain at least about 0.1% of the complex, or component thereof, or more, although the percentage of the active ingredient(s) may be between about 1% and about 80% or more of the weight or volume of the total composition. Factors such as solubility, bioavailability, biological half-life, route of administration, product shelf life, as well as other pharmacological considerations will be contemplated by one skilled in the art of preparing such pharmaceutical formulations, and as such, a variety of dosages and treatment regimens may be desirable. 
     IV. Methods of Use/Treatment 
     Complexes comprising a muscle-targeting agent covalently linked to a molecular payload as described herein are effective in treating myotonic dystrophy. In some embodiments, complexes are effective in treating myotonic dystrophy type 1 (DM1). In some embodiments, DM1 is associated with an expansion of a CTG trinucleotide repeat in the 3′ non-coding region of DMPK. In some embodiments, the nucleotide expansions lead to toxic RNA repeats capable of forming hairpin structures that bind critical intracellular proteins, e.g., muscleblind-like proteins, with high affinity. 
     In some embodiments, a subject may be a human subject, a non-human primate subject, a rodent subject, or any suitable mammalian subject. In some embodiments, a subject may have myotonic dystrophy. In some embodiments, a subject has a DMPK allele, which may optionally contain a disease-associated repeat. In some embodiments, a subject may have a DMPK allele with an expanded disease-associated-repeat that comprises about 2-10 repeat units, about 2-50 repeat units, about 2-100 repeat units, about 50-1,000 repeat units, about 50-500 repeat units, about 50-250 repeat units, about 50-100 repeat units, about 500-10,000 repeat units, about 500-5,000 repeat units, about 500-2,500 repeat units, about 500-1,000 repeat units, or about 1,000-10,000 repeat units. In some embodiments, a subject is suffering from symptoms of DM1, e.g. muscle atrophy or muscle loss. In some embodiments, a subject is not suffering from symptoms of DM1. In some embodiments, subjects have congenital myotonic dystrophy. 
     An aspect of the disclosure includes a method involving administering to a subject an effective amount of a complex as described herein. In some embodiments, an effective amount of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload can be administered to a subject in need of treatment. In some embodiments, a pharmaceutical composition comprising a complex as described herein may be administered by a suitable route, which may include intravenous administration, e.g., as a bolus or by continuous infusion over a period of time. In some embodiments, intravenous administration may be performed by intramuscular, intraperitoneal, intracerebrospinal, subcutaneous, intra-articular, intrasynovial, or intrathecal routes. In some embodiments, a pharmaceutical composition may be in solid form, aqueous form, or a liquid form. In some embodiments, an aqueous or liquid form may be nebulized or lyophilized. In some embodiments, a nebulized or lyophilized form may be reconstituted with an aqueous or liquid solution. 
     Compositions for intravenous administration may contain various carriers such as vegetable oils, dimethylactamide, dimethyformamide, ethyl lactate, ethyl carbonate, isopropyl myristate, ethanol, and polyols (glycerol, propylene glycol, liquid polyethylene glycol, and the like). For intravenous injection, water soluble antibodies can be administered by the drip method, whereby a pharmaceutical formulation containing the antibody and a physiologically acceptable excipients is infused. Physiologically acceptable excipients may include, for example, 5% dextrose, 0.9% saline, Ringer&#39;s solution or other suitable excipients. Intramuscular preparations, e.g., a sterile formulation of a suitable soluble salt form of the antibody, can be dissolved and administered in a pharmaceutical excipient such as Water-for-Injection, 0.9% saline, or 5% glucose solution. 
     In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload is administered via site-specific or local delivery techniques. Examples of these techniques include implantable depot sources of the complex, local delivery catheters, site specific carriers, direct injection, or direct application. 
     In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload is administered at an effective concentration that confers therapeutic effect on a subject. Effective amounts vary, as recognized by those skilled in the art, depending on the severity of the disease, unique characteristics of the subject being treated, e.g. age, physical conditions, health, or weight, the duration of the treatment, the nature of any concurrent therapies, the route of administration and related factors. These related factors are known to those in the art and may be addressed with no more than routine experimentation. In some embodiments, an effective concentration is the maximum dose that is considered to be safe for the patient. In some embodiments, an effective concentration will be the lowest possible concentration that provides maximum efficacy. 
     Empirical considerations, e.g. the half-life of the complex in a subject, generally will contribute to determination of the concentration of pharmaceutical composition that is used for treatment. The frequency of administration may be empirically determined and adjusted to maximize the efficacy of the treatment. 
     Generally, for administration of any of the complexes described herein, an initial candidate dosage may be about 1 to 100 mg/kg, or more, depending on the factors described above, e.g. safety or efficacy. In some embodiments, a treatment will be administered once. In some embodiments, a treatment will be administered daily, biweekly, weekly, bimonthly, monthly, or at any time interval that provide maximum efficacy while minimizing safety risks to the subject. Generally, the efficacy and the treatment and safety risks may be monitored throughout the course of treatment. 
     In some embodiments, an initial candidate dosage is about 1-50, 1-25, 1-10, 1-5, 5-100, 5-50, 5-25, 5-10, 10-100, 10-75, 10-50, 10-25, 10-20, 25-100, 25-75, or 25-50 mg/kg. In some embodiments, an initial candidate dosage is about 1-20, 1-15, 1-10, 1-5, 1-3, 1-2, 5-20, 5-15, or 5-10 mg/kg. In some embodiments, an initial candidate dosage is about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 mg/kg. 
     The efficacy of treatment may be assessed using any suitable methods. In some embodiments, the efficacy of treatment may be assessed by evaluation of observation of symptoms associated with DM1, e.g. muscle atrophy or muscle weakness, through measures of a subject&#39;s self-reported outcomes, e.g. mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, or by quality-of-life indicators, e.g. lifespan. 
     In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein is administered to a subject at an effective concentration sufficient to inhibit activity or expression of a target gene by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or at least 95% relative to a control, e.g. baseline level of gene expression prior to treatment. 
     In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject is sufficient to inhibit activity or expression of a target gene for at least 1-5, 1-10, 5-15, 10-20, 15-30, 20-40, 25-50, or more days. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject is sufficient to inhibit activity or expression of a target gene for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 20, or 24 weeks. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject is sufficient to inhibit activity or expression of a target gene for at least 1-5, 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-15, 10-12, 10-15, 10-20, 12-15, 12-20, 15-20, or 15-25 weeks. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject is sufficient to inhibit activity or expression of a target gene for at least 1, 2, 3, 4, 5, or 6 months. 
     In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject persists or remains in the subject for at least 1-5, 1-10, 5-15, 10-20, 15-30, 20-40, 25-50, or more days. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject persists or remains in the subject for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 20, or 24 weeks. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject persists or remains in the subject for at least 1-5, 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-15, 10-12, 10-15, 10-20, 12-15, 12-20, 15-20, or 15-25 weeks. In some embodiments, a single dose or administration of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein to a subject persists or remains in the subject for at least 1, 2, 3, 4, 5, or 6 months. 
     In some embodiments, multiple doses or administrations of a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein are delivered to a subject. In some embodiments, multiple doses of a pharmaceutical composition comprise delivering 2, 3, 4, 5, 6, 7, 8, 9, or 10 doses to a subject. In some embodiments, multiple doses of a pharmaceutical composition comprise delivering a dose to a subject every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 weeks. In some embodiments, multiple doses of a pharmaceutical composition comprise delivering a dose to a subject once every 4 weeks. In some embodiments, multiple doses of a pharmaceutical composition comprise delivering a dose to a subject once every 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-16, 10-12, 10-15, 10-20, 12-15, 12-20, 15-20, or 15-25 weeks. In some embodiments, multiple doses of a pharmaceutical composition comprise delivering a dose to a subject on a biweekly (i.e., every two weeks), bimonthly (i.e., every two months), or quarterly schedule (i.e., every twelve weeks). 
     In some embodiments, a single dose or administration is about 1-50, 1-25, 1-10, 1-15, 1-5, 5-100, 5-50, 5-25, 5-10, 10-100, 10-75, 10-50, 10-25, 10-20, 25-100, 25-75, or 25-50 mg/kg. In some embodiments, a single dose or administration is about 1-20, 1-15, 1-10, 1-5, 1-3, 1-2, 5-20, 5-15, or 5-10 mg/kg. In some embodiments, a single dose or administration is about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 20 mg/kg. 
     In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein is delivered to a subject every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 weeks. In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein is delivered to a subject every 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-16, 9-15, 10-12, 10-14, 10-15, 10-20, 11-13, 11-15, 12-15, 12-16, 12-20, 15-20, or 15-25 weeks. In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein is delivered to a subject on a biweekly (i.e., every two weeks), bimonthly (i.e., every two months), or quarterly schedule (i.e., every twelve weeks). 
     In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein at a concentration of 1-15 mg/kg of RNA is delivered to a subject every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 weeks. In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein at a concentration of 1-15 mg/kg of RNA is delivered to a subject every 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-16, 9-15, 10-12, 10-14, 10-15, 10-20, 11-13, 11-15, 12-15, 12-16, 12-20, 15-20, or 15-25 weeks. In some embodiments, a pharmaceutical composition that comprises a complex comprising a muscle-targeting agent covalently linked to a molecular payload described herein at a concentration of 1-15 mg/kg of RNA is delivered to a subject on a biweekly (i.e., every two weeks), bimonthly (i.e., every two months), or quarterly schedule (i.e., every twelve weeks). 
     In some embodiments, a pharmaceutical composition may comprises more than one complex comprising a muscle-targeting agent covalently linked to a molecular payload. In some embodiments, a pharmaceutical composition may further comprise any other suitable therapeutic agent for treatment of a subject, e.g. a human subject having DM1. In some embodiments, the other therapeutic agents may enhance or supplement the effectiveness of the complexes described herein. In some embodiments, the other therapeutic agents may function to treat a different symptom or disease than the complexes described herein. 
     EXAMPLES 
     Example 1: Targeting DMPK with Transfected Antisense Oligonucleotides 
     A gapmer antisense oligonucleotide that targets both wild-type and mutant alleles of DMPK (control DMPK-ASO) was tested in vitro for its ability to reduce expression levels of DMPK in an immortalized cell line. Briefly, Hepa 1-6 cells were transfected with the control DMPK-ASO (100 nM) formulated with lipofectamine 2000. DMPK expression levels were evaluated 72 hours following transfection. A control experiment was also performed in which vehicle (phosphate-buffered saline) was delivered to Hepa 1-6 cells in culture and the cells were maintained for 72 hours. As shown in  FIG.  1   , it was found that the control DMPK-ASO reduced DMPK expression levels by ˜90% compared with controls. 
     Example 2: Targeting DMPK with a Muscle-Targeting Complex 
     A muscle-targeting complex was generated comprising the DMPK ASO used in Example 1 (control DMPK-ASO) covalently linked, via a cathepsin cleavable linker, to DTX-A-002 (RI7 217 (Fab)), an anti-transferrin receptor antibody. 
     Briefly, a maleimidocaproyl-L-valine-L-citrulline-p-aminobenzyl alcohol p-nitrophenyl carbonate (MC-Val-Cit-PABC-PNP) linker molecule was coupled to NH 2 -C 6 -control DMPK-ASO using an amide coupling reaction. Excess linker and organic solvents were removed by gel permeation chromatography. The purified Val-Cit-linker-control DMPK-ASO was then coupled to a thiol-reactive anti-transferrin receptor antibody (DTX-A-002). 
     The product of the antibody coupling reaction was then subjected to hydrophobic interaction chromatography (HIC-HPLC).  FIG.  2 A  shows a resulting HIC-HPLC chromatogram, in which fractions B7-C2 of the chromatogram (denoted by vertical lines) contained antibody-oligonucleotide complexes (referred to as DTX-C-008) comprising one or two DMPK ASO molecules covalently attached to DTX-A-002, as determined by SDS-PAGE. These HIC-HPLC fractions were combined and densitometry confirmed that this sample of DTX-C-008 complexes had an average ASO to antibody ratio of 1.48. SDS-PAGE analysis demonstrated that 86.4% of this sample of DTX-C-008 complexes comprised DTX-A-002 linked to either one or two DMPK ASO molecules ( FIG.  2 B ). 
     Using the same methods as described above, a control complex was generated comprising the DMPK ASO used in Example 1 (control DMPK-ASO) covalently linked via a Val-Cit linker to an IgG2a (Fab) antibody (DTX-C-007). 
     The purified DTX-C-008 was then tested for cellular internalization and inhibition of DMPK. Hepa 1-6 cells, which have relatively high expression levels of transferrin receptor, were incubated in the presence of vehicle control, DTX-C-008 (100 nM), or DTX-C-007 (100 nM) for 72 hours. After the 72 hour incubation, the cells were isolated and assayed for expression levels of DMPK ( FIG.  3   ). Cells treated with the DTX-C-008 demonstrated a reduction in DMPK expression by ˜65% relative to the cells treated with the vehicle control. Meanwhile, cells treated with the DTX-C-007 had DMPK expression levels comparable to the vehicle control (no reduction in DMPK expression). These data indicate that the anti-transferrin receptor antibody of the DTX-C-008 enabled cellular internalization of the complex, thereby allowing the DMPK ASO to inhibit expression of DMPK. 
     Example 3: Targeting DMPK in Mouse Muscle Tissues with a Muscle-Targeting Complex 
     The muscle-targeting complex described in Example 2, DTX-C-008, was tested for inhibition of DMPK in mouse tissues. C57BL/6 wild-type mice were intravenously injected with a single dose of a vehicle control, control DMPK-ASO (3 mg/kg of RNA), DTX-C-008 (3 mg/kg of RNA, corresponding to 20 mg/kg antibody conjugate), or DTX-C-007 (3 mg/kg of RNA, corresponding to 20 mg/kg antibody conjugate). Control DMPK-ASO, the DMPK ASO as described in Example 1, was used as a control. Each experimental condition was replicated in three individual C57BL/6 wild-type mice. Following a seven-day period after injection, the mice were euthanized and segmented into isolated tissue types. Individual tissue samples were subsequently assayed for expression levels of DMPK ( FIGS.  4 A- 4 E and  5 A- 5 B ). 
     Mice treated with the DTX-C-008 complex demonstrated a reduction in DMPK expression in a variety of skeletal, cardiac, and smooth muscle tissues. For example, as shown in  FIGS.  4 A- 4 E , DMPK expression levels were significantly reduced in gastrocnemius (50% reduction), heart (30% reduction), esophagus (45% reduction), tibialis anterior (47% reduction), and soleus (31% reduction) tissues, relative to the mice treated with the vehicle control. Meanwhile, mice treated with the DTX-C-007 complex had DMPK expression levels comparable to the vehicle control (no reduction in DMPK expression) for all assayed muscle tissue types. 
     Mice treated with the DTX-C-008 complex demonstrated no change in DMPK expression in non-muscle tissues such as spleen and brain tissues ( FIGS.  5 A and  5 B ). 
     These data indicate that the anti-transferrin receptor antibody of the DTX-C-008 enabled cellular internalization of the complex into muscle-specific tissues in an in vivo mouse model, thereby allowing the DMPK ASO to inhibit expression of DMPK. These data further demonstrate that the DTX-C-008 complex is capable of specifically targeting muscle tissues. 
     Example 4: Targeting DMPK in Mouse Muscle Tissues with a Muscle-Targeting Complex 
     The muscle-targeting complex described in Example 2, DTX-C-008, was tested for dose-dependent inhibition of DMPK in mouse tissues. C57BL/6 wild-type mice were intravenously injected with a single dose of a vehicle control (phosphate-buffered saline, PBS), control DMPK-ASO (10 mg/kg of RNA), DTX-C-008 (3 mg/kg or 10 mg/kg of RNA, wherein 3 mg/kg corresponds to 20 mg/kg antibody conjugate), or DTX-C-007 (3 mg/kg or 10 mg/kg of RNA, wherein 3 mg/kg corresponds to 20 mg/kg antibody conjugate). Control DMPK-ASO, the DMPK ASO as described in Example 1, was used as a control. Each experimental condition was replicated in five individual C57BL/6 wild-type mice. Following a seven-day period after injection, the mice were euthanized and segmented into isolated tissue types. Individual tissue samples were subsequently assayed for expression levels of DMPK ( FIGS.  6 A- 6 F ). 
     Mice treated with the DTX-C-008 complex demonstrated a reduction in DMPK expression in a variety of skeletal muscle tissues. As shown in  FIGS.  6 A- 6 F , DMPK expression levels were significantly reduced in tibialis anterior (58% and 75% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively), soleus (55% and 66% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively), extensor digitorum longus (EDL) (52% and 72% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively), gastrocnemius (55% and 77% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively), heart (19% and 35% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively), and diaphragm (53% and 70% reduction for 3 mg/kg and 10 mg/kg DTX-C-008, respectively) tissues, relative to the mice treated with the vehicle control. Notably, all assayed muscle tissue types experienced dose-dependent inhibition of DMPK, with greater reduction in DMPK levels at 10 mg/kg antibody conjugate relative to 3 mg/kg antibody conjugate. 
     Meanwhile, mice treated with the control DTX-C-007 complex had DMPK expression levels comparable to the vehicle control (no reduction in DMPK expression) for all assayed muscle tissue types. These data indicate that the anti-transferrin receptor antibody of the DTX-C-008 enabled cellular internalization of the complex into muscle-specific tissues in an in vivo mouse model, thereby allowing the DMPK ASO to inhibit expression of DMPK. These data further demonstrate that the DTX-C-008 complex is capable of specifically targeting muscle tissues for dose-dependent inhibition of DMPK. 
     Example 5: Targeting DMPK in Cynomolgus Monkey Muscle Tissues with a Muscle-Targeting Complex 
     A muscle-targeting complex comprising control DMPK-ASO (DTX-C-012), was generated and purified using methods described in Example 2. DTX-C-012 is a complex comprising a human anti-transferrin receptor antibody (a 15G11 antibody comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 240 and a light chain comprising the amino acid sequence of SEQ ID NO: 237) that binds to the human transferrin receptor and the cynomolgus monkey transferrin receptor, covalently linked, via a cathepsin cleavable Val-Cit linker, to control DMPK-ASO, an antisense oligonucleotide that targets DMPK. Following HIC-HPLC purification, densitometry confirmed that DTX-C-012 had an average ASO to antibody ratio of 1.32, and SDS-PAGE revealed a purity of 92.3%. 
     DTX-C-012 was tested for dose-dependent inhibition of DMPK in male cynomolgus monkey tissues. Male cynomolgus monkeys (19-31 months; 2-3 kg) were intravenously injected with a single dose of a saline control, control DMPK-ASO (naked DMPK ASO) (10 mg/kg of RNA), or DTX-C-012 (10 mg/kg of RNA) on Day 0. Each experimental condition was replicated in three individual male cynomolgus monkeys. On Day 7 after injection, tissue biopsies (including muscle tissues) were collected. DMPK mRNA expression levels, ASO detection assays, serum clinical chemistries, tissue histology, clinical observations, and body weights were analyzed. The monkeys were euthanized on Day 14. 
     Significant knockdown (KD) of DMPK mRNA expression using DTX-C-012 was observed in soleus, deep flexor, and masseter muscles relative to saline control, with 39% KD, 62% KD, and 41% KD, respectively ( FIGS.  7 A- 7 C ). Robust knockdown of DMPK mRNA expression DTX-C-012 was further observed in gastrocnemius (62% KD;  FIG.  7 D ), EDL (29% KD;  FIG.  7 E ), tibialis anterior muscle (23% KD;  FIG.  7 F ), diaphragm (54% KD;  FIG.  7 G ), tongue (43% KD;  FIG.  7 H ), heart muscle (36% KD;  FIG.  7 I ), quadriceps (58% KD;  FIG.  7 J ), bicep (51% KD;  FIG.  7 K ), and deltoid muscles (47% KD;  FIG.  7 L ). Knockdown of DMPK mRNA expression DTX-C-012 in smooth muscle was also observed in the intestine, with 63% KD at jejunum-duodenum ends ( FIG.  8 A ) and 70% KD in ileum ( FIG.  8 B ). Notably, naked DMPK ASO (i.e., not linked to a muscle-targeting agent), control DMPK-ASO, had minimal effects on DMPK expression levels relative to the vehicle control (i.e., little or no reduction in DMPK expression) for all assayed muscle tissue types. Monkeys treated with the DTX-C-012 complex demonstrated no change in DMPK expression in non-muscle tissues, such as liver, kidney, brain, and spleen tissues ( FIGS.  9 A- 9 D ). Additional tissues were examined, as depicted in  FIG.  10   , which shows normalized DMPK mRNA tissue expression levels across several tissue types in cynomolgus monkeys. (N=3 male cynomolgus monkeys) 
     Prior to euthanization, all monkeys were tested for reticulocyte levels, platelet levels, hemoglobin expression, alanine aminotransferase (ALT) expression, aspartate aminotransferase (AST) expression, and blood urea nitrogen (BUN) levels on days 2, 7, and 14 after dosing. As shown in  FIG.  12   , monkeys dosed with antibody-oligonucleotide complex had normal reticulocyte levels, platelet levels, hemoglobin expression, alanine aminotransferase (ALT) expression, aspartate aminotransferase (AST) expression, and blood urea nitrogen (BUN) levels throughout the length of the experiment. These data show that a single dose of a complex comprising control DMPK-ASO is safe and tolerated in cynomolgus monkeys. 
     These data demonstrate that the 15G11 antibody of the DTX-C-012 complex enabled cellular internalization of the complex into muscle-specific tissues in an in vivo cynomolgus monkey model, thereby allowing the DMPK ASO (control DMPK-ASO) to inhibit expression of DMPK. These data further demonstrate that the DTX-C-012 complex is capable of specifically targeting muscle tissues for dose-dependent inhibition of DMPK without substantially impacting non-muscle tissues. This is direct contrast with the limited ability of control DMPK-ASO, a naked DMPK ASO (not linked to a muscle-targeting agent), to inhibit expression of DMPK in muscle tissues of an in vivo cynomolgus monkey model. 
     Example 6: Targeting DMPK in Mouse Muscle Tissues with a Muscle-Targeting Complex 
     The muscle-targeting complex described in Example 2, DTX-C-008, was tested for time-dependent inhibition of DMPK in mouse tissues. C57BL/6 wild-type mice were intravenously injected with a single dose of a vehicle control (saline), control DMPK-ASO (10 mg/kg of RNA), or DTX-C-008 (10 mg/kg of RNA) and euthanized after a prescribed period of time, as described in Table 1. Following euthanization, the mice were segmented into isolated tissue types and tissue samples were subsequently assayed for expression levels of DMPK ( FIGS.  11 A- 11 B ). 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Experimental conditions 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Days after injection 
                 Number of 
               
               
                 Group 
                 Dosage 
                 before euthanization 
                 mice 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 Vehicle (saline) 
                 3 
                 days 
                 3 
               
               
                 2 
                 Vehicle (saline) 
                 7 
                 days 
                 3 
               
               
                 3 
                 Vehicle (saline) 
                 14 
                 days 
                 3 
               
               
                 4 
                 Vehicle (saline) 
                 28 
                 days 
                 3 
               
               
                 5 
                 control DMPK- 
                 3 
                 days 
                 3 
               
               
                   
                 ASO 
               
               
                 6 
                 control DMPK- 
                 7 
                 days 
                 3 
               
               
                   
                 ASO 
               
               
                 7 
                 control DMPK- 
                 14 
                 days 
                 3 
               
               
                   
                 ASO 
               
               
                 8 
                 control DMPK- 
                 28 
                 days 
                 3 
               
               
                   
                 ASO 
               
               
                 9 
                 DTX-C-008 
                 3 
                 days 
                 3 
               
               
                 10 
                 DTX-C-008 
                 7 
                 days 
                 3 
               
               
                 11 
                 DTX-C-008 
                 14 
                 days 
                 3 
               
               
                 12 
                 DTX-C-008 
                 28 
                 days 
                 3 
               
               
                   
               
            
           
         
       
     
     Mice treated with the DTX-C-008 complex demonstrated approximately 50% reduction in DMPK expression in gastrocnemius ( FIG.  11 A ) and tibialis anterior ( FIG.  11 B ) muscles for all of Groups 9-12 (3-28 days between injection and euthanization), relative to vehicle. Mice treated with the control DMPK-ASO naked oligonucleotide did not demonstrate significant reduction in DMPK expression. 
     These data indicate that the DTX-C-008 complex was capable of providing persistent reduction in DMPK expression for up to 28 days following dosage of mice with said DTX-C-008 complex. 
     Example 7: Evaluation of Antisense Oligonucleotides that Target DMPK in Immortalized Myoblasts 
     Two hundred and thirty-six oligonucleotides for targeting DMPK were generated using in silico analysis. Each individual oligonucleotide was evaluated for their ability to target DMPK in cellulo at two doses—0.5 nM (low dose) and 50 nM (high dose). 
     Briefly, DM1 C15 immortalized myoblasts were cultured in T-75 flasks until near confluency (˜80% confluent). Myoblasts were then disrupted with trypsin and seeded into 96-well microplates at a density of 50,000 cells/well. Cells were allowed to recover overnight before the growth media was washed out and replaced with a no-serum media to induce differentiation into myotubes. Differentiation proceeded for seven days prior to treatment with DMPK-targeting oligonucleotides. 
     On day seven following induction of differentiation, DM1 C15 myotubes were transfected with an individual oligonucleotide using 0.3 μL of Lipofectamine MessengerMax per well. All oligonucleotides were tested at both 0.5 nM and 50 nM final concentrations in biological triplicates. After treatment with oligonucleotides, cells were incubated for 72 hours prior to being harvested for total RNA. cDNA was synthesized from the total RNA extracts and qPCR was performed to determine expression levels of DMPK in technical quadruplicate. All qPCR data were analyzed using a traditional MET method and were normalized to a plate-based negative control that comprised cells treated with vehicle control (0.3 μL/well Lipofectamine MessengerMax without any oligonucleotide). Results from these experiments are shown in Table 10. ‘Normalized DMPK Remaining’ for each antisense oligonucleotide in Table 10 refers to the expression level of DMPK in cell treated with said antisense oligonucleotide relative to the negative control that comprised cells treated with vehicle control (wherein the expression level of the negative control has been normalized to equal 1.00) 
     The majority of tested DMPK-targeting antisense oligonucleotides demonstrated a reduction in DMPK expression in differentiated myotubes at both the low and high dose concentrations (0.5 nM and 50 nM, respectively). These data demonstrate that the antisense oligonucleotides shown in Table 10 are capable of targeting DMPK in cellulo, suggesting that muscle-targeting complexes comprising these antisense oligonucleotides would be capable of targeting DMPK in muscle tissues in vivo. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Ability ofDMPK-targeting antisense oligonucleotides to reduce expression of 
               
               
                 DMPK in cellulo 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 0.5 nM 
                 50 nM 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Antisense 
                 SEQ 
                   
                 SEQ 
                 Normalized 
                 Percent 
                 Normalized 
                 Percent 
               
               
                 Oligonucleotide 
                 NO: 
                 DMPK Target 
                 NO: 
                 DMPK 
                 DMPK 
                 DMPK 
                 DMPK 
               
               
                 Sequence 
                 ID 
                 Sequence 
                 ID 
                 Remaining 
                 Reduction 
                 Remaining 
                 Reduction 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 GGACGGCCCGGC 
                 246 
                 GGCAGCAAGCCG 
                 482 
                 0.42 
                 58.25 
                 0.31 
                 69.30 
               
               
                 UUGCUGCC 
                   
                 GGCCGTCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGCCCGGAUCA 
                 247 
                 CAGTCCTGTGATC 
                 483 
                 0.42 
                 57.97 
                 0.38 
                 61.96 
               
               
                 CAGGACUG 
                   
                 CGGGCCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAAACUUGCUCA 
                 248 
                 GACACTGCTGAG 
                 484 
                 0.69 
                 31.45 
                 0.46 
                 53.93 
               
               
                 GCAGUGUC 
                   
                 CAAGTTTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAACUUGCUCAG 
                 249 
                 TGACACTGCTGA 
                 485 
                 0.69 
                 30.85 
                 0.49 
                 50.69 
               
               
                 CAGUGUCA 
                   
                 GCAAGTTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGAUGGCCUCC 
                 250 
                 CGGGAGATGGAG 
                 486 
                 0.71 
                 28.92 
                 0.44 
                 55.57 
               
               
                 AUCUCCCG 
                   
                 GCCATCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCGGCCGGAAU 
                 251 
                 GGGAGCGGATTC 
                 487 
                 0.71 
                 28.64 
                 0.35 
                 64.75 
               
               
                 CCGCUCCC 
                   
                 CGGCCGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUCGGCCGGAA 
                 252 
                 GGAGCGGATTCC 
                 488 
                 0.72 
                 27.88 
                 0.33 
                 67.46 
               
               
                 UCCGCUCC 
                   
                 GGCCGAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCUCAGCAGUG 
                 253 
                 CCTGCTGACACTG 
                 489 
                 0.73 
                 27.08 
                 0.34 
                 65.78 
               
               
                 UCAGCAGG 
                   
                 CTGAGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGUCGGGUUUG 
                 254 
                 AGGGACATCAAA 
                 490 
                 0.66 
                 34.16 
                 0.44 
                 55.56 
               
               
                 AUGUCCCU 
                   
                 CCCGACAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUUGCGGGUUUG 
                 255 
                 GGGACATCAAAC 
                 491 
                 0.67 
                 33.31 
                 0.39 
                 61.07 
               
               
                 AUGUCCC 
                   
                 CCGACAAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCCGCCAGGUAG 
                 256 
                 GCGCGCTTCTACC 
                 492 
                 0.72 
                 27.99 
                 0.20 
                 80.06 
               
               
                 AAGCGCGC 
                   
                 TGGCGGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUGGCAUACAC 
                 257 
                 CGGGCCAGGTGT 
                 493 
                 0.68 
                 31.63 
                 0.26 
                 74.03 
               
               
                 CUGGCCCG 
                   
                 ATGCCATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AACUUGCUCAGC 
                 258 
                 CTGACACTGCTG 
                 494 
                 0.80 
                 19.81 
                 0.47 
                 52.64 
               
               
                 AGUGUCAG 
                   
                 AGCAAGTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGCUGCGUGAU 
                 259 
                 GGCGGTGGATCA 
                 495 
                 0.81 
                 19.03 
                 0.32 
                 68.34 
               
               
                 CCACCGCC 
                   
                 CGCAGCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGAAUGUCCGAC 
                 260 
                 GAGACACTGTCG 
                 496 
                 0.60 
                 40.21 
                 0.36 
                 64.42 
               
               
                 AGUGUCUC 
                   
                 GACATTCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAAGUCGGCCAG 
                 261 
                 ACATCCGCCTGG 
                 497 
                 0.82 
                 18.36 
                 0.56 
                 44.04 
               
               
                 GCGGAUGU 
                   
                 CCGACTTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGUCGGGUUUGA 
                 262 
                 CAGGGACATCAA 
                 498 
                 0.70 
                 30.09 
                 0.32 
                 68.14 
               
               
                 UGUCCCUG 
                   
                 ACCCGACA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGAUGGCCUCCA 
                 263 
                 CCGGGAGATGGA 
                 499 
                 0.75 
                 24.93 
                 0.39 
                 60.77 
               
               
                 UCUCCCGG 
                   
                 GGCCATCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGAUGUUGUCG 
                 264 
                 ATCAAACCCGAC 
                 500 
                 0.76 
                 24.19 
                 0.61 
                 39.48 
               
               
                 GGUUUGAU 
                   
                 AACATCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUCGGGUUUGAU 
                 265 
                 ACAGGGACATCA 
                 501 
                 0.71 
                 28.89 
                 0.36 
                 64.15 
               
               
                 GUCCCUGU 
                   
                 AACCCGAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAUACUCCAUGA 
                 266 
                 GTACCTGGTCATG 
                 502 
                 0.71 
                 28.86 
                 0.48 
                 52.07 
               
               
                 CCAGGUAC 
                   
                 GAGTATT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUUGUUCAUGAU 
                 267 
                 CCATGAAGATCA 
                 503 
                 0.84 
                 16.06 
                 0.51 
                 49.47 
               
               
                 CUUCAUGG 
                   
                 TGAACAAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCAGUGCAUCCA 
                 268 
                 CCACGTTTTGGAT 
                 504 
                 0.84 
                 15.76 
                 0.58 
                 42.06 
               
               
                 AAACGUGG 
                   
                 GCACTGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUGUCCCGGAGA 
                 269 
                 TGGGATGGTCTCC 
                 505 
                 0.64 
                 35.85 
                 0.49 
                 50.78 
               
               
                 CCAUCCCA 
                   
                 GGGACAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGCCUGGGACC 
                 270 
                 GACAGTGAGGTC 
                 506 
                 0.63 
                 37.19 
                 0.23 
                 76.81 
               
               
                 UCACUGUC 
                   
                 CCAGGCCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCCACGUAAUAC 
                 271 
                 GTCATGGAGTATT 
                 507 
                 0.72 
                 28.21 
                 0.54 
                 45.94 
               
               
                 UCCAUGAC 
                   
                 ACGTGGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCUGCCGCAGG 
                 272 
                 CGGCTGTCCCTGC 
                 508 
                 0.63 
                 37.09 
                 0.06 
                 93.59 
               
               
                 GACAGCCG 
                   
                 GGCAGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUGUGCACGUAG 
                 273 
                 CGGCTTGGCTAC 
                 509 
                 0.74 
                 25.67 
                 0.30 
                 70.10 
               
               
                 CCAAGCCG 
                   
                 GTGCACAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCCCAUCCACG 
                 274 
                 GGCCCTGACGTG 
                 510 
                 0.86 
                 13.63 
                 0.67 
                 33.09 
               
               
                 UCAGGGCC 
                   
                 GATGGGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCGCCUCCGAU 
                 275 
                 CCTGGCCTATCGG 
                 511 
                 0.79 
                 21.19 
                 0.38 
                 61.91 
               
               
                 AGGCCAGG 
                   
                 AGGCGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGUGCACGUAGC 
                 276 
                 CCGGCTTGGCTAC 
                 512 
                 0.75 
                 24.74 
                 0.25 
                 75.09 
               
               
                 CAAGCCGG 
                   
                 GTGCACA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GACCAGGUACAG 
                 277 
                 AGAACTACCTGT 
                 513 
                 0.57 
                 42.85 
                 0.29 
                 70.95 
               
               
                 GUAGUUCU 
                   
                 ACCTGGTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAUCUCGGCCG 
                 278 
                 GCGGATTCCGGC 
                 514 
                 0.79 
                 20.50 
                 0.40 
                 59.76 
               
               
                 GAAUCCGC 
                   
                 CGAGATGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUCUCGGCCGG 
                 279 
                 AGCGGATTCCGG 
                 515 
                 0.80 
                 20.21 
                 0.41 
                 59.40 
               
               
                 AAUCCGCU 
                   
                 CCGAGATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGCCAUAGGUC 
                 280 
                 ACGGCGGAGACC 
                 516 
                 0.64 
                 36.30 
                 0.40 
                 60.12 
               
               
                 UCCGCCGU 
                   
                 TATGGCAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACAGCGGUCCAG 
                 281 
                 ACATCCTGCTGG 
                 517 
                 0.80 
                 19.94 
                 0.45 
                 55.14 
               
               
                 CAGGAUGU 
                   
                 ACCGCTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAAGCGCCUCCG 
                 282 
                 TGGCCTATCGGA 
                 518 
                 0.80 
                 19.89 
                 0.38 
                 62.04 
               
               
                 AUAGGCCA 
                   
                 GGCGCTTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCAAAGAAGAA 
                 283 
                 CACATCCCTTCTT 
                 519 
                 0.75 
                 24.87 
                 0.44 
                 56.19 
               
               
                 GGGAUGUG 
                   
                 CTTTGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CACGUAAUACUC 
                 284 
                 TGGTCATGGAGT 
                 520 
                 0.76 
                 24.40 
                 0.54 
                 46.50 
               
               
                 CAUGACCA 
                   
                 ATTACGTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUCUCGGCCGGA 
                 285 
                 GAGCGGATTCCG 
                 521 
                 0.88 
                 11.61 
                 0.34 
                 65.98 
               
               
                 AUCCGCUC 
                   
                 GCCGAGAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUUCAUCUUCA 
                 286 
                 AGCGGTAGTGAA 
                 522 
                 0.69 
                 31.44 
                 0.48 
                 51.78 
               
               
                 CUACCGCU 
                   
                 GATGAAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCAUCUCGGCC 
                 287 
                 CGGATTCCGGCC 
                 523 
                 0.81 
                 18.56 
                 0.14 
                 86.39 
               
               
                 GGAAUCCG 
                   
                 GAGATGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGGGACAGCCG 
                 288 
                 AGTTCCAGCGGC 
                 524 
                 0.68 
                 32.09 
                 0.41 
                 58.84 
               
               
                 CUGGAACU 
                   
                 TGTCCCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUGACAAUCUCC 
                 289 
                 TACCTGGCGGAG 
                 525 
                 0.58 
                 42.38 
                 0.40 
                 60.47 
               
               
                 GCCAGGUA 
                   
                 ATTGTCAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCCAUGACAAU 
                 290 
                 TGGCGGAGATTG 
                 526 
                 0.58 
                 42.38 
                 0.25 
                 75.00 
               
               
                 CUCCGCCA 
                   
                 TCATGGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUACUCCAUGAC 
                 291 
                 TGTACCTGGTCAT 
                 527 
                 0.77 
                 23.07 
                 0.43 
                 56.84 
               
               
                 CAGGUACA 
                   
                 GGAGTAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCUCUGCCUCG 
                 292 
                 CAACTACGCGAG 
                 528 
                 0.65 
                 35.38 
                 0.19 
                 81.18 
               
               
                 CGUAGUUG 
                   
                 GCAGAGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAAUGUCCGACA 
                 293 
                 GGAGACACTGTC 
                 529 
                 0.70 
                 30.09 
                 0.37 
                 63.41 
               
               
                 GUGUCUCC 
                   
                 GGACATTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGUUCCAUCUGC 
                 294 
                 AGCTGCGGGCAG 
                 530 
                 0.66 
                 33.74 
                 0.31 
                 68.72 
               
               
                 CCGCAGCU 
                   
                 ATGGAACG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCUUGUAGUGGA 
                 295 
                 CAAGATCGTCCA 
                 531 
                 0.83 
                 17.20 
                 0.34 
                 65.91 
               
               
                 CGAUCUUG 
                   
                 CTACAAGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUCUCCGCCAGG 
                 296 
                 CGCTTCTACCTGG 
                 532 
                 0.58 
                 42.37 
                 0.35 
                 65.50 
               
               
                 UAGAAGCG 
                   
                 CGGAGAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCAGGCUCUGC 
                 297 
                 CTCACCCGGCAG 
                 533 
                 0.70 
                 30.13 
                 0.37 
                 63.07 
               
               
                 CGGGUGAG 
                   
                 AGCCTGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCUUCAUCUUC 
                 298 
                 GCGGTAGTGAAG 
                 534 
                 0.71 
                 28.82 
                 0.40 
                 60.24 
               
               
                 ACUACCGC 
                   
                 ATGAAGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCAGGAUGUUGU 
                 299 
                 CAAACCCGACAA 
                 535 
                 0.56 
                 44.39 
                 0.22 
                 78.03 
               
               
                 CGGGUUUG 
                   
                 CATCCTGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCCUCAGCCUC 
                 300 
                 CTGCGGCAGAGG 
                 536 
                 0.80 
                 20.12 
                 0.29 
                 71.28 
               
               
                 UGCCGCAG 
                   
                 CTGAGGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGUUGUCGGGUU 
                 301 
                 GGACATCAAACC 
                 537 
                 0.79 
                 21.00 
                 0.58 
                 42.19 
               
               
                 UGAUGUCC 
                   
                 CGACAACA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCACGUAAUACU 
                 302 
                 GGTCATGGAGTA 
                 538 
                 0.79 
                 20.84 
                 0.50 
                 50.06 
               
               
                 CCAUGACC 
                   
                 TTACGTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCGUUCCAUCUG 
                 303 
                 GCTGCGGGCAGA 
                 539 
                 0.68 
                 31.74 
                 0.23 
                 77.46 
               
               
                 CCCGCAGC 
                   
                 TGGAACGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUCCCGAGUAAG 
                 304 
                 TCTGCCTGCTTAC 
                 540 
                 0.69 
                 31.49 
                 0.50 
                 49.81 
               
               
                 CAGGCAGA 
                   
                 TCGGGAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGAUCUUCAUGG 
                 305 
                 GGTGTATGCCAT 
                 541 
                 0.72 
                 27.70 
                 0.10 
                 89.68 
               
               
                 CAUACACC 
                   
                 GAAGATCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGGACAGCCGC 
                 306 
                 CAGTTCCAGCGG 
                 542 
                 0.71 
                 28.72 
                 0.55 
                 45.34 
               
               
                 UGGAACTG 
                   
                 CTGTCCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGUUUGAUGUC 
                 307 
                 TGCACAGGGACA 
                 543 
                 0.60 
                 40.12 
                 0.37 
                 62.61 
               
               
                 CCUGUGCA 
                   
                 TCAAACCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGACAAUCUCCG 
                 308 
                 CTACCTGGCGGA 
                 544 
                 0.61 
                 38.86 
                 0.33 
                 66.56 
               
               
                 CCAGGUAG 
                   
                 GATTGTCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CACAGCGGUCCA 
                 309 
                 CATCCTGCTGGAC 
                 545 
                 0.93 
                 6.62 
                 0.40 
                 59.58 
               
               
                 GCAGGAUG 
                   
                 CGCTGTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCGUAGAAGGGC 
                 310 
                 GGGCAGACGCCC 
                 546 
                 0.60 
                 39.53 
                 0.22 
                 77.91 
               
               
                 GUCUGCCC 
                   
                 TTCTACGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCAGCCUCUGC 
                 311 
                 TCCCTGCGGCAG 
                 547 
                 0.82 
                 17.86 
                 0.20 
                 79.58 
               
               
                 CGCAGGGA 
                   
                 AGGCTGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUCUCAGUGCAU 
                 312 
                 CGTTTTGGATGCA 
                 548 
                 0.81 
                 18.85 
                 0.54 
                 46.13 
               
               
                 CCAAAACG 
                   
                 CTGAGAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGACGAUCUUGC 
                 313 
                 GACCTATGGCAA 
                 549 
                 0.70 
                 29.82 
                 0.51 
                 48.97 
               
               
                 CAUAGGUC 
                   
                 GATCGTCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCAGCAGUGUCA 
                 314 
                 GGACCTGCTGAC 
                 550 
                 0.67 
                 33.46 
                 0.39 
                 61.11 
               
               
                 GCAGGUCC 
                   
                 ACTGCTGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUCCUGGGCGG 
                 315 
                 GTCTGGCGCCGC 
                 551 
                 0.91 
                 8.52 
                 0.21 
                 78.79 
               
               
                 CGCCAGAC 
                   
                 CCAGGAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCAGGAUGUUG 
                 316 
                 AAACCCGACAAC 
                 552 
                 0.59 
                 41.05 
                 0.26 
                 74.02 
               
               
                 UCGGGUUU 
                   
                 ATCCTGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUCCGCUCCUGC 
                 317 
                 CGGCAGTTGCAG 
                 553 
                 0.87 
                 12.80 
                 0.60 
                 40.06 
               
               
                 AACUGCCG 
                   
                 GAGCGGAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGAGCAGGGAA 
                 318 
                 GAGGCGCTTTCCC 
                 554 
                 0.67 
                 33.24 
                 0.38 
                 62.37 
               
               
                 AGCGCCUC 
                   
                 TGCTCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACACCUGGCCCG 
                 319 
                 GAAGCAGACGGG 
                 555 
                 0.67 
                 33.00 
                 0.45 
                 55.40 
               
               
                 UCUGCUUC 
                   
                 CCAGGTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCCAGCGCCCAC 
                 320 
                 TGTGACTGGTGG 
                 556 
                 0.62 
                 37.93 
                 0.32 
                 67.82 
               
               
                 CAGUCACA 
                   
                 GCGCTGGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUCCCUCUGCC 
                 321 
                 TTGCTGCAGGCA 
                 557 
                 0.74 
                 26.41 
                 0.30 
                 70.15 
               
               
                 UGCAGCAA 
                   
                 GAGGGAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUCAGGCUCUG 
                 322 
                 TCACCCGGCAGA 
                 558 
                 0.74 
                 25.69 
                 0.39 
                 60.71 
               
               
                 CCGGGUGA 
                   
                 GCCTGAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGAUGUCCCUG 
                 323 
                 TACGTGCACAGG 
                 559 
                 0.74 
                 25.67 
                 0.45 
                 55.13 
               
               
                 UGCACGUA 
                   
                 GACATCAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCUCAGCCUCU 
                 324 
                 CCTGCGGCAGAG 
                 560 
                 0.84 
                 16.37 
                 0.54 
                 46.42 
               
               
                 GCCGCAGG 
                   
                 GCTGAGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGUAGUUCUCAU 
                 325 
                 CTTCCAGGATGA 
                 561 
                 0.75 
                 25.48 
                 0.44 
                 56.15 
               
               
                 CCUGGAAG 
                   
                 GAACTACC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGCGCCCACCA 
                 326 
                 AGTGTGACTGGT 
                 562 
                 0.63 
                 37.28 
                 0.35 
                 64.93 
               
               
                 GUCACACU 
                   
                 GGGCGCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCCAAACUUGCU 
                 327 
                 CACTGCTGAGCA 
                 563 
                 0.63 
                 37.02 
                 0.38 
                 61.78 
               
               
                 CAGCAGUG 
                   
                 AGTTTGGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUUGCCAUAGGU 
                 328 
                 CGGCGGAGACCT 
                 564 
                 0.73 
                 27.04 
                 0.29 
                 71.05 
               
               
                 CUCCGCCG 
                   
                 ATGGCAAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UACACCUGGCCC 
                 329 
                 AAGCAGACGGGC 
                 565 
                 0.69 
                 31.10 
                 0.43 
                 57.43 
               
               
                 GUCUGCUU 
                   
                 CAGGTGTA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAGCGCCCACC 
                 330 
                 GTGTGACTGGTG 
                 566 
                 0.64 
                 36.17 
                 0.29 
                 70.96 
               
               
                 AGUCACAC 
                   
                 GGCGCTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCCUCAGCCUG 
                 331 
                 CTTTCGGCCAGGC 
                 567 
                 0.86 
                 14.49 
                 0.35 
                 64.80 
               
               
                 GCCGAAAG 
                   
                 TGAGGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAUCUCCGCCAG 
                 332 
                 GCTTCTACCTGGC 
                 568 
                 0.64 
                 35.85 
                 0.35 
                 65.27 
               
               
                 GUAGAAGC 
                   
                 GGAGATT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUGGCAUACACC 
                 333 
                 ACGGGCCAGGTG 
                 569 
                 0.86 
                 14.31 
                 0.50 
                 49.63 
               
               
                 UGGCCCGU 
                   
                 TATGCCAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAUGACAAUCU 
                 334 
                 CCTGGCGGAGAT 
                 570 
                 0.65 
                 34.53 
                 0.24 
                 76.46 
               
               
                 CCGCCAGG 
                   
                 TGTCATGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCCCCAAACUUG 
                 335 
                 CTGCTGAGCAAG 
                 571 
                 0.94 
                 5.73 
                 0.55 
                 44.67 
               
               
                 CUCAGCAG 
                   
                 TTTGGGGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAUGUUGUCGGG 
                 336 
                 ACATCAAACCCG 
                 572 
                 0.90 
                 10.06 
                 0.58 
                 42.42 
               
               
                 UUUGAUGU 
                   
                 ACAACATC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUUUGCCCAUCC 
                 337 
                 CCTGACGTGGAT 
                 573 
                 0.66 
                 34.36 
                 0.46 
                 54.49 
               
               
                 ACGUCAGG 
                   
                 GGGCAAAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGACGGCCCGG 
                 338 
                 GCAGCAAGCCGG 
                 574 
                 0.95 
                 5.42 
                 0.70 
                 30.41 
               
               
                 CUUGCUGC 
                   
                 GCCGTCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCCGCCAGGUA 
                 339 
                 CGCGCTTCTACCT 
                 575 
                 0.70 
                 30.22 
                 0.22 
                 78.14 
               
               
                 GAAGCGCG 
                   
                 GGCGGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUACAGGUAGUU 
                 340 
                 AGGATGAGAACT 
                 576 
                 0.68 
                 31.52 
                 0.34 
                 65.57 
               
               
                 CUCAUCCU 
                   
                 ACCTGTAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGGCGUCUGCC 
                 341 
                 GTTCTATGGGCA 
                 577 
                 0.87 
                 13.23 
                 0.41 
                 58.98 
               
               
                 CAUAGAAC 
                   
                 GACGCCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGGCCACAGCGG 
                 342 
                 CTGCTGGACCGCT 
                 578 
                 0.70 
                 29.59 
                 0.31 
                 69.44 
               
               
                 UCCAGCAG 
                   
                 GTGGCCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGUAGUUGACUG 
                 343 
                 AACTTCGCCAGTC 
                 579 
                 0.75 
                 25.26 
                 0.38 
                 61.52 
               
               
                 GCGAAGUU 
                   
                 AACTACG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUGCCGCAGGG 
                 344 
                 GCGGCTGTCCCTG 
                 580 
                 0.77 
                 22.97 
                 0.18 
                 82.10 
               
               
                 ACAGCCGC 
                   
                 CGGCAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAGCGCCUCCGA 
                 345 
                 CTGGCCTATCGG 
                 581 
                 0.91 
                 8.91 
                 0.56 
                 43.93 
               
               
                 UAGGCCAG 
                   
                 AGGCGCTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GACAGAACAACG 
                 346 
                 CTGTTCGCCGTTG 
                 582 
                 0.79 
                 21.41 
                 0.30 
                 70.49 
               
               
                 GCGAACAG 
                   
                 TTCTGTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUCAGCAGUGU 
                 347 
                 ACCTGCTGACACT 
                 583 
                 0.71 
                 29.18 
                 0.27 
                 73.46 
               
               
                 CAGCAGGU 
                   
                 GCTGAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUGAUCUUCAUG 
                 348 
                 GTGTATGCCATG 
                 584 
                 0.87 
                 12.76 
                 0.60 
                 39.97 
               
               
                 GCAUACAC 
                   
                 AAGATCAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUUGCCCAUCCA 
                 349 
                 CCCTGACGTGGA 
                 585 
                 0.67 
                 32.79 
                 0.41 
                 59.36 
               
               
                 CGUCAGGG 
                   
                 TGGGCAAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACUUGCUCAGCA 
                 350 
                 GCTGACACTGCT 
                 586 
                 0.72 
                 27.84 
                 0.39 
                 60.71 
               
               
                 GUGUCAGC 
                   
                 GAGCAAGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGAUGUCCCUGU 
                 351 
                 CTACGTGCACAG 
                 587 
                 0.79 
                 20.58 
                 0.41 
                 59.00 
               
               
                 GCACGUAG 
                   
                 GGACATCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAAUACCGAGGA 
                 352 
                 CCCGACATTCCTC 
                 588 
                 0.89 
                 11.25 
                 0.49 
                 50.91 
               
               
                 AUGUCGGG 
                   
                 GGTATTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCGAAUACACC 
                 353 
                 GGGCGCTGGGTG 
                 589 
                 0.80 
                 19.77 
                 0.31 
                 68.72 
               
               
                 CAGCGCCC 
                   
                 TATTCGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGACAAUAAAUA 
                 354 
                 TTCCTCGGTATTT 
                 590 
                 0.71 
                 29.37 
                 0.52 
                 48.20 
               
               
                 CCGAGGAA 
                   
                 ATTGTCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCCGUCUGCUUC 
                 355 
                 GTGAAGATGAAG 
                 591 
                 0.80 
                 20.31 
                 0.56 
                 43.97 
               
               
                 AUCUUCAC 
                   
                 CAGACGGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUGCCUGCAGCA 
                 356 
                 GATGGAGTTGCT 
                 592 
                 0.77 
                 23.10 
                 0.53 
                 46.69 
               
               
                 ACUCCAUC 
                   
                 GCAGGCAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCUCAGCCUCUG 
                 357 
                 CCCTGCGGCAGA 
                 593 
                 0.89 
                 10.87 
                 0.45 
                 55.22 
               
               
                 CCGCAGGG 
                   
                 GGCTGAGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUGUCCGGAAGU 
                 358 
                 AGCAGGCGACTT 
                 594 
                 0.77 
                 22.99 
                 0.26 
                 73.65 
               
               
                 CGCCUGCU 
                   
                 CCGGACAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCACGUGUGGC 
                 359 
                 CTGCTTGAGCCAC 
                 595 
                 0.89 
                 10.81 
                 0.36 
                 64.18 
               
               
                 UCAAGCAG 
                   
                 ACGTGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GACAAUAAAUAC 
                 360 
                 ATTCCTCGGTATT 
                 596 
                 0.71 
                 28.97 
                 0.52 
                 47.51 
               
               
                 CGAGGAAU 
                   
                 TATTGTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCAUGACAAUC 
                 361 
                 CTGGCGGAGATT 
                 597 
                 0.69 
                 30.96 
                 0.19 
                 81.00 
               
               
                 UCCGCCAG 
                   
                 GTCATGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUGUCCCGGAG 
                 362 
                 GGGATGGTCTCC 
                 598 
                 0.77 
                 22.57 
                 0.34 
                 66.27 
               
               
                 ACCAUCCC 
                   
                 GGGACAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUGACCAGGUA 
                 363 
                 ACTACCTGTACCT 
                 599 
                 0.81 
                 19.39 
                 0.41 
                 59.09 
               
               
                 CAGGUAGU 
                   
                 GGTCATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCGCCCACCAG 
                 364 
                 GAGTGTGACTGG 
                 600 
                 0.70 
                 30.36 
                 0.36 
                 63.67 
               
               
                 UCACACUC 
                   
                 TGGGCGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUCAGUGCAUC 
                 365 
                 ACGTTTTGGATGC 
                 601 
                 0.89 
                 10.88 
                 0.49 
                 51.34 
               
               
                 CAAAACGU 
                   
                 ACTGAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUUGGGCAGAUG 
                 366 
                 AGGCCCTCCATCT 
                 602 
                 0.65 
                 35.14 
                 0.30 
                 70.00 
               
               
                 GAGGGCCU 
                   
                 GCCCAAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAUGUCCCUGUG 
                 367 
                 GCTACGTGCACA 
                 603 
                 0.81 
                 18.99 
                 0.38 
                 62.46 
               
               
                 CACGUAGC 
                   
                 GGGACATC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGCAGUGUCAG 
                 368 
                 GGGACCTGCTGA 
                 604 
                 0.74 
                 25.67 
                 0.48 
                 51.97 
               
               
                 CAGGUCCC 
                   
                 CACTGCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUGACAAUCUC 
                 369 
                 ACCTGGCGGAGA 
                 605 
                 0.71 
                 29.45 
                 0.29 
                 70.52 
               
               
                 CGCCAGGU 
                   
                 TTGTCATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACUUGUUCAUGA 
                 370 
                 CATGAAGATCAT 
                 606 
                 0.75 
                 25.47 
                 0.47 
                 52.89 
               
               
                 UCUUCAUG 
                   
                 GAACAAGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUGGAAUCCGCG 
                 371 
                 CCCTTCTACGCGG 
                 607 
                 0.69 
                 30.55 
                 0.51 
                 49.34 
               
               
                 UAGAAGGG 
                   
                 ATTCCAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGGCCAUGACAA 
                 372 
                 GGCGGAGATTGT 
                 608 
                 0.70 
                 30.46 
                 0.27 
                 72.55 
               
               
                 UCUCCGCC 
                   
                 CATGGCCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGACAGACAAU 
                 373 
                 CGGTATTTATTGT 
                 609 
                 0.73 
                 27.19 
                 0.49 
                 50.50 
               
               
                 AAAUACCG 
                   
                 CTGTCCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCGCUCCCCAAA 
                 374 
                 TGAGCAAGTTTG 
                 610 
                 1.00 
                 0.28 
                 0.43 
                 56.82 
               
               
                 CUUGCUCA 
                   
                 GGGAGCGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGCUCAGGCUC 
                 375 
                 ACCCGGCAGAGC 
                 611 
                 0.82 
                 17.97 
                 0.31 
                 69.03 
               
               
                 UGCCGGGU 
                   
                 CTGAGCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCUCCUGGGCG 
                 376 
                 TCTGGCGCCGCCC 
                 612 
                 1.00 
                 0.05 
                 0.04 
                 96.23 
               
               
                 GCGCCAGA 
                   
                 AGGAGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUUCCCGAGUAA 
                 377 
                 CTGCCTGCTTACT 
                 613 
                 0.79 
                 20.69 
                 0.55 
                 44.89 
               
               
                 GCAGGCAG 
                   
                 CGGGAAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGAUGUUGUCGG 
                 378 
                 CATCAAACCCGA 
                 614 
                 0.96 
                 4.26 
                 0.59 
                 40.81 
               
               
                 GUUUGAUG 
                   
                 CAACATCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGGUAGUUCUC 
                 379 
                 TCCAGGATGAGA 
                 615 
                 0.74 
                 25.92 
                 0.23 
                 76.71 
               
               
                 AUCCUGGA 
                   
                 ACTACCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCCCAUAGAAC 
                 380 
                 TATGAAATGTTCT 
                 616 
                 0.92 
                 7.67 
                 0.65 
                 34.56 
               
               
                 AUUUCAUA 
                   
                 ATGGGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UAGUUCUCAUCC 
                 381 
                 GCCTTCCAGGAT 
                 617 
                 0.83 
                 16.83 
                 0.56 
                 43.88 
               
               
                 UGGAAGGC 
                   
                 GAGAACTA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUGUCCCUGUGC 
                 382 
                 GGCTACGTGCAC 
                 618 
                 0.83 
                 16.78 
                 0.51 
                 49.29 
               
               
                 ACGUAGCC 
                   
                 AGGGACAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGGCCCGGAUC 
                 383 
                 AGTCCTGTGATCC 
                 619 
                 0.83 
                 17.45 
                 0.33 
                 67.11 
               
               
                 ACAGGACU 
                   
                 GGGCCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGGACGAUCUUG 
                 384 
                 ACCTATGGCAAG 
                 620 
                 0.81 
                 19.20 
                 0.57 
                 42.52 
               
               
                 CCAUAGGU 
                   
                 ATCGTCCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUUGGCCGGCGU 
                 385 
                 GGTGGCCCACGC 
                 621 
                 1.02 
                 -1.82 
                 0.56 
                 43.57 
               
               
                 GGGCCACC 
                   
                 CGGCCAAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCAGUGCAUCC 
                 386 
                 CACGTTTTGGATG 
                 622 
                 0.92 
                 7.65 
                 0.46 
                 54.26 
               
               
                 AAAACGUG 
                   
                 CACTGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCGAAGUUGCAU 
                 387 
                 ACCGACACATGC 
                 623 
                 0.77 
                 22.96 
                 0.42 
                 58.15 
               
               
                 GUGUCGGU 
                   
                 AACTTCGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGGAACACGGAC 
                 388 
                 GCCGGGCCGTCC 
                 624 
                 1.02 
                 -1.90 
                 0.39 
                 60.96 
               
               
                 GGCCCGGC 
                   
                 GTGTTCCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCGAGAGCAGCG 
                 389 
                 CTCACTTGCGCTG 
                 625 
                 0.84 
                 16.13 
                 0.59 
                 40.93 
               
               
                 CAAGUGAG 
                   
                 CTCTCGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCCUGCAACUGC 
                 390 
                 CACGTCCGGCAG 
                 626 
                 0.84 
                 16.06 
                 0.55 
                 44.61 
               
               
                 CGGACGUG 
                   
                 TTGCAGGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCACCAACACGU 
                 391 
                 GGAGAGGGACGT 
                 627 
                 0.53 
                 47.12 
                 0.16 
                 84.09 
               
               
                 CCCUCUCC 
                   
                 GTTGGTGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCCUGCAGCAA 
                 392 
                 GGATGGAGTTGC 
                 628 
                 0.86 
                 13.99 
                 0.50 
                 49.75 
               
               
                 CUCCAUCC 
                   
                 TGCAGGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGGCCGGCGUG 
                 393 
                 TGGTGGCCCACG 
                 629 
                 1.03 
                 -3.19 
                 0.56 
                 44.37 
               
               
                 GGCCACCA 
                   
                 CCGGCCAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAGCCUCUGCCU 
                 394 
                 ACTACGCGAGGC 
                 630 
                 0.81 
                 18.77 
                 0.22 
                 77.78 
               
               
                 CGCGUAGU 
                   
                 AGAGGCTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAGGGCGUCUGC 
                 395 
                 TTCTATGGGCAG 
                 631 
                 0.87 
                 13.15 
                 0.65 
                 34.56 
               
               
                 CCAUAGAA 
                   
                 ACGCCCTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACAGACAAUAAA 
                 396 
                 CCTCGGTATTTAT 
                 632 
                 1.04 
                 -3.95 
                 0.26 
                 74.02 
               
               
                 UACCGAGG 
                   
                 TGTCTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGACAGACAAUA 
                 397 
                 TCGGTATTTATTG 
                 633 
                 0.77 
                 22.57 
                 0.47 
                 52.51 
               
               
                 AAUACCGA 
                   
                 TCTGTCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACGUGUGCCUCU 
                 398 
                 CGGGACCTAGAG 
                 634 
                 0.84 
                 16.47 
                 0.22 
                 77.73 
               
               
                 AGGUCCCG 
                   
                 GCACACGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCACGAGACAG 
                 399 
                 CCGTTGTTCTGTC 
                 635 
                 0.84 
                 16.10 
                 0.32 
                 68.01 
               
               
                 AACAACGG 
                   
                 TCGTGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGACCAGGUACA 
                 400 
                 GAACTACCTGTA 
                 636 
                 0.78 
                 22.00 
                 0.36 
                 63.73 
               
               
                 GGUAGUUC 
                   
                 CCTGGTCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCUGCCGGGUG 
                 401 
                 GAGGTGCTCACC 
                 637 
                 0.75 
                 25.25 
                 0.26 
                 74.36 
               
               
                 AGCACCUC 
                   
                 CGGCAGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GACAAUCUCCGC 
                 402 
                 TCTACCTGGCGG 
                 638 
                 0.76 
                 23.70 
                 0.50 
                 49.82 
               
               
                 CAGGUAGA 
                   
                 AGATTGTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUCCGCCAGGU 
                 403 
                 GCGCTTCTACCTG 
                 639 
                 0.80 
                 19.59 
                 0.33 
                 66.52 
               
               
                 AGAAGCGC 
                   
                 GCGGAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUCUGCCUCGCG 
                 404 
                 GTCAACTACGCG 
                 640 
                 0.83 
                 16.61 
                 0.09 
                 91.21 
               
               
                 UAGUUGAC 
                   
                 AGGCAGAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUUUGGGCAGAU 
                 405 
                 GGCCCTCCATCTG 
                 641 
                 0.72 
                 28.06 
                 0.33 
                 67.50 
               
               
                 GGAGGGCC 
                   
                 CCCAAAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACAGGUAGUUCU 
                 406 
                 CCAGGATGAGAA 
                 642 
                 0.79 
                 20.51 
                 0.15 
                 85.36 
               
               
                 CAUCCUGG 
                   
                 CTACCTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAAACUUGCTC 
                 407 
                 ACACTGCTGAGC 
                 643 
                 0.76 
                 23.64 
                 0.42 
                 57.70 
               
               
                 AGCAGUGU 
                   
                 AAGTTTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCGGGUUUGAUG 
                 408 
                 CACAGGGACATC 
                 644 
                 0.78 
                 22.49 
                 0.43 
                 57.16 
               
               
                 UCCCUGUG 
                   
                 AAACCCGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCUUGCUGCCU 
                 409 
                 GCCTGGGAAGGC 
                 645 
                 1.06 
                 -6.32 
                 0.52 
                 48.15 
               
               
                 UCCCAGGC 
                   
                 AGCAAGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UACAGGUAGUUC 
                 410 
                 CAGGATGAGAAC 
                 646 
                 0.80 
                 19.83 
                 0.27 
                 72.51 
               
               
                 UCAUCCUG 
                   
                 TACCTGTA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGCCCAUCCAC 
                 411 
                 GCCCTGACGTGG 
                 647 
                 0.78 
                 22.23 
                 0.33 
                 67.15 
               
               
                 GUCAGGGC 
                   
                 ATGGGCAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGUACAGGUAG 
                 412 
                 GATGAGAACTAC 
                 648 
                 0.81 
                 18.68 
                 0.41 
                 58.92 
               
               
                 UUCUCAUC 
                   
                 CTGTACCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GACAGACAAUAA 
                 413 
                 CTCGGTATTTATT 
                 649 
                 0.82 
                 18.26 
                 0.62 
                 38.07 
               
               
                 AUACCGAG 
                   
                 GTCTGTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UAGAACAUUUCA 
                 414 
                 TTCGCCTATGAAA 
                 650 
                 0.80 
                 20.23 
                 0.56 
                 43.67 
               
               
                 UAGGCGAA 
                   
                 TGTTCTA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGGCCUUUUAU 
                 415 
                 CCTCGCGAATAA 
                 651 
                 0.86 
                 13.63 
                 0.34 
                 66.43 
               
               
                 UCGCGAGG 
                   
                 AAGGCCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCUCGCGUAGU 
                 416 
                 GCCAGTCAACTA 
                 652 
                 0.87 
                 12.98 
                 0.09 
                 91.10 
               
               
                 UGACUGGC 
                   
                 CGCGAGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAGCAGGAUGU 
                 417 
                 ACCCGACAACAT 
                 653 
                 0.60 
                 40.29 
                 0.10 
                 89.59 
               
               
                 UGUCGGGU 
                   
                 CCTGCTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUAGUUGACUGG 
                 418 
                 GAACTTCGCCAG 
                 654 
                 0.93 
                 7.50 
                 0.55 
                 45.33 
               
               
                 CGAAGUUC 
                   
                 TCAACTAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCGGAUGGCCU 
                 419 
                 GGAGATGGAGGC 
                 655 
                 0.60 
                 40.15 
                 0.16 
                 84.43 
               
               
                 CCAUCUCC 
                   
                 CATCCGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACAAUCUCCGCC 
                 420 
                 TTCTACCTGGCGG 
                 656 
                 0.81 
                 19.09 
                 0.50 
                 49.75 
               
               
                 AGGUAGAA 
                   
                 AGATTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCGAAUACACCC 
                 421 
                 TGGGCGCTGGGT 
                 657 
                 0.93 
                 6.94 
                 0.30 
                 69.72 
               
               
                 AGCGCCCA 
                   
                 GTATTCGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUAGUUCUCAUC 
                 422 
                 CCTTCCAGGATG 
                 658 
                 0.93 
                 7.43 
                 0.45 
                 55.09 
               
               
                 CUGGAAGG 
                   
                 AGAACTAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGCUCAGGCUCU 
                 423 
                 CACCCGGCAGAG 
                 659 
                 0.93 
                 7.38 
                 0.34 
                 65.82 
               
               
                 GCCGGGUG 
                   
                 CCTGAGCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAUUCACCAAC 
                 424 
                 AGGGACGTGTTG 
                 660 
                 0.61 
                 39.26 
                 0.13 
                 86.83 
               
               
                 ACGUCCCU 
                   
                 GTGAATGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACCAGGUACAGG 
                 425 
                 GAGAACTACCTG 
                 661 
                 0.84 
                 16.09 
                 0.23 
                 76.96 
               
               
                 UAGUUCUC 
                   
                 TACCTGGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CTGCAGUUUGCC 
                 426 
                 CGTGGATGGGCA 
                 662 
                 1.11 
                 -10.69 
                 0.40 
                 60.08 
               
               
                 CAUCCACG 
                   
                 AACTGCAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGUUCAUGAUC 
                 427 
                 GCCATGAAGATC 
                 663 
                 0.86 
                 14.13 
                 0.55 
                 45.23 
               
               
                 UUCAUGGC 
                   
                 ATGAACAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGAUGUCCCUG 
                 428 
                 ACGTGCACAGGG 
                 664 
                 0.93 
                 6.92 
                 0.57 
                 43.07 
               
               
                 UGCACGU 
                   
                 ACATCAAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCGGUCCAGCAG 
                 429 
                 ACAACATCCTGCT 
                 665 
                 0.61 
                 38.84 
                 0.16 
                 83.64 
               
               
                 GAUGUUGU 
                   
                 GGACCGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUCUAUGGCCAU 
                 430 
                 AGATTGTCATGG 
                 666 
                 1.11 
                 -11.00 
                 0.27 
                 73.11 
               
               
                 GACAAUCU 
                   
                 CCATAGAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGAGCAGGGAAA 
                 431 
                 GGAGGCGCTTTC 
                 667 
                 0.79 
                 21.46 
                 0.12 
                 88.35 
               
               
                 GCGCCUCC 
                   
                 CCTGCTCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UGCCUCGCGUAG 
                 432 
                 CCAGTCAACTAC 
                 668 
                 0.89 
                 11.03 
                 0.12 
                 88.02 
               
               
                 UUGACUGG 
                   
                 GCGAGGCA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCGGAUGGCCUC 
                 433 
                 GGGAGATGGAGG 
                 669 
                 0.79 
                 21.25 
                 0.28 
                 71.77 
               
               
                 CAUCUCCC 
                   
                 CCATCCGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUUCAUAGGCGA 
                 434 
                 GGGTGTATTCGCC 
                 670 
                 0.94 
                 5.56 
                 0.47 
                 53.28 
               
               
                 AUACACCC 
                   
                 TATGAAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCUGUCAGCGA 
                 435 
                 CCTCCGACTCGCT 
                 671 
                 0.89 
                 10.81 
                 0.24 
                 75.67 
               
               
                 GUCGGAGG 
                   
                 GACAGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCACUUCAGCUG 
                 436 
                 GGATGAAACAGC 
                 672 
                 0.78 
                 22.40 
                 0.36 
                 64.20 
               
               
                 UUUCAUCC 
                   
                 TGAAGTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUCCGCUCCUG 
                 437 
                 GGCAGTTGCAGG 
                 673 
                 0.79 
                 21.04 
                 0.23 
                 76.81 
               
               
                 CAACUGCC 
                   
                 AGCGGATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUAGGGUUCAG 
                 438 
                 CGCGCTCCCTGA 
                 674 
                 0.78 
                 21.81 
                 0.17 
                 83.22 
               
               
                 GGAGCGCG 
                   
                 ACCCTAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CACCAACACGUC 
                 439 
                 AGGAGAGGGACG 
                 675 
                 0.62 
                 37.51 
                 0.18 
                 81.57 
               
               
                 CCUCUCCU 
                   
                 TGTTGGTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGGAGCAGGGA 
                 440 
                 AGGCGCTTTCCCT 
                 676 
                 0.88 
                 12.48 
                 0.48 
                 51.82 
               
               
                 AAGCGCCU 
                   
                 GCTCCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAAUCUCCGCCA 
                 441 
                 CTTCTACCTGGCG 
                 677 
                 0.84 
                 15.95 
                 0.51 
                 49.25 
               
               
                 GGUAGAAG 
                   
                 GAGATTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUGUUGUCGGGU 
                 442 
                 GACATCAAACCC 
                 678 
                 0.83 
                 16.93 
                 0.47 
                 52.83 
               
               
                 UUGAUGUC 
                   
                 GACAACAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAUCCGCUCCU 
                 443 
                 GCAGTTGCAGGA 
                 679 
                 0.80 
                 19.53 
                 0.28 
                 71.62 
               
               
                 GCAACUGC 
                   
                 GCGGATGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCGUCACCUCGG 
                 444 
                 GGCTGAGGCCGA 
                 680 
                 0.80 
                 20.02 
                 0.19 
                 81.27 
               
               
                 CCUCAGCC 
                   
                 GGTGACGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GAGGGCCUUUUA 
                 445 
                 CTCGCGAATAAA 
                 681 
                 0.92 
                 8.23 
                 0.38 
                 62.21 
               
               
                 UUCGCGAG 
                   
                 AGGCCCTC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCGGCAGAGAG 
                 446 
                 GAGCACCTCTCTC 
                 682 
                 0.80 
                 19.75 
                 0.09 
                 90.71 
               
               
                 AGGUGCUC 
                   
                 TGCCGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAUCCAAAACGU 
                 447 
                 CCCAATCCACGTT 
                 683 
                 0.81 
                 19.12 
                 0.22 
                 77.98 
               
               
                 GGAUUGGG 
                   
                 TTGGATG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGGGCAGAUGG 
                 448 
                 AAGGCCCTCCAT 
                 684 
                 0.81 
                 19.08 
                 0.22 
                 78.39 
               
               
                 AGGGCCUU 
                   
                 CTGCCCAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCUCUGCCUCGC 
                 449 
                 TCAACTACGCGA 
                 685 
                 0.93 
                 7.39 
                 0.15 
                 85.33 
               
               
                 GUAGUUGA 
                   
                 GGCAGAGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 ACAGAACAACGG 
                 450 
                 CCTGTTCGCCGTT 
                 686 
                 0.98 
                 2.07 
                 0.44 
                 55.96 
               
               
                 CGAACAGG 
                   
                 GTTCTGT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGGAUGUUGUC 
                 451 
                 TCAAACCCGACA 
                 687 
                 0.83 
                 17.17 
                 0.21 
                 79.31 
               
               
                 GGGUUUGA 
                   
                 ACATCCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGCCUCAGCCU 
                 452 
                 TGCGGCAGAGGC 
                 688 
                 0.93 
                 6.71 
                 0.40 
                 60.06 
               
               
                 CUGCCGCA 
                   
                 TGAGGCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGCAGGAUGUU 
                 453 
                 AACCCGACAACA 
                 689 
                 0.66 
                 34.18 
                 0.15 
                 84.54 
               
               
                 GUCGGGUU 
                   
                 TCCTGCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCAGAGAGAGGU 
                 454 
                 CAAGGAGCACCT 
                 690 
                 0.83 
                 17.29 
                 0.14 
                 85.95 
               
               
                 GCUCCUUG 
                   
                 CTCTCTGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCCAGUUCCAUG 
                 455 
                 CCCACACCCATG 
                 691 
                 0.84 
                 15.66 
                 0.22 
                 78.48 
               
               
                 GGUGUGGG 
                   
                 GAACTGGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCUCAGCCUGGC 
                 456 
                 TTCTTTCGGCCAG 
                 692 
                 0.83 
                 16.83 
                 0.36 
                 63.99 
               
               
                 CGAAAGAA 
                   
                 GCTGAGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGCCUUUUAUU 
                 457 
                 CCCTCGCGAATA 
                 693 
                 0.95 
                 5.11 
                 0.49 
                 50.65 
               
               
                 CGCGAGGG 
                   
                 AAAGGCCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUCGGCCAGGCG 
                 458 
                 GCCACATCCGCCT 
                 694 
                 0.85 
                 15.35 
                 0.25 
                 74.59 
               
               
                 GAUGUGGC 
                   
                 GGCCGAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCUUGCUGCCUU 
                 459 
                 GGCCTGGGAAGG 
                 695 
                 0.99 
                 1.14 
                 0.19 
                 81.01 
               
               
                 CCCAGGCC 
                   
                 CAGCAAGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGUCCAGCAGGA 
                 460 
                 CGACAACATCCT 
                 696 
                 0.68 
                 31.78 
                 0.20 
                 79.93 
               
               
                 UGUUGUCG 
                   
                 GCTGGACC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGGAGACCAUCC 
                 461 
                 CTCGACTGGGAT 
                 697 
                 0.86 
                 14.08 
                 0.20 
                 79.93 
               
               
                 CAGUCGAG 
                   
                 GGTCTCCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCUGCCUCGCGU 
                 462 
                 AGTCAACTACGC 
                 698 
                 0.96 
                 3.53 
                 0.13 
                 86.86 
               
               
                 AGUGACU 
                   
                 GAGGCAGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGUAGUUCUCA 
                 463 
                 TTCCAGGATGAG 
                 699 
                 0.93 
                 7.36 
                 0.37 
                 62.62 
               
               
                 UCCUGGAA 
                   
                 AACTACCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCCUUGUAGUGG 
                 464 
                 AAGATCGTCCAC 
                 700 
                 0.87 
                 12.96 
                 0.15 
                 84.87 
               
               
                 ACGAUCUU 
                   
                 TACAAGGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCAUCCAAAACG 
                 465 
                 CCAATCCACGTTT 
                 701 
                 0.97 
                 2.54 
                 0.27 
                 72.69 
               
               
                 UGGAUUGG 
                   
                 TGGATGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GUCCAGCAGGAU 
                 466 
                 CCGACAACATCC 
                 702 
                 0.70 
                 30.00 
                 0.17 
                 82.64 
               
               
                 GUGUCGG 
                   
                 TGCTGGAC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCUCCCGCAGC 
                 467 
                 GAGGTGACGCTG 
                 703 
                 0.86 
                 13.72 
                 0.20 
                 80.40 
               
               
                 GUCACCUC 
                   
                 CGGGAGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CGAGAGCAGCGC 
                 468 
                 CCTCACTTGCGCT 
                 704 
                 1.02 
                 -2.19 
                 0.63 
                 37.11 
               
               
                 AAGUGAGG 
                   
                 GCTCTCG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGGGAAAGCGC 
                 469 
                 TATCGGAGGCGC 
                 705 
                 0.89 
                 11.10 
                 0.08 
                 91.59 
               
               
                 CUCCGAUA 
                   
                 TTTCCCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AUUUCAUAGGCG 
                 470 
                 GGTGTATTCGCCT 
                 706 
                 1.05 
                 -4.54 
                 0.56 
                 44.15 
               
               
                 AAUACACC 
                   
                 ATGAAAT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UCGGCCAGGCGG 
                 471 
                 GGCCACATCCGC 
                 707 
                 0.73 
                 26.53 
                 0.17 
                 83.04 
               
               
                 AUGUGGCC 
                   
                 CTGGCCGA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AAGGGAUGUGUC 
                 472 
                 GACTTCCGGACA 
                 708 
                 0.90 
                 10.37 
                 0.26 
                 73.52 
               
               
                 CGGAAGUC 
                   
                 CATCCCTT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CUUGUAGUGGAC 
                 473 
                 GCAAGATCGTCC 
                 709 
                 0.76 
                 24.09 
                 0.11 
                 89.16 
               
               
                 GAUCUUGC 
                   
                 ACTACAAG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGUCGGCCAGGC 
                 474 
                 CCACATCCGCCTG 
                 710 
                 0.94 
                 6.15 
                 0.33 
                 67.44 
               
               
                 GGAUGUGG 
                   
                 GCCGACT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GCCUCAGCCUGG 
                 475 
                 TCTTTCGGCCAGG 
                 711 
                 1.05 
                 -4.82 
                 0.37 
                 63.11 
               
               
                 CCGAAAGA 
                   
                 CTGAGGC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGCGUCACCUCG 
                 476 
                 GCTGAGGCCGAG 
                 712 
                 0.78 
                 22.10 
                 0.35 
                 64.70 
               
               
                 GCCUCAGC 
                   
                 GTGACGCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CAGCGGCAGAGA 
                 477 
                 AGCACCTCTCTCT 
                 713 
                 0.96 
                 4.49 
                 0.14 
                 86.00 
               
               
                 GAGGUGCT 
                   
                 GCCGCTG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 CCAGCGGCAGAG 
                 478 
                 GCACCTCTCTCTG 
                 714 
                 0.97 
                 3.23 
                 0.15 
                 84.55 
               
               
                 AGAGGUGC 
                   
                 CCGCTGG 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 UUGUAGUGGACG 
                 479 
                 GGCAAGATCGTC 
                 715 
                 0.83 
                 17.22 
                 0.19 
                 81.05 
               
               
                 AUCUUGCC 
                   
                 CACTACAA 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 AGGGAAAGCGCC 
                 480 
                 CTATCGGAGGCG 
                 716 
                 1.01 
                 -1.12 
                 0.25 
                 75.50 
               
               
                 UCCGAUAG 
                   
                 CTTTCCCT 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 GGGAAAGCGCCU 
                 481 
                 CCTATCGGAGGC 
                 717 
                 0.90 
                 10.02 
                 0.23 
                 76.79 
               
               
                 CCGAUAGG 
                   
                 GCTTTCCC 
                   
                   
                   
                   
                   
               
               
                   
               
            
           
         
       
     
     Example 8: Selected Antisense Oligonucleotides Provided Dose-Dependent Reduction in DMPK Expression in Immortalized Myoblasts 
     Eighteen oligonucleotides from Example 7 were selected to be evaluated for their ability to reduce DMPK expression in a dose-responsive manner. DM1 C15 myoblasts were prepared as in Example 7 to yield differentiated myotubes in 96-well microplates. After seven days of differentiation, cells were transfected with individual oligonucleotides using Lipofectamine MessengerMax. Each oligonucleotide was tested in triplicate at concentrations of 0.046 nM, 0.137 nM, 0.412 nM, 1.235 nM, 3.704 nM, 11.11 nM, 33.33 nM, and 100 nM by 3-fold serial dilutions using 0.3 μL of Lipofectamine MessengerMax per well. 
     Following addition of oligonucleotide, cells were incubated for 72 hours prior to harvesting for total RNA. cDNA was synthesized from the total RNA extracts and qPCR was performed to determine expression levels of DMPK using a commercially available Taqman probeset in technical quadruplicate. All qPCR data were analyzed using a traditional ΔΔCT method and were normalized to a plate-based negative control that comprised of cells treated with vehicle control (0.3 μL/well Lipofectamine MessengerMax without any oligonucleotide). Data for each oligonucleotide to was fit to sigmoidal curve in order to determine an effective concentration of each oligonucleotide that provided a half-maximal response (EC-50). Results from these experiments are shown in Table 11. 
     Each of the eighteen antisense oligonucleotides selected for dose-dependent experimentation were capable of dose-dependently reducing DMPK in differentiated myotubes. Further, each of the tested antisense oligonucleotides reduced DMPK with EC-50 values below 25 nM. For example, antisense oligonucleotides comprising SEQ ID NOs: 362, 313, 320, 288, and 310 resulted in EC-50 values of 3.27 nM, 3.59 nM, 5.45 nM, 6.04 nM, and 24.59 nM, respectively. These data demonstrate that the antisense oligonucleotides shown in Table 11 are capable of dose-dependent reduction of DMPK in cellulo, suggesting that muscle-targeting complexes comprising these antisense oligonucleotides would be capable of targeting DMPK in muscle tissues in vivo. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Ability ofDMPK-targeting antisense oligonucleotides to reduce expression of 
               
               
                 DMPK in dose-dependent manner in cellulo 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Results 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 SEQ 
                   
                 SEQ 
                   
                 Percent DMPK 
               
               
                 Antisense Oligonucleotide 
                 NO: 
                 DMPK Target 
                 NO: 
                 EC-50 
                 reduction at 
               
               
                 Sequence 
                 ID 
                 Sequence 
                 ID 
                 (nM) 
                 100 nM 
               
               
                   
               
               
                 GCAGGAUGUUGUCGGGU 
                 299 
                 CAAACCCGACAA 
                 535 
                  0.1679 
                 89.77 
               
               
                 UUG 
                   
                 CATCCTGC 
                   
                   
                   
               
               
                   
               
               
                 AGCAGGAUGUUGUCGGG 
                 316 
                 AAACCCGACAAC 
                 552 
                  0.2266 
                 85.81 
               
               
                 UUU 
                   
                 ATCCTGCT 
                   
                   
                   
               
               
                   
               
               
                 GCGUAGAAGGGCGUCUG 
                 310 
                 GGGCAGACGCCC 
                 546 
                 24.59 
                 95.13 
               
               
                 CCC 
                   
                 TTCTACGC 
                   
                   
                   
               
               
                   
               
               
                 CCCAGCGCCCACCAGUC 
                 320 
                 TGTGACTGGTGG 
                 556 
                  5.454 
                 63.69 
               
               
                 ACA 
                   
                 GCGCTGGG 
                   
                   
                   
               
               
                   
               
               
                 CCAUCUCGGCCGGAAUC 
                 278 
                 GCGGATTCCGGC 
                 514 
                  0.44 
                 95.42 
               
               
                 CGC 
                   
                 CGAGATGG 
                   
                   
                   
               
               
                   
               
               
                 CGUUCCAUCUGCCCGCA 
                 294 
                 AGCTGCGGGCAG 
                 530 
                  0.19 
                 89.97 
               
               
                 GCU 
                   
                 ATGGAACG 
                   
                   
                   
               
               
                   
               
               
                 CAGGGACAGCCGCUGGA 
                 288 
                 AGTTCCAGCGGC 
                 524 
                  6.04 
                 90.59 
               
               
                 ACU 
                   
                 TGTCCCTG 
                   
                   
                   
               
               
                   
               
               
                 CAUGGCAUACACCUGGC 
                 257 
                 CGGGCCAGGTGT 
                 493 
                  0.42 
                 75.28 
               
               
                 CCG 
                   
                 ATGCCATG 
                   
                   
                   
               
               
                   
               
               
                 GCUUCAUCUUCACUACC 
                 286 
                 AGCGGTAGTGAA 
                 522 
                  0.03 
                 64.06 
               
               
                 GCU 
                   
                 GATGAAGC 
                   
                   
                   
               
               
                   
               
               
                 GAAUGUCCGACAGUGUC 
                 293 
                 GGAGACACTGTC 
                 529 
                  0.07 
                 97.23 
               
               
                 UCC 
                   
                 GGACATTC 
                   
                   
                   
               
               
                   
               
               
                 GGACGAUCUUGCCAUAG 
                 313 
                 GACCTATGGCAA 
                 549 
                  3.59 
                 92.18 
               
               
                 GUC 
                   
                 GATCGTCC 
                   
                   
                   
               
               
                   
               
               
                 GCUGUCCCGGAGACCAU 
                 362 
                 GGGATGGTCTCC 
                 598 
                  3.27 
                 93.07 
               
               
                 CCC 
                   
                 GGGACAGC 
                   
                   
                   
               
               
                   
               
               
                 GACAGAACAACGGCGAA 
                 346 
                 CTGTTCGCCGTTG 
                 582 
                  0.08 
                 94.32 
               
               
                 CAG 
                   
                 TTCTGTC 
                   
                   
                   
               
               
                   
               
               
                 UGUUGUCGGGUUUGAUG 
                 301 
                 GGACATCAAACC 
                 537 
                  0.21 
                 93.95 
               
               
                 UCC 
                   
                 CGACAACA 
                   
                   
                   
               
               
                   
               
               
                 CGAAUGUCCGACAGUGU 
                 260 
                 GAGACACTGTCG 
                 496 
                  0.18 
                 95.93 
               
               
                 CUC 
                   
                 GACATTCG 
                   
                   
                   
               
               
                   
               
               
                 GGGCCUGGGACCUCACU 
                 270 
                 GACAGTGAGGTC 
                 506 
                  0.07 
                 90.58 
               
               
                 GUC 
                   
                 CCAGGCCC 
                   
                   
                   
               
               
                   
               
               
                 CUCUGCCGCAGGGACAG 
                 272 
                 CGGCTGTCCCTG 
                 508 
                  0.42 
                 93.66 
               
               
                 CCG 
                   
                 CGGCAGAG 
                   
                   
                   
               
               
                   
               
               
                 UUGCCAUAGGUCUCCGC 
                 280 
                 ACGGCGGAGACC 
                 516 
                  0.37 
                 93.70 
               
               
                 CGU 
                   
                 TATGGCAA 
               
               
                   
               
            
           
         
       
     
     Example 9: Targeting DMPK in Mouse Muscle Tissues with a Muscle-Targeting Complex 
     The muscle-targeting complex described in Example 2, DTX-C-008, was tested for time-dependent inhibition of DMPK in mouse tissues in vivo. C57BL/6 wild-type mice were intravenously injected with a single dose of a vehicle control (phosphate-buffered saline (PBS)), control DMPK-ASO antisense oligonucleotide (ASO) (10 mg/kg of RNA), DTX-C-007 control complex (10 mg/kg of RNA), or DTX-C-008 (10 mg/kg of RNA) on Day 0 and euthanized after a prescribed period of time, as described in Table 12. One group of mice in each experimental condition was subjected to a second dose (multi-dose groups) at four weeks (Day 28). Following euthanization, the mice were segmented into isolated tissue types and samples of tibialis anterior and gastrocnemius muscle tissues were subsequently assayed for expression levels of DMPK ( FIGS.  13 A- 13 B ). 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Experimental conditions 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Weeks after 
                   
               
               
                   
                   
                 injection 
               
               
                   
                   
                 before 
                 Number of 
               
               
                 Group 
                 Dosage 
                 euthanization 
                 mice 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 1 
                 Single dose of vehicle (PBS) 
                 2 
                 5 
               
               
                 2 
                 Single dose of vehicle (PBS) 
                 4 
                 5 
               
               
                 3 
                 Single dose of vehicle (PBS) 
                 8 
                 3 
               
               
                 4 
                 Multi-dose of vehicle (PBS) 
                 8 
                 2 
               
               
                 5 
                 Single dose of vehicle (PBS) 
                 12 
                 5 
               
               
                 6 
                 Single dose of control DMPK-ASO 
                 2 
                 5 
               
               
                 7 
                 Single dose of control DMPK-ASO 
                 4 
                 5 
               
               
                 8 
                 Single dose of control DMPK-ASO 
                 8 
                 5 
               
               
                 9 
                 Multi-dose of control DMPK-ASO 
                 8 
                 5 
               
               
                 10 
                 Single dose of control DMPK-ASO 
                 12 
                 5 
               
               
                 11 
                 Single dose of DTX-C-007 control 
                 2 
                 5 
               
               
                 12 
                 Single dose of DTX-C-007 control 
                 4 
                 5 
               
               
                 13 
                 Single dose of DTX-C-007 control 
                 8 
                 5 
               
               
                 14 
                 Multi-dose of DTX-C-007 control 
                 8 
                 5 
               
               
                 15 
                 Single dose of DTX-C-007 control 
                 12 
                 5 
               
               
                 16 
                 Single dose of DTX-C-008 
                 2 
                 5 
               
               
                 17 
                 Single dose of DTX-C-008 
                 4 
                 5 
               
               
                 18 
                 Single dose of DTX-C-008 
                 8 
                 5 
               
               
                 19 
                 Multi-dose of DTX-C-008 
                 8 
                 5 
               
               
                 20 
                 Single dose of DTX-C-008 
                 12 
                 5 
               
               
                   
               
            
           
         
       
     
     Mice treated with the DTX-C-008 complex demonstrated about 50-60% reduction in DMPK expression in tibialis anterior muscle ( FIG.  13 A ) and about 30-50% reduction in DMPK expression in gastrocnemius muscle ( FIG.  13 B ) for all of Groups 16-20 (2-12 weeks between injection and euthanization), relative to vehicle. These data show that a single dose of the muscle-targeting complex DTX-C-008 inhibits expression of DMPK for at least twelve weeks following administration of the complex. 
     In contrast, mice treated with the naked antisense oligonucleotide or the control complex did not demonstrate significant inhibition of DMPK expression across all experimental groups and tissues. 
     These data demonstrate that a muscle-targeting complex as described herein is capable of providing persistent inhibition of DMPK expression in vivo for up to 12 weeks following a single dose or administration of said muscle targeting complex. 
     Example 10: A Muscle-Targeting Complex can Target Gene Expression in the Nucleus 
     A muscle-targeting complex as described in Example 2, DTX-C-008, was tested for inhibition of nuclear-retained DMPK RNA in mouse muscle tissues. The mice used for this Example have been engineered to express a human mutant DMPK gene—DMPK CUG380 hets having a G-for-C single-nucleotide polymorphism. As shown in  FIG.  14 A , the human mutant DMPK RNA is retained in the nucleus, while the mouse wild-type DMPK RNA is located in the cytoplasm and the nucleus. 
     Mice were intravenously injected with a single dose of a vehicle control (saline), a control complex DTX-C-007 (10 mg/kg of ASO), control DMPK-ASO (10 mg/kg of RNA), DTX-C-008 (10 mg/kg of ASO) and euthanized after 14 days. Six mice were treated in each experimental condition. Following euthanization, the mice were segmented into isolated tissue types and tissue samples were subsequently assayed for expression levels of mutant and wild-type DMPK ( FIG.  14 B ). 
     Mice treated with the muscle-targeting complex DTX-C-008 demonstrated statistically significant reduction in both nuclear-retained mutant DMPK and wild-type DMPK. (p-value &lt;0.05). These data demonstrate that a muscle-targeting complex as described herein is capable of targeting DMPK in the nucleus. 
     Example 11: A Muscle-Targeting Complex Reverses Myotonia in HSA LR  Mouse Model 
     A muscle-targeting complex (DTX-Actin) was generated comprising an antisense oligonucleotide that targets actin (Actin-gapmer-1) covalently linked to DTX-A-002 (RI7 217 (Fab)), an anti-transferrin receptor antibody. 
     Actin-gapmer-1 is a 2′-MOE 5-10-5 gapmer that comprises: 5′-NH 2 —(CH 2 ) 6 -dA*oC*oC*oA*oT*oT*dT*dTMCMT*dTMCMCMAMCMA*oG*oG*oG*oC*oT-3 (SEQ ID NO: 761); wherein ‘*’ represents a PS linkage; ‘d’ represents a deoxynucleic acid; and ‘o’ represents a 2′-MOE. 
     DTX-Actin was then tested for its ability to reduce target gene expression (hACTA1) and reduce myotonia in HSA LR  mice, a mouse model that has a functional myotonia phenotype similar to that observed in human DM1 patients. Details of the HSA LR  mouse model are as described in Mankodi, A. et al. Science. 289: 1769, 2000. HSA LR  mice were intravenously injected with a single dose of PBS or DTX-Actin (either 10 mg/kg or 20 mg/kg ASO). Each of these three experimental conditions were replicated in two individual mice. On Day 14 after injection, mice were euthanized and specific muscles were collected—quadriceps (quad), gastrocnemius (gastroc) and tibialis anterior (TA). The muscle tissues were analyzed for expression of hACTA1. DTX-Actin demonstrated reduction of hACTA1 expression in all three muscle tissues relative to vehicle control ( FIG.  15 A ). 
     On Day 14 after injection, and prior to the euthanasia and tissue collection described above, electromyography (EMG) was performed on specific muscles. EMG myotonic discharges were graded by a blinded examiner on a 4-point scale: 0, no myotonia; 1, occasional myotonic discharge in less than 50% of needle insertions; 2, myotonic discharge in greater than 50% of needle insertions; and 3: myotonic discharge with nearly every insertion. DTX-Actin demonstrated reduction in graded myotonia in all three muscle tissues relative to vehicle control ( FIG.  15 B ). Mice treated with 20 mg/kg DTX-Actin demonstrated little-to-no myotonia in quadriceps and gastrocnemius muscles. 
     These data demonstrate that a single dose of a muscle-targeting complex is capable of gene-specific targeting and reduction in functional myotonia in in the HSA LR  mice, a mouse model that has a functional myotonia phenotype similar to that observed in human DM1 patients. 
     Example 12: A Muscle-Targeting Complex can Functionally Correct Arrhythmia in a DM1 Mouse Model 
     A muscle-targeting complex as described in Example 2, DTX-C-008, was tested for its ability to functionally correct arrhythmia in a DM1 mouse model. The mice used for this Example are the offspring of mice expressing myosin heavy chain reverse tet transactivator (MHCrtTA) and mice expressing a mutant form of human DMPK (CUG 960 ).  FIG.  16 A  shows the structure of the mutant DMPK construct. 
     Doxycycline containing chow (2 g doxycycline/kg chow, Bio-Serv) was provided to the mice beginning at postnatal day 1, initially through the nursing dam and subsequently through chow after weaning, to induce selective expression of mutant DMPK in the heart. All mice were maintained on chow containing doxycycline throughout the entire course of the study except the “off Dox Control” group. At 12 weeks of age, all mice underwent a baseline pre-dose ECG evaluation. Mice were then treated intravenously with a single dose of either vehicle (saline), control DMPK-ASO (10 mg/kg), DTX-C-008 (10 mg/kg) or DTX-C-008 (20 mg/kg). Following baseline pre-dose ECG evaluation mice in the “off Dox Control” group were switched to chow without doxycycline. Post dose ECG evaluations were performed in all mice 7 and 14 days after treatment, or in the case of the “off Dox Control” group 7 and 14 days after reversion to chow without doxycycline. For each ECG spectra, QRS ( FIG.  16 B ) and QTc ( FIG.  16 C ) intervals were measured. 
     In this model, mice treated with doxycycline exhibit prolongation of QRS and QTC intervals driven by expression of mutant DMPK in the heart, similar to those reported in DM1 patients, and consistent with increased propensity for cardiac arrhythmia. Removal of doxycycline for the diet in the “Off Dox Control” group turns off expression of mutant DMPK, resulting in a normalization of QRS and QTC intervals. Mice maintained on doxycycline and treated with 20 mg/kg of the muscle-targeting complex DTX-C-008 demonstrated statistically significant reduction in their QTc intervals after 14 days despite continued expression of mutant DMPK in the heart ( FIG.  16 C ). This reduction in QTc intervals represents a correction in cardiac arrhythmia in a DM1 mouse model. These data demonstrate that a muscle-targeting complex as described herein is capable of providing a phenotypic and therapeutic benefit in a DM1 model. 
     Example 13: A Muscle-Targeting Complex can Target DMPK and Correct DM1-Related Genetic Splicing 
     In isolated muscles cells derived from human DM1 patients, a muscle-targeting complex as described in Example 5, DTX-C-012, which comprises a 15G11 antibody, was tested for reduction of DMPK expression and subsequent correction of splicing defects in Bin1, a downstream gene of DMPK. 
     Briefly, patient cells were seeded at a density of 10 k cells/well before being allowed to recover overnight. Cells were then treated with PBS (vehicle control), control DMPK-ASO, or DTX-C-012 (500 nM; equivalent to 55.5 nM ASO). Cells were allowed to differentiate for 14 days. Expression levels of DMPK and % Bin1 exon-11 inclusion were determined on Days 10, 11, 12, 13, and 14 post differentiation. 
     Treatment of DM1 patient cells with the DTX-C-012 complex leads to reduction of DMPK levels as early as Day 10 post differentiation ( FIG.  17 A ). Treatment of DM1 patient cells with the DTX-C-012 complex also leads to a statistically significant time-dependent change in Bin1 splicing ( FIG.  17 B ). (**p&lt;0.01, ***p&lt;0.001). These data demonstrate that a muscle-targeting complex comprising a 15G11 antibody as described herein is capable of providing phenotypic and therapeutic benefit (increased correction of DM1 gene-specific splicing) in a DM1 model. 
     Example 14: Selected Antisense Oligonucleotides Provided Dose-Dependent Reduction in DMPK Expression in DM1 and NHP Myotubes 
     The antisense oligonucleotides listed in Table 11 were further assessed to identify oligos that are safe in vivo (e.g., as indicated by low immunogenicity as measured by cytokine induction), and further based on manufacturability and secondary structure considerations. Three antisense oligonucleotides from Table 11, GCGUAGAAGGGCGUCUGCCC (SEQ ID NO: 310, DMPK-ASO-1), CCCAGCGCCCACCAGUCACA (SEQ ID NO: 320, DMPK-ASO-2), and CCAUCUCGGCCGGAAUCCGC (SEQ ID NO: 278, DMPK-ASO-3) were selected. These oligonucleotides were then further evaluated for their ability to reduce DMPK expression in DM1 myotubes and NHP myotubes in a dose-responsive manner. The tool compound (control DMPK-ASO) was used as control. Each of the antisense oligonucleotides were capable of dose-dependently reducing DMPK in DM1 and NHP myotubes (see  FIGS.  18 A- 18 C  and  FIGS.  19 A- 19 B , respectively). 
     These data demonstrate that these antisense oligonucleotides are safe in vivo and are capable of dose-dependent reduction of DMPK in cellulo, suggesting that muscle-targeting complexes comprising these antisense oligonucleotides would be capable of targeting DMPK in muscle tissues in vivo. 
     Example 15: Binding Affinity of Selected Anti-TfR1 Antibodies in Table 2 to Human TfR1 
     Selected anti-TfR1 antibodies were tested for their binding affinity to human TfR1 for measurement of Ka (association rate constant), Kd (dissociation rate constant), and K D  (affinity). Two known anti-TfR1 antibodies were used as control, 15G11 and OKT9. The binding experiment was performed on Carterra LSA at 25 C. An anti-mouse IgG and anti-human IgG antibody “lawn” was prepared on a HC30M chip by amine coupling. 59 IgGs (58 mouse mAbs and 1 human mAb) were captured on the chip. Dilution series of hTfR1, cyTfR1, and hTfR2 were injected to the chip for binding (starting from 1000 nM, 1:3 dilution, 8 concentrations). 
     Binding data were referenced by subtracting the responses from a buffer analyte injection and globally fitting to a 1:1 Langmuir binding model for estimate of Ka (association rate constant), Kd (dissociation rate constant), and K D  (affinity) using the Carterra™ Kinetics software. 5-6 concentrations were used for curve fitting. 
     The result showed the mouse mAbs demonstrated binding to hTfR1 with K D  values ranging from 13 pM to 50 nM. A majority of the mouse mAbs had K D  values in the single digit nanomolar to sub-nanomolar range. The tested mouse mAbs showed cross-reactive binding to cyTfR1 with K D  values ranging from 16 pM to 22 nM. 
     Ka, Kd, and K D  values of anti-TfR1 antibodies are provided in Table 13. 
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 Ka, Kd, and K D  values of anti-TfR1 antibodies 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Name 
                 K D  (M) 
                 Ka (M) 
                 Kd (M) 
               
               
                   
                   
               
               
                   
                 ctrl-15G11 
                 2.83E−10 
                 3.70E+05 
                 1.04E−04 
               
               
                   
                 ctrl-OKT9 mIgG 
                 5.36E−10 
                 7.74E+05 
                 4.15E−04 
               
               
                   
                 3-A04 
                 4.36E−10 
                 4.47E+05 
                 1.95E−04 
               
               
                   
                 3-M12 
                 7.68E−10 
                 1.66E+05 
                 1.27E−04 
               
               
                   
                 5-H12 
                 2.08E−07 
                 6.67E+04 
                 1.39E−02 
               
               
                   
                 10-H02 
                 2.72E−09 
                 1.26E+05 
                 3.42E−04 
               
               
                   
                 10-P05 
                 1.63E−09 
                 1.70E+05 
                 2.78E−04 
               
               
                   
                 2-H19 
                 2.06E−09 
                 2.22E+05 
                 4.56E−04 
               
               
                   
                 3-E05 
                 4.55E−10 
                 2.20E+04 
                 1.00E−05 
               
               
                   
                 3-F03 
                 2.23E−09 
                 1.38E+05 
                 3.09E−04 
               
               
                   
                 3-M09 
                 2.54E−09 
                 1.50E+05 
                 3.82E−04 
               
               
                   
                 3-P24 
                 9.70E−10 
                 6.72E+04 
                 6.52E−05 
               
               
                   
                 4-C05 
                 1.61E−09 
                 3.01E+04 
                 4.85E−05 
               
               
                   
                 4-H04 
                 1.39E−08 
                 6.17E+04 
                 8.57E−04 
               
               
                   
                 4-O12 
                 1.80E−09 
                 7.98E+04 
                 1.43E−04 
               
               
                   
                 6-D03 
                 9.86E−10 
                 1.08E+05 
                 1.07E−04 
               
               
                   
                 8-D15 
                 8.22E−09 
                 3.13E+04 
                 2.57E−04 
               
               
                   
                 8-K06 
                 6.94E−11 
                 1.44E+05 
                 1.00E−05 
               
               
                   
                 8-O17 
                 1.83E−09 
                 4.99E+04 
                 9.12E−05 
               
               
                   
                 9-C04 
                 1.41E−08 
                 4.10E+04 
                 5.75E−04 
               
               
                   
                 9-D04 
                 5.86E−09 
                 4.20E+04 
                 2.46E−04 
               
               
                   
                 9-K23 
                 4.01E−10 
                 5.40E+04 
                 2.17E−05 
               
               
                   
                   
               
            
           
         
       
     
     Example 16: Conjugation of Anti-TfR1 Antibodies with Oligonucleotides 
     Complexes containing an anti-TfR1 antibody listed in Table 2 covalently conjugated to a tool oligo (control DMPK-ASO) were generated. First, Fab′ fragments of anti-TfR antibody clones 3-A4, 3-M12, 5-H12, 8-K6, 9-K23, 3-E5, 6-D3, 4-O12, 4-O5, 10-P5, 2-H19, 3-F3, 8-O17, 3-M9, 10-H2, 4-J22, 9-D4, 8-D15, 4-H4, and 9-C4 were prepared by cutting the mouse monoclonal antibodies with an enzyme in or below the hinge region of the full IgG followed by partial reduction. The Fab&#39;s were confirmed to be comparable to mAbs in avidity or affinity. 
     Muscle-targeting complexes was generated by covalently linking the anti-TfR mAbs to the control DMPK-ASO via a cathepsin cleavable linker. Briefly, a Bicyclo[6.1.0]nonyne-PEG3-L-valine-L-citrulline-pentafluorophenyl ester (BCN-PEG3-Val-Cit-PFP) linker molecule was coupled to control DMPK-ASO through a carbamate bond. Excess linker and organic solvents were removed by tangential flow filtration (TFF). The purified Val-Cit-linker-ASO was then coupled to an azide functionalized anti-transferrin receptor antibody generated through modifying ε-amine on lysine with Azide-PEG4-PFP. A positive control muscle-targeting complex was also generated using 15G11. 
     The product of the antibody coupling reaction was then subjected to two purification methods to remove free antibody and free payload: 1) hydrophobic interaction chromatography (HIC-HPLC), and 2) Size exclusion chromatography (SEC). The HIC column utilized a decreasing salt gradient to separate free antibody from conjugate. During SEC, fractionation was performed based on A260/A280 traces to specifically collect conjugated material. Concentrations of the conjugates were determined by either Nanodrop A280 or BCA protein assay (for antibody) and Quant-It Ribogreen assay (for payload). Corresponding drug-antibody ratios (DARs) were calculated. DARs ranged between 0.8 and 2.0, and were standardized so that all samples receive equal amounts of payload. 
     The purified complexes were then tested for cellular internalization and inhibition of the target gene, DMPK. Non-human primate (NHP) or DM1 (donated by DM1 patients) cells were grown in 96-well plates and differentiated into myotubes for 7 days. Cells were then treated with escalating concentrations (0.5 nM, 5 nM, 50 nM) of each complex for 72 hours. Cells were harvested, RNA was isolated, and reverse transcription was performed to generate cDNA. qPCR was performed using TaqMan kits specific for Ppib (control) and DMPK on the QuantStudio 7. The relative amounts of remaining DMPK transcript in treated vs non-treated cells was were calculated and the results are shown in Table 14 and  FIG.  20   . 
     The results demonstrated that the anti-TfR1 antibodies are able to target muscle cells, be internalized by the muscle cells with the molecular payload (the tool oligo control DMPK-ASO), and that the molecular payload (DMPK ASO) are able to target and knockdown the target gene (DMPK). 
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 Binding Affinity of anti-TfR1 Antibodies and Efficacy of Conjugates 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % knockdown 
               
               
                   
                   
                   
                 % knockdown of 
                 of DMPK in cells 
               
               
                   
                   
                   
                 DMPK in NHP 
                 from human DM1 
               
               
                   
                 huTfR1 Avg 
                 cyTfR1 Avg 
                 cells using 
                 patients using 
               
               
                   
                 K D  (M) 
                 K D  (M) 
                 Antibody-DMPK 
                 Antibody-DMPK 
               
               
                 Clone Name 
                 (antibody alone) 
                 (antibody alone) 
                 ASO conjugate 
                 ASO conjugate 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 15G11 (control) 
                   8.0E−10 
                  1.0E−09 
                 36 
                 46 
               
               
                 3-A4 
                   4.36E−10 
                 2.32E−09 
                 77 
                 70 
               
               
                 3-M12 
                   7.68E−10 
                 5.18E−09 
                 77 
                 52 
               
               
                 5-H12 
                 2.02316E−07 
                 1.20E−08 
                 88 
                 57 
               
               
                 8-K6 
                 6.78121E−11 
                 3.76E−10 
                 73 
                 34 
               
               
                 9-K23 
                 3.19783E−10 
                 6.62E−10 
                 47 
                 −4 
               
               
                 3-E5 
                   4.55E−10 
                 6.71E−10 
                 59 
                 71 
               
               
                 6-D3 
                   9.86E−10 
                 7.78E−10 
                 −8 
                 −5 
               
               
                 4-O12 
                 1.27416E−09 
                 2.70E−07 
                 −16 
                 10 
               
               
                 4-C5 
                 1.38324E−09 
                 1.36E−08 
                 −20 
                 35 
               
               
                 10-P5 
                   1.63E−09 
                 1.10E−08 
                 58 
                 55 
               
               
                 2-H19 
                   2.06E−09 
                 5.75E−09 
                 39 
                 24 
               
               
                 3-F3 
                   2.23E−09 
                 1.84E−08 
                 −15 
                 20 
               
               
                 8-O17 
                 2.24245E−09 
                 1.10E−09 
                 26 
                 41 
               
               
                 3-M9 
                 2.50135E−09 
                 4.37E−09 
                 52 
                 39 
               
               
                 10-H2 
                   2.72E−09 
                 1.24E−08 
                 2 
                 16 
               
               
                 4-J22 
                   3.41E−09 
                 1.37E−09 
                 7 
                 57 
               
               
                 9-D4 
                 5.79556E−09 
                 8.68E−10 
                 42 
                 62 
               
               
                 8-D15 
                 9.15057E−09 
                 1.11E−08 
                 * 
                 * 
               
               
                 4-H4 
                   1.39E−08 
                 2.18E−08 
                 * 
                 * 
               
               
                 9-C4 
                 1.47657E−08 
                 1.20E−08 
                 * 
                 * 
               
               
                   
               
               
                 * very low yield from expression/conjugation 
               
            
           
         
       
     
     Interestingly, the DMPK knockdown results showed a lack of correlation between the binding affinity of the anti-TfR to transferrin receptor and efficacy in delivering a DMPK ASO to cells for DMPK knockdown. Surprisingly, the anti-TfR antibodies provided herein (e.g., at least 3-A4, 3-M12, 5-H12, 8-K6, 3-E5, 10-P5, 3-M9, and 9-D4) demonstrated superior activity in delivering a payload (e.g., DMPK ASO) to the target cells and achieving the biological effect of the molecular payload (e.g., DMPK knockdown) in either cyno cells or human DM1 patient cells, compared to the control antibody 15G11, despite the comparable binding affinity (or, in certain instances, such as 5-H12, lower binding affinity) to human or cyno transferrin receptor between these antibodies and the control antibody 15G11. 
     Top attributes such as high huTfR1 affinity, &gt;50% knockdown of DMPK in NHP and DM1 patient cell line, identified epitope binding with 3 unique sequences, low/no predicted PTM sites, and good expression and conjugation efficiency were considered for the selection of clones for humanization. 
     Example 16. Binding Activities of the Anti-TfR1 Antibodies 
     The screen identified 1 scFv clone (shown in Table 7), which was reformatted into different formats. The binding activity of selected formats were tested against human TfR1, cyno TfR1, and human TfR2 in an ELISA assay. 15G11 was used as control in this experiment. The results show that all tested antibodies bind to human TfR1 and cyno TfR1 ( FIGS.  21 A and  21 B ), but do not bind to human TfR2 ( FIG.  22   ). The EC50 values for each tested antibody are provided in Table 15. 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 EC50 (nM) values for anti-TfR antibodies 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                   
                 hIgG1 (with 
                   
                   
               
               
                   
                   
                   
                 L234A/L235A 
               
               
                   
                   
                   
                 mutations in HC 
               
               
                   
                 15G11 
                 ScFv 
                 constant region) 
                 FAB 
                 scFv_C_Fc 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Cyno TfR1 
                 1.08 
                 14.75 
                 22.01 
                 63.89 
                 27.21 
               
               
                 Human TfR1 
                 0.589 
                 24.8 
                 75.83 
                 101.9 
                 49.56 
               
               
                   
               
            
           
         
       
     
     Example 17: Conjugation of Anti-TfR1 Antibodies with Oligonucleotides 
     Complexes containing an anti-TfR1 Fab (Table 7) covalently conjugated to a tool oligo, control DMPK-ASO (targeting DMPK), were generated. The TfR Fab tested comprises a VH of SEQ ID NO: 204 and a VL of SEQ ID NO: 205. A Fab′ fragment of a known anti-TfR antibody, 15G11 was generated and used to produce a complex as positive control. 
     Muscle-targeting complexes was generated by covalently linking the anti-TfR antibodies to control DMPK-ASO via a cathepsin cleavable linker. The purified Val-Cit-linker-ASO was coupled to functionalized anti-transferrin receptor antibodies generated through modifying ε-amine on lysine of the antibody. 
     The product of the antibody coupling reaction was then subjected to two purification methods to remove free antibody and free payload: 1) hydrophobic interaction chromatography (HIC-HPLC), and 2) Size exclusion chromatography (SEC). The HIC column utilized a decreasing salt gradient to separate free antibody from conjugate. During SEC, fractionation was performed based on A260/A280 traces to specifically collect conjugated material. Concentrations of the conjugates were determined by either Nanodrop A280 or BCA protein assay (for antibody) and Quant-It Ribogreen assay (for payload). Corresponding drug-antibody ratios (DARs) were calculated. DAR was about 2.05. 
     The purified complexes were then tested for cellular internalization and inhibition of DMPK. Non-human primate (NHP) or DM1 (donated by DM1 patients) cells were grown in 96-well plates and differentiated into myotubes for 7 days. Cells were then treated with escalating concentrations (0.5 nM, 5 nM, 50 nM) of each complex for 72 hours. Cells were harvested, RNA was isolated, and reverse transcription was performed to generate cDNA. qPCR was performed using TaqMan kits specific for Ppib (control) and DMPK on the QuantStudio 7. The relative amounts of remaining DMPK transcript in treated vs non-treated cells was were calculated and the results are shown in  FIG.  23   . The complex containing anti-TfR Fab described herein achieved comparable DMPK knockdown as the complex containing 15G11. 
     The results demonstrated that the anti-TfR1 antibodies are able to target muscle cells, be internalized by the muscle cells with the molecular payload (the tool oligo control DMPK-ASO), and that the molecular payload (DMPK ASO) are able to target and knockdown the target gene (DMPK). 
     Example 18. Binding and Biological Activity of Anti-TfR-Oligonucleotide Conjugates 
     The anti-TfR antibody described herein (e.g., as in Table 7) alone or in a conjugate where the antibody was conjugated to a DMPK-targeting oligonucleotide (control DMPK-ASO) were tested for binding to human ( FIG.  24 A ) and cynomolgus monkey (FIG.  24 B) TfR1. Results demonstrate that binding of the anti-TfR antibody to both hTfR1 and cynoTfR1 increases 3-6-fold upon conjugation to DMPK-targeting oligonucleotide. 
     The conjugate was also tested in cellular uptake experiments to evaluate TfR1-mediated internalization. To measure such cellular uptake mediated by antibodies, the anti-TfR antibody was conjugated to several different DMPK-targeting oligonucleotides, and the conjugate were labeled with Cypher5e, a pH-sensitive dye. Rhabdomyosarcoma (RD) cells were treated for 4 hours with 100 nM of the conjugates, trypsinized, washed twice, and analyzed by flow cytometry. Mean Cypher5e fluorescence (representing uptake) was calculated using Attune NxT software. As shown in  FIG.  25   , the anti-TfR antibody show endosomal uptake. Similar internalization efficiency were observed for different oligonucleotide payloads. An anti-mouse TfR antibody was used as the negative control. Cold (non-internalizing) conditions abrogated the fluorescence signal of the positive control antibody-conjugate (data not shown), indicating that the positive signal in the positive control and humanized anti-TfR Fab-conjugates is due to internalization of the Fab-conjugates. 
     The activity of the conjugate containing the anti-TfR antibody and the DMPK-targeting oligonucleotide (control DMPK-ASO) in knocking down DMPK mRNA level in RD cells was also tested. The results showed that the conjugated achieved dose-dependent knock down of DMPK mRNA level ( FIG.  26   ). 
     The results demonstrate that the anti-TfR1 antibody bind to TfR1 on muscles with high affinity, can mediate the internalized of a conjugated molecular payload (e.g., oligonucleotide) and that the molecular payload (DMPK-targeting oligonucleotide) are able to target and knockdown the target gene (DMPK). Molecular payloads targeting other genes can also be conjugated to the anti-TfR antibody described herein and used to target other genes specifically in muscle cells. 
     Example 19. Serum Stability of the Linker Linking the Anti-TfR Antibody and the Molecular Payload 
     Oligonucleotides which were linked to antibodies in examples were conjugated via a cleavable linker shown in Formula (C). It is important that the linker maintain stability in serum and provide release kinetics that favor sufficient payload accumulation in the targeted muscle cell. This serum stability is important for systemic intravenous administration, stability of the conjugated oligonucleotide in the bloodstream, delivery to muscle tissue and internalization of the therapeutic payload in the muscle cells. The linker has been confirmed to facilitate precise conjugation of multiple types of payloads (including ASOs, siRNAs and PMOs) to Fabs. This flexibility enabled rational selection of the appropriate type of payload to address the genetic basis of each muscle disease. Additionally, the linker and conjugation chemistry allowed the optimization of the ratio of payload molecules attached to each Fab for each type of payload, and enabled rapid design, production and screening of molecules to enable use in various muscle disease applications. 
       FIG.  27    shows serum stability of the linker in vivo, which was comparable across multiple species over the course of 72 hours after intravenous dosing. At least 75% stability was measured in each case at 72 hours after dosing. 
     Example 20. Knockdown of DMPK mRNA Level Facilitated by Oligonucleotides Conjugates In Vitro 
     DMPK-targeting oligonucleotides (e.g., ASO) were tested in rhabdomyosarcoma (RD) cells for knockdown of DMPK transcript expression. RD cells were cultured in a growth medium of DMEM with glutamine, supplemented with 10% FBS and penicillin/streptomycin until nearly confluent. Cells were then seeded into a 96 well plate at 20K cells per well and were allowed to recover for 24 hours. Cells were then treated with free DMPK-targeting oligonucleotides or by transfection of the oligonucleotides using 0.3 μL per well of Lipofectamine MessengerMAX transfection reagent. After 3 days, total RNA was collected from cells, cDNA was synthesized and DPMK expression was measured by qPCR. 
     Results in  FIG.  28    show that DMPK expression level was reduced in cells treated with each given DMPK-targeting oligonucleotide, relative to expression in PBS-treated cells. Several DMPK-oligonucleotides showed dose-dependent reduction of DMPK expression level. In  FIG.  28   , DMPK-ASO-1 has the sequence GCGUAGAAGGGCGUCUGCCC (SEQ ID NO: 310). DMPK-ASO-2 has the sequence CCCAGCGCCCACCAGUCACA (SEQ ID NO: 320). DMPK-ASO-3 has the sequence CCAUCUCGGCCGGAAUCCGC (SEQ ID NO: 278). Control DMPK-ASO was also used in this experiment. 
     Example 21. Splicing Correction and Functional Efficacy in HSA-LR Mouse Model of DM1 
     Correction of splicing in the HSA-LR mouse model of DM1 was demonstrated with conjugates containing anti-TfR antibodies conjugated to oligonucleotides target human skeletal actin (ACTA1). The anti-TfR1 used in this study was RI7 217. The oligonucleotide targeting ACTA1 is a 2′-MOE 5-10-5 gapmer that comprises: 5′-NH 2 —(CH 2 ) 6 -dA*oC*oC*oA*oT*oT*dT*dTMCMT*dTMCMCMAMCMA*oG*oG*oG*oC*oT-3 (SEQ ID NO: 761); wherein ‘*’ represents a PS linkage; ‘d’ represents a deoxynucleic acid; and ‘o’ represents a 2′-MOE. 
     The HSA-LR DM1 mouse model is a well-validated model of DM1 that exhibits pathologies that are very similar to human DM1 patients. The HSA-LR model uses the human skeletal actin (ACTA1) promoter to drive expression of CUG long repeats (LR). In this model, toxic DMPK RNA accumulates within the nucleus and sequesters proteins responsible for splicing, such as Muscleblind-like protein (MBNL), resulting in mis-splicing of multiple RNAs, including CLCN1 (chloride channel), ATP2a1 (calcium channel), and others. This mis-splicing causes the mice to also exhibit myotonia which is a hallmark of the DM1 clinical presentation in humans. 
     The anti-TfR-oligonucleotide conjugate delivered intravenously has previously been shown to have activity in dose-dependent correction of splicing in multiple RNAs and multiple muscles and was well tolerated by HSA-LR mice. In this study, the ability of the conjugates to correct splicing in more than 30 different RNAs was evaluated. DM1, significant RNA mis-splicing of these RNAs reduces the ability of multiple muscles&#39; function. The RNAs monitored are critical for contraction and relaxation of muscle in HSA-LR mice. Dose-dependent correction of splicing was observed. 
       FIG.  29    shows results for Atp2a1, which encodes a calcium channel and contributes to muscle contraction and relaxation. The X-axis represents splice derangement with 1.00 representing severe mis-splicing and 0.00 representing a wild type (WT) splice pattern. Progression from right to left in the figure represents a correction of splicing. The Y-axis represents the percent of the gene spliced in (PSI). Severe mis-splicing of ATP2a1 is caused by exclusion of exon 22 in the ATP2a1 RNA. WT splicing reflects near complete inclusion of exon 22. Results demonstrate that the conjugate corrected splicing of ATP2a1 in a dose-dependent manner in the gastrocnemius muscle. 
     Data for the more than 30 different RNAs that were tested in this study are shown in  FIGS.  30 A- 30 C . Similar dose-dependent correction of splicing was achieved for all of the tested RNAs in gastrocnemius muscle. For some of these RNAs, correction of splicing is reflected by a decrease in PSI, as in  FIG.  29   , and for other RNAs correction is reflected by an increase in PSI. 
     Similar dose-dependent improvements in splicing within the set of RNAs were observed in the quadriceps and tibialis anterior muscles, after treatment with the conjugate.  FIG.  31    shows composite levels of splicing derangement observed for saline and different doses of the Ab-ASO across the more than 30 RNAs that were tested in each muscle type. Doses of 10 mg/kg and 20 mg/kg were administered in this study. 
     In addition to reductions in splicing derangement across multiple genes in several muscles in the HSA-LR model, disease modification was observed in the HSA-LR model. The results in  FIG.  32    show that almost complete reversal of myotonia was achieved after a single dose of the conjugate. The severity of myotonia on a four-point scale was evaluated 14 days following dosing with saline (PBS), naked oligonucleotide, or the conjugate. Grade 0 indicates no myotonia was observed, grade 1 indicates myotonic discharge was measured by electromyography (EMG) in less than 50% of needle insertions, grade 2 indicates myotonic discharge was measured in greater than 50% of needle insertions and grade 3 indicates myotonic discharge was measured with nearly every needle insertion. 
     Example 22. DMPK-Targeting PMOs 
     Additional DMPK targeting oligonucleotides (PMOs) were designed and tested for their activity in reducing DMPK expression in primary human myotubes. Wild-type primary myoblasts were cultured in PromoCell Skeletal Muscle growth medium with 5% FBS and penicillin/streptomycin until nearly confluent. Cells were then seeded into a 96 well plate at 50K cells per well and allowed to recover for 24 hours. Cells were then differentiated in a differentiation medium of DMEM with glutamine and penicillin/streptomycin for 7 days. Cells were then treated with the unconjugated PMO for 3 days. Total RNA was collected from cells, cDNA was synthesized and DPMK expression was measured by qPCR. The sequences of the PMOs and their activity in knocking down DMPK in vitro are shown in Table 16. 
     
       
         
           
               
             
               
                 TABLE 16 
               
             
            
               
                   
               
               
                 DMPK-targeting PMOs and activity in knocking down DMPK in vitro 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 % DMPK Knockdown 
               
               
                   
                   
                   
                 in Primary Human 
               
               
                 PMO# 
                 PMO Sequence 
                 Target region 
                 Myotubes 
               
               
                   
               
               
                  1 
                 CAGGTGACAGTTCAGGTGCAG 
                 intron 1-2 
                 59% 
               
               
                   
                 (SEQ ID NO: 778) 
                   
                   
               
               
                   
               
               
                  2 
                 TCCACCCTGACTCCAGGTGAC 
                 intron 1-2 
                 16% 
               
               
                   
                 (SEQ ID NO: 779) 
                   
                   
               
               
                   
               
               
                  3 
                 GAGAAGGAAATAAGACCCAGTT 
                 intron 1-2 
                 14% 
               
               
                   
                 (SEQ ID NO: 780) 
                   
                   
               
               
                   
               
               
                  4 
                 CCTTCTCTCTGCCTCTCAGCTT 
                 intron 1-2 
                 58% 
               
               
                   
                 (SEQ ID NO: 781) 
                   
                   
               
               
                   
               
               
                  5 
                 CCACCCTCTGTCTGTCTCC 
                 intron 1-2 
                 64% 
               
               
                   
                 (SEQ ID NO: 782) 
                   
                   
               
               
                   
               
               
                  6 
                 TCCGCTGGGTGGTGGGAAAAGAA 
                 Exon 2 
                  9% 
               
               
                   
                 (SEQ ID NO: 783) 
                   
                   
               
               
                   
               
               
                  7 
                 ATGGGCTCCGCTGGGTGGTGG 
                 Exon 2 
                 11% 
               
               
                   
                 (SEQ ID NO: 784) 
                   
                   
               
               
                   
               
               
                  8 
                 ACGATGGGCTCCGCTGGG 
                 Exon 2 
                 60% 
               
               
                   
                 (SEQ ID NO: 785) 
                   
                   
               
               
                   
               
               
                  9 
                 CCATCCTTGGGCAGAGACCT 
                 Intron 4-5 
                 41% 
               
               
                   
                 (SEQ ID NO: 786) 
                   
                   
               
               
                   
               
               
                 10 
                 ATGACCAGGTACTGAGAAGGG 
                 Exon 5 
                 33% 
               
               
                   
                 (SEQ ID NO: 787) 
                   
                   
               
               
                   
               
               
                 11 
                 AGGTACTGAGAAGGGTTCGTC 
                 Exon 5 
                 40% 
               
               
                   
                 (SEQ ID NO: 788) 
                   
                   
               
               
                   
               
               
                 12 
                 TAGGGACCTGCGGAGAGGGCGA 
                 Exon 15 
                 35% 
               
               
                   
                 (SEQ ID NO: 789) 
                   
                   
               
               
                   
               
               
                 13 
                 GCCTAGGGACCTGCGGGAGAG 
                 Exon 15 
                 62% 
               
               
                   
                 (SEQ ID NO: 790) 
                   
                   
               
               
                   
               
               
                 14 
                 GCCTTTTATTCGCGAGGGTCGG 
                 polyA 
                 73% 
               
               
                   
                 (SEQ ID NO: 791) 
                   
                   
               
               
                   
               
               
                 15 
                 TGGAGGGCCTTTTATTCGCGAGG 
                 polyA 
                 66% 
               
               
                   
                 (SEQ ID NO: 792) 
                   
                   
               
               
                   
               
               
                 39 
                 TAGGCACTCACCCACTGCAAGA 
                 Exon 1 
                 69% 
               
               
                   
                 (SEQ ID NO: 793) 
                   
                   
               
               
                   
               
               
                 40 
                 CGGAGCTCACCAGGTAGTTCT 
                 Intron 4-5 
                 73% 
               
               
                   
                 (SEQ ID NO: 794) 
                   
                   
               
               
                   
               
               
                 41 
                 AGGGCAGTGCTTACCTGAGGG 
                 Intron 9-10 
                 57% 
               
               
                   
                 (SEQ ID NO: 795) 
               
               
                   
               
            
           
         
       
     
     Example 23. In Vivo Activity of Anti-TfR Conjugates in hTfR1 Mice 
     In DM1, the higher than normal number of CUG repeats form large hairpin loops that remain trapped in the nucleus, forming nuclear foci that bind splicing proteins and inhibit the ability of splicing proteins to perform their normal function. When toxic nuclear DMPK levels are reduced, the nuclear foci are diminished, releasing splicing proteins, allowing restoration of normal mRNA processing, and potentially stopping or reversing disease progression. 
     The in vivo activity of conjugates containing an anti-TfR Fab′ (a control anti-TfR Fab′ or an anti-TfR Fab′ comprising a HC of SEQ ID NO: 777 and a LC of SEQ ID NO: 212) conjugated to the DMPK-targeting oligonucleotide (control DMPK-ASO) in reducing DMPK mRNA level in multiple muscle tissues following systemic intravenous administration in mice was evaluated. 
     Male and female C57BL/6 mice where one TfR1 allele was replaced with a human TFR1 allele were administered between the ages of 5 and 15 weeks according to the dosing schedule outlined in Table 17. Mice were sacrificed 14 days after the first injection and selected muscles collected as indicated in Table 18. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 17 
               
               
                   
               
               
                   
                   
                   
                   
                 Dose 
                 Dose 
                   
                 Terminal 
               
               
                   
                 Animal 
                 Treatment 
                 Treatment 
                 Level 
                 Volume 
                 Dosing 
                 Time 
               
               
                 Group 
                 No. 
                 Antibody 
                 Oligo 
                 (mg/kg) 
                 (mL/kg) 
                 Regimen 
                 Point 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 1 
                 4 
                 Vehicle 
                 NA 
                 0 
                 10 
                 Day 0 
                 Day 14 
               
               
                 2 
                 4 
                 NA 
                 control 
                 10 
                 5.0 
                 and Day 
               
               
                   
                   
                   
                 DMPK- 
                   
                   
                 7 by IV 
               
               
                   
                   
                   
                 ASO 
               
               
                 3 
                 4 
                 control anti- 
                 control 
                   
                 10.2 
               
               
                   
                   
                 TfR Fab′ 
                 DMPK- 
               
               
                   
                   
                   
                 ASO 
               
               
                 4 
                 4 
                 anti-TfR 
                 control 
                   
                 9.1 
               
               
                   
                   
                 having HC of 
                 DMPK- 
               
               
                   
                   
                 SEQ ID NO: 
                 ASO 
               
               
                   
                   
                 777 and LC 
               
               
                   
                   
                 of SEQ ID 
               
               
                   
                   
                 NO: 212 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 18 
               
               
                   
                   
               
               
                   
                 Tissue 
                 Storage 
               
               
                   
                   
               
             
            
               
                   
                 Gastrocnemius 
                 Right leg of each animal stored 
               
               
                   
                   
                 in RNALater at −80° C. 
               
               
                   
                 Tibialis 
                 One leg (R) of each animal stored 
               
               
                   
                 Anterior 
                 in RNALater at −80° C. 
               
               
                   
                 Heart 
                 Dissect transversally and store 
               
               
                   
                   
                 the apex in RNAlater at −80° C. 
               
               
                   
                 Diaphragm 
                 Split in half and collect one 
               
               
                   
                   
                 half in RNAlater at −80° C. 
               
               
                   
                   
               
            
           
         
       
     
     Total RNA was extracted on a Maxwell Rapid Sample Concentrator (RSC) Instrument using kits provided by the manufacturer (Promega). Purified RNA was reverse-transcribed and levels of Drnpk and Ppib transcripts determined by qRT-PCR with specific TaqMan assays (ThermoFlsher). Log fold changes in Drnpk expression were calculated according to the 2 −ΔΔCT  method using Ppib as the reference gene and mice injected with vehicle as the control group. Statistical significance in differences of Dmpk expression between control mice and mice administered with the conjugates were determined by one-way ANOVA with Dunnet&#39;s correction for multiple comparisons. As shown in  FIGS.  33 A- 33 D , the tested conjugates showed robust activity in reducing DMPK mRNA level in vivo in various muscle tissues. 
     Example 24. In Vitro Activity of Anti-TfR Conjugates in Patient-Derived Cells 
     An in vitro experiment was conducted to determine the activities of anti-TfR conjugates in reducing DMPK mRNA expression, correcting BIN1 splicing, and reducing nuclear foci in CM-DM1-32F primary cells expressing a mutant DMPK mRNA containing 380 GTG repeats. The CM-DM1-32F primary cell is an immortalized myoblastic cell line isolated from a DM1 patient (CL5 cells; Described in Arandel et al.,  Dis Model Mech.  2017 Apr. 1; 10(4): 487-497). Conjugate 1 contains an anti-TfR mAb conjugated to DMPK-targeting oligonucleotide, control DMPK-ASO. Conjugate 2 contains an anti-TfR Fab′ conjugated to DMPK ASO-1 (GCGUAGAAGGGCGUCUGCCC; SEQ ID NO: 310). 
     CL5 cells were seeded at a density of 156,000 cells/cm 2 , allowed to recover for 24 hours, transferred to differentiation media to induce myotube formation, as described (Arandel et al.) and subsequently exposed to conjugate 1 and conjugate 2 at a payload concentration of 500 nM. Parallel cultures exposed to vehicle PBS served as controls. Cells were harvested after 10 days of culture. 
     For analysis of gene expression, cells were collected with Qiazol for total RNA extraction with a Qiagen miRNAeasy kit. Purified RNA was reverse-transcribed and levels of DMPK, PPIB, BIN1 transcripts and of the BIN1 mRNA isoform containing exon 11 determined by qRT-PCR with specific TaqMan assays (ThermoFlsher). Log fold changes in DMPK expression were calculated according to the 2 −ΔΔCT  method using PPIB as the reference gene and cells exposed to vehicle as the control group. Log fold changes in the levels BIN1 isoform containing exon 11 were calculated according to the 2 −ΔΔCT  method using BIN1 as the reference gene and cells exposed to vehicle as the control group. 
     To measure the area of mutant DMPK nuclear foci, cells were fixed in 4% formalin, permeabilized with 0.1% Triton X-100 and hybridized at 70° C. with a CAG peptide-nucleic acid probe conjugated to the Cy5 fluorophore. After multiple washes in hybridization buffer and 2×SSC solution, nuclei were counterstained with DAPI. Images were collected at a 400× magnification by confocal microscopy and foci area measured as the area of Cy5 signal contained within the area of DAPI signal. Data were expressed as foci area corrected for nuclear area. 
     The results show that a single dose of the conjugates containing an anti-TfR (IgG or Fab′) conjugated to a DMPK-targeting oligonucleotide (control DMPK-ASO or DMPK ASO-1 (SEQ ID NO: 310)) resulted reduced mutant DMPK expression ( FIG.  34 A ), corrected BIN1 splicing ( FIG.  34 B ), and reduced nuclear foci by approximately 40% ( FIG.  34 C ). 
     Additional Embodiments 
     1. A complex comprising a muscle-targeting agent covalently linked to a molecular payload configured for inhibiting expression or activity of a DMPK allele comprising a disease-associated-repeat, wherein the muscle-targeting agent specifically binds to an internalizing cell surface receptor on muscle cells, 
     wherein the muscle targeting agent is an antibody that binds to a transferrin receptor and comprises a heavy chain variable region (VH) comprising a CDR-H1, a CDR-H2, and a CDR-H3 of any one of the antibodies listed in Table 2, Table 4, or Table 7, and/or a light chain variable region (VL) comprising a CDR-L1, a CDR-L2, and a CDR-L3 of any one of the antibodies listed in Table 2, Table 4, or Table 7. 
     2. The complex of embodiment 1, wherein the antibody comprises a VH that is at least 85% identical to the VH of any one of the antibodies listed in Table 2 or Table 7, and/or a VL that is at least 85% identical to the VL of any one of the antibodies listed in Table 2 or Table 7. 
     3. The complex of embodiment 1, wherein the antibody is selected from: 
     (i) an antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 7, and/or a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 8; 
     (ii) an antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 15, and/or a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 16; 
     (iii) an antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 23, and/or a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 24; and 
     (iv) an antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 of a VH comprising the amino acid sequence of SEQ ID NO: 204, and/or a CDR-L1, a CDR-L2, and a CDR-L3 of a VL comprising the amino acid sequence of SEQ ID NO: 205. 
     4. The complex of embodiment 1, wherein the antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 1, a CDR-H2 of SEQ ID NO: 2, SEQ ID NO: 731, or SEQ ID NO: 80, a CDR-H3 of SEQ ID NO: 3, a CDR-L1 of SEQ ID NO: 4, a CDR-L2 of SEQ ID NO: 5, and a CDR-L3 of SEQ ID NO: 6; 
     (ii) a CDR-H1 of SEQ ID NO: 145, a CDR-H2 of SEQ ID NO: 146, SEQ ID NO: 732, or SEQ ID NO: 734, a CDR-H3 of SEQ ID NO: 147, a CDR-L1 of SEQ ID NO: 148, a CDR-L2 of SEQ ID NO: 149, and a CDR-L3 of SEQ ID NO: 6; or 
     (iii) a CDR-H1 of SEQ ID NO: 150, a CDR-H2 of SEQ ID NO: 151, SEQ ID NO: 739, or SEQ ID NO: 740, a CDR-H3 of SEQ ID NO: 152, a CDR-L1 of SEQ ID NO: 153, a CDR-L2 of SEQ ID NO: 5, and a CDR-L3 of SEQ ID NO: 154. 
     5. The complex of embodiment 1, wherein the antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 10, a CDR-H3 of SEQ ID NO: 11, a CDR-L1 of SEQ ID NO: 12, a CDR-L2 of SEQ ID NO: 13, and a CDR-L3 of SEQ ID NO: 14; 
     (ii) a CDR-H1 of SEQ ID NO: 155, a CDR-H2 of SEQ ID NO: 156, a CDR-H3 of SEQ ID NO: 157, a CDR-L1 of SEQ ID NO: 158, a CDR-L2 of SEQ ID NO: 159, and a CDR-L3 of SEQ ID NO: 14; or 
     (iii) a CDR-H1 of SEQ ID NO: 160, a CDR-H2 of SEQ ID NO: 161, a CDR-H3 of SEQ ID NO: 162, a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 13, and a CDR-L3 of SEQ ID NO: 164. 
     6. The complex of embodiment 1, wherein the antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 17, SEQ ID NO: 735, or SEQ ID NO: 737, a CDR-H2 of SEQ ID NO: 18, a CDR-H3 of SEQ ID NO: 19, a CDR-L1 of SEQ ID NO: 20, a CDR-L2 of SEQ ID NO: 21, and a CDR-L3 of SEQ ID NO: 22; 
     (ii) a CDR-H1 of SEQ ID NO: 165, SEQ ID NO: 736, or SEQ ID NO: 738, a CDR-H2 of SEQ ID NO: 166, a CDR-H3 of SEQ ID NO: 167, a CDR-L1 of SEQ ID NO: 168, a CDR-L2 of SEQ ID NO: 169, and a CDR-L3 of SEQ ID NO: 22; or 
     (iii) a CDR-H1 of SEQ ID NO: 170, a CDR-H2 of SEQ ID NO: 171, a CDR-H3 of SEQ ID NO: 172, a CDR-L1 of SEQ ID NO: 173, a CDR-L2 of SEQ ID NO: 21, and a CDR-L3 of SEQ ID NO: 174. 
     7. The complex of embodiment 8, wherein the antibody comprises: 
     (i) a CDR-H1 of SEQ ID NO: 188, a CDR-H2 of SEQ ID NO: 189, a CDR-H3 of SEQ ID NO: 190, a CDR-L1 of SEQ ID NO: 191, a CDR-L2 of SEQ ID NO: 192, and a CDR-L3 of SEQ ID NO: 193; 
     (ii) a CDR-H1 of SEQ ID NO: 194, a CDR-H2 of SEQ ID NO: 195, a CDR-H3 of SEQ ID NO: 196, a CDR-L1 of SEQ ID NO: 197, a CDR-L2 of SEQ ID NO: 198, and a CDR-L3 of SEQ ID NO: 193; or 
     (iii) a CDR-H1 of SEQ ID NO: 199, a CDR-H2 of SEQ ID NO: 200, a CDR-H3 of SEQ ID NO: 201, a CDR-L1 of SEQ ID NO: 202, a CDR-L2 of SEQ ID NO: 192, and a CDR-L3 of SEQ ID NO: 203. 
     8. The complex of any one of embodiments 1-7, wherein the antibody is selected from: 
     (i) an antibody comprising a VH comprising an amino acid sequence at least 85% identical to SEQ ID NO: 7, and/or a VL comprising an amino acid sequence at least 85% identical to SEQ ID NO: 8; 
     (ii) an antibody comprising a VH comprising an amino acid sequence at least 85% identical to SEQ ID NO: 15, and/or a VL comprising an amino acid sequence at least 85% identical to SEQ ID NO: 16; 
     (iii) an antibody comprising a VH comprising an amino acid sequence at least 85% identical to SEQ ID NO: 23, and/or a VL comprising an amino acid sequence at least 85% identical to SEQ ID NO: 24; 
     (iv) an antibody comprising a VH comprising an amino acid sequence at least 85% identical to SEQ ID NO: 204, and/or a VL comprising an amino acid sequence at least 85% identical to SEQ ID NO: 205. 
     9. The complex of any one of embodiments 1 to 8, wherein the equilibrium dissociation constant (K D ) of binding of the antibody to the transferrin receptor is in a range from 10 −11 M to 10 −6  M. 
     10. The complex of any one of embodiments 1 to 9, wherein the antibody does not specifically bind to the transferrin binding site of the transferrin receptor and/or wherein the antibody does not inhibit binding of transferrin to the transferrin receptor. 
     11. The complex of any one of embodiments 1 to 10, wherein the antibody is cross-reactive with extracellular epitopes of two or more of a human, non-human primate and rodent transferrin receptor. 
     12. The complex of any one of embodiments 1 to 11, wherein the complex is configured to promote transferrin receptor mediated internalization of the molecular payload into a muscle cell. 
     13. The complex of any one of embodiments 1 to 12, wherein the antibody is a chimeric antibody, optionally wherein the chimeric antibody is a humanized monoclonal antibody. 
     14. The complex of any one of embodiments 1 to 13, wherein the antibody is in the form of a ScFv, Fab fragment, Fab′ fragment, F(ab′) 2  fragment, or Fv fragment. 
     15. The complex of any one of embodiments 1 to 14, wherein the molecular payload is an oligonucleotide. 
     16. The complex of embodiment 15, wherein the oligonucleotide comprises at least 15 consecutive nucleotides of a sequence comprising any one of SEQ ID NOs: 246-481 and 778-795. 
     17. The complex of embodiment 16, wherein the oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 246-481 and 778-795. 
     18. The complex of embodiment 17, wherein the oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 257, 260, 270, 272, 278, 280, 286, 288, 293, 294, 299, 301, 310, 313, 316, 320, 346, and 362. 
     19. The complex of embodiment 18, wherein the oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 278, 310, and 320. 
     20. The complex of any one of embodiments 1-14, wherein the oligonucleotide comprises a region of complementarity to any one of SEQ ID NO: 482-717. 
     21. The complex of embodiment 20, wherein the oligonucleotide comprises a region of complementarity to at least 15 consecutive nucleotides of any one of SEQ ID NO: 482-717. 
     22. The complex of any one of embodiments 15 to 21, wherein the oligonucleotide comprises a region of complementarity to the DMPK allele comprising the disease-associated-repeat expansion. 
     23. The complex of any one of embodiments 1 to 14, wherein the molecular payload is a polypeptide. 
     24. The complex of embodiment 23, wherein the polypeptide is a muscleblind-like (MBNL) polypeptide. 
     25. The complex of any one of embodiments 15 to 22, wherein the oligonucleotide comprises an antisense strand that hybridizes, in a cell, with a wild-type DMPK mRNA transcript encoded by the allele, wherein the DMPK mRNA transcript comprises repeating units of a CUG trinucleotide sequence. 
     26. The complex of any one of embodiments 15 to 22, wherein the oligonucleotide comprises an antisense strand that hybridizes, in a cell, with a mutant DMPK mRNA transcript encoded by the allele, wherein the DMPK mRNA transcript comprises repeating units of a CUG trinucleotide sequence. 
     27. The complex of any one of embodiments 1 to 26, wherein the disease-associated-repeat is 38 to 200 repeating units in length. 
     28. The complex of embodiment 27, wherein the disease-associated-repeat is associated with late onset myotonic dystrophy. 
     29. The complex of any one of embodiments 1 to 26, wherein the disease-associated-repeat is 100 to 10,000 repeat units in length. 
     30. The complex of embodiment 29, wherein the disease-associated-repeat is associated with congenital myotonic dystrophy. 
     31. The complex of any one of embodiments 15 to 22 and 25 to 30, wherein the oligonucleotide comprises at least one modified internucleotide linkage. 
     32. The complex of embodiment 31, wherein the at least one modified internucleotide linkage is a phosphorothioate linkage. 
     33. The complex of embodiment 32, wherein the oligonucleotide comprises phosphorothioate linkages in the Rp stereochemical conformation and/or in the Sp stereochemical conformation. 
     34. The complex of embodiment 33, wherein the oligonucleotide comprises phosphorothioate linkages that are all in the Rp stereochemical conformation or that are all in the Sp stereochemical conformation. 
     35. The complex of any one of embodiments 15 to 22 and 25 to 34, wherein the oligonucleotide comprises one or more modified nucleotides. 
     36. The complex of embodiment 35, wherein the one or more modified nucleotides are 2′-modified nucleotides. 
     37. The complex of any one of embodiments 15 to 22 and 25 to 36, wherein the oligonucleotide is a gapmer oligonucleotide that directs RNAse H-mediated cleavage of a DMPK mRNA transcript in a cell. 
     38. The complex of embodiment 37, wherein the gapmer oligonucleotide comprises a central portion of 5 to 15 deoxyribonucleotides flanked by wings of 2 to 8 modified nucleotides. 
     39. The complex of embodiment 38, wherein the modified nucleotides of the wings are 2′-modified nucleotides. 
     40. The complex of any one of embodiments 15 to 22 and 25 to 36, wherein the oligonucleotide is a mixmer oligonucleotide. 
     41. The complex of embodiment 40, wherein the mixmer oligonucleotide inhibits binding of muscleblind-like protein 1, muscleblind-like protein 2, or muscleblind-like protein 3 to the DMPK mRNA transcript. 
     42. The complex of embodiment 40 or 41, wherein the mixmer oligonucleotide comprises two or more different 2′ modified nucleotides. 
     43. The complex of any one of embodiments 15 or 22 and 25 to 36, wherein the oligonucleotide is an RNAi oligonucleotide that promotes RNAi-mediated cleavage of the DMPK mRNA transcript. 
     44. The complex of embodiment 43, wherein the RNAi oligonucleotide is a double-stranded oligonucleotide of 19 to 25 nucleotides in length. 
     45. The complex of embodiment 43 or 44, wherein the RNAi oligonucleotide comprises at least one 2′ modified nucleotide. 
     46. The complex of any one of embodiments 36, 39, 42, or 45, wherein each 2′ modified nucleotide is selected from the group consisting of: 2′-O-methyl, 2′-fluoro (2′-F), 2′-O-methoxyethyl (2′-MOE), and 2′, 4′-bridged nucleotides. 
     47. The complex of embodiment 35, wherein the one or more modified nucleotides are bridged nucleotides. 
     48. The complex of any one of embodiment 36, 39, 42, or 45, wherein at least one 2′ modified nucleotide is a 2′,4′-bridged nucleotide selected from: 2′,4′-constrained 2′-O-ethyl (cEt) and locked nucleic acid (LNA) nucleotides. 
     49. The complex of any one of embodiments 15 to 22 and 25 to 36, wherein the oligonucleotide comprises a guide sequence for a genome editing nuclease. 
     50. The complex of any one of embodiments 15 to 22 and 25 to 36, wherein the oligonucleotide is phosphorodiamidite morpholino oligomer. 
     51. The complex of any one of embodiments 1 to 50, wherein the muscle-targeting agent is covalently linked to the molecular payload via a cleavable linker. 
     52. The complex of embodiment 51, wherein the cleavable linker is selected from: a protease-sensitive linker, pH-sensitive linker, and glutathione-sensitive linker. 
     53. The complex of embodiment 52, wherein the cleavable linker is a protease-sensitive linker. 
     54. The complex of embodiment 53, wherein the protease-sensitive linker comprises a sequence cleavable by a lysosomal protease and/or an endosomal protease. 
     55. The complex of embodiment 53, wherein the protease-sensitive linker comprises a valine-citrulline dipeptide sequence. 
     56. The complex of embodiment 52, wherein the linker is pH-sensitive linker that is cleaved at a pH in a range of 4 to 6. 
     57. The complex of any one of embodiments 1 to 50, wherein the muscle-targeting agent is covalently linked to the molecular payload via a non-cleavable linker. 
     58. The complex of embodiment 57, wherein the non-cleavable linker is an alkane linker. 
     59. The complex of any of embodiments 2 to 58, wherein the antibody comprises a non-natural amino acid to which the oligonucleotide is covalently linked. 
     60. The complex of any of embodiments 2 to 58, wherein the antibody is covalently linked to the oligonucleotide via conjugation to a lysine residue or a cysteine residue of the antibody. 
     61. The complex of embodiment 60, wherein the antibody is conjugated to the cysteine via a maleimide-containing linker, optionally wherein the maleimide-containing linker comprises a maleimidocaproyl or maleimidomethyl cyclohexane-1-carboxylate group. 
     62. The complex of any one of embodiments 2 to 61, wherein the antibody is a glycosylated antibody that comprises at least one sugar moiety to which the oligonucleotide is covalently linked. 
     63. The complex of embodiment 62, wherein the sugar moiety is a branched mannose. 
     64. The complex of embodiment 62 or 63, wherein the antibody is a glycosylated antibody that comprises one to four sugar moieties each of which is covalently linked to a separate oligonucleotide. 
     65. The complex of embodiment 62, wherein the antibody is a fully-glycosylated antibody. 
     66. The complex of embodiment 62, wherein the antibody is a partially-glycosylated antibody. 
     67. The complex of embodiment 66, wherein the partially-glycosylated antibody is produced via chemical or enzymatic means. 
     68. The complex of embodiment 66, wherein the partially-glycosylated antibody is produced in a cell, cell that is deficient for an enzyme in the N- or O-glycosylation pathway. 
     69. A method of delivering a molecular payload to a cell expressing transferrin receptor, the method comprising contacting the cell with the complex of any one of embodiments 1 to 68. 
     70. A method of inhibiting activity of DMPK in a cell, the method comprising contacting the cell with the complex of any one of embodiments 1 to 68 in an amount effective for promoting internalization of the molecular payload to the cell. 
     71. The method of embodiment 70, wherein the cell is in vitro. 
     72. The method of embodiment 70, wherein the cell is in a subject. 
     73. The method of embodiment 72, wherein the subject is a human. 
     74. The method of any one of embodiments 70 to 73, wherein the complex inhibits the expression of DMPK. 
     75. The method of any one of embodiments 70 to 74, wherein the cell is contacted with a single dose of the complex. 
     76. The method of embodiment 75, wherein a single dose of the complex inhibits the expression of DMPK for at least two, four, eight, or twelve weeks. 
     77. The method of embodiment 76, wherein the complex inhibits the expression of DMPK by at least 30%, 40%, 50%, or 60% relative to a control. 
     78. The method of embodiment 76 or 77, the complex inhibits the expression of DMPK in muscle tissues by 40-60% for at least 12 weeks following administration of the single dose, relative to a control 
     79. A method of treating a subject having an expansion of a disease-associated-repeat of a DMPK allele that is associated with myotonic dystrophy, the method comprising administering to the subject an effective amount of the complex of any one of embodiments 1 to 68. 
     80. The method of embodiment 79, wherein the disease-associated-repeat comprises repeating units of a trinucleotide sequence. 
     81. The method of embodiment 79, wherein the trinucleotide sequence is a CTG trinucleotide sequence. 
     82. The method of any one of embodiments 79 to 81, wherein the disease-associated-repeat is 38 to 200 repeating units in length. 
     83. The embodiment of 82, wherein the disease-associated-repeat is associated with late onset myotonic dystrophy. 
     84. The method of any one of embodiments 79 to 81, wherein the disease-associated-repeat is 100 to 10,000 repeating units in length. 
     85. The method of embodiment 84, wherein the disease-associated-repeat is associated with congenital myotonic dystrophy. 
     86. The method of any one of embodiments 79 to 85, wherein administration of the complex results in inhibition of the expression of DMPK in muscle tissues. 
     87. The method of any one of embodiments 79 to 86, wherein the complex is intravenously administered to the subject. 
     88. The method of any one of embodiments 79 to 87, wherein an effective amount of the complex comprises 1-15 mg/kg of RNA. 
     89. The method of any one of embodiments 79 to 88, wherein the complex is administered to the subject in a single dose. 
     90. The method of embodiment 89, wherein administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues for at least two, four, eight, or twelve weeks. 
     91. The method of embodiment 90, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues by at least 30%, 40%, 50%, or 60% relative to a control. 
     92. The method of embodiment 90 or 91, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues for at least 12 weeks following administration of the single dose. 
     93. The method of embodiment 92, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues by 40-60%, relative to a control, for at least 12 weeks following administration of the single dose. 
     94. The method of embodiment 90 or 91, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues for a duration of time in the range of 4-8, 5-10, 8-12, 10-14, or 8-16 weeks following administration of the single dose. 
     95. The method of embodiment 94, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues by 40-60%, relative to a control, for a duration of time in the range of 4-8, 5-10, 8-12, 10-14, or 8-16 weeks following administration of the single dose. 
     96. The method of embodiment 90 or 91, wherein the administration of a single dose of the complex results in inhibition of the expression of DMPK in muscle tissues by 40-60%, relative to a control, at 12 weeks following administration of the single dose. 
     97. The method of any one of embodiments 79 to 88, wherein the complex is administered to the subject in a single dose once every 4-8, 5-10, 8-12, or 8-16 weeks. 
     98. The method of embodiment 97, wherein the complex is administered to the subject in a single dose once every 12 weeks. 
     99. The method of any one of embodiments 89 to 98, wherein the single dose comprises the complex at a concentration of 1-15 mg/kg of RNA. 
     100. The method of embodiment 99, wherein the single dose comprises the complex at a concentration of 10 mg/kg of RNA. 
     101. A method of treating a subject having an expansion of a disease-associated-repeat of a DMPK allele that is associated with myotonic dystrophy, the method comprising administering the complex of any one of embodiments 1 to 68 to the subject, wherein the administration results in inhibition of DMPK expression in muscle tissues by 40-60%, relative to a control, for a duration of time in the range of 4-8, 5-10, 8-12, 10-14, or 8-16 weeks following administration of the complex. 
     102. A method of inhibiting DMPK expression in a subject, the method comprising administering the complex of any one of embodiments 1 to 68, wherein the administration results in inhibition of DMPK expression in muscle tissues by 40-60%, relative to a control, for a duration of time in the range of 4-8, 5-10, 8-12, 10-14, or 8-16 weeks following administration of the complex. 
     103. The method of embodiment 101 or 102, wherein the molecular payload is an oligonucleotide. 
     104. The method of embodiment 103, wherein the concentration of the complex is 1-15 mg/kg of RNA. 
     Equivalents and Terminology 
     The disclosure illustratively described herein suitably can be practiced in the absence of any element or elements, limitation or limitations that are not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of”, and “consisting of” may be replaced with either of the other two terms. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the disclosure. Thus, it should be understood that although the present disclosure has been specifically disclosed by preferred embodiments, optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this disclosure. 
     In addition, where features or aspects of the disclosure are described in terms of Markush groups or other grouping of alternatives, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group or other group. 
     It should be appreciated that, in some embodiments, sequences presented in the sequence listing may be referred to in describing the structure of an oligonucleotide or other nucleic acid. In such embodiments, the actual oligonucleotide or other nucleic acid may have one or more alternative nucleotides (e.g., an RNA counterpart of a DNA nucleotide or a DNA counterpart of an RNA nucleotide) and/or (e.g., and) one or more modified nucleotides and/or (e.g., and) one or more modified internucleotide linkages and/or (e.g., and) one or more other modification compared with the specified sequence while retaining essentially same or similar complementary properties as the specified sequence. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Embodiments of this invention are described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. 
     The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.