Patent Publication Number: US-2022227866-A1

Title: Anti-ror1 / anti-cd3 bispecific binding molecules

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application 62/852,039, filed May 23, 2019. The disclosure of that priority application is incorporated by reference herein in its entirety. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing that has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. The electronic copy of the Sequence Listing, created on May 18, 2020, is named 024651_WO004_SL.txt and is 258,844 bytes in size. 
     BACKGROUND OF THE INVENTION 
     Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a cell surface protein that mediates signals from its ligand, the secreted glycoprotein Wnt5a. Consistent with its role in influencing the fate of stem cells during embryogenesis, ROR1 expression is observed on invasive malignancies that revert to an embryonic transcriptional program, but is not observed on normal adult tissues, offering a favorable selectivity profile as a therapeutic target. ROR1 is commonly expressed on the malignant cells of patients with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphoblastic leukemia (CLL), mantle cell lymphoma (MCL), follicular lymphoma (FL), marginal zone lymphoma (MZL), diffuse large B-cell lymphoma (DLBCL), and Richter&#39;s transformation or Richter&#39;s syndrome (RS). ROR1 is also present on the cell surfaces of multiple solid tumors, where it appears to be a marker of cancer stem cells. Because it is not expressed to appreciable levels in healthy adult tissues, but displays high levels of expression in multiple hematological and solid tumors, ROR1 is an attractive target for tumor-specific therapy. 
     Cluster of differentiation 3 (CD3) is a multimeric protein complex expressed on T cells in association with the T cell receptor complex (TCR), and is required for T cell activation. Functional CD3 is formed from the dimeric association of two of four distinct chains—epsilon, gamma, delta, and zeta—into one of the following three pairs of dimers: gamma/epsilon, delta/epsilon and zeta/zeta. Antibodies against CD3 have been shown to cluster CD3 on T cells, causing T cell activation. Accordingly, anti-CD3 antibodies have been proposed for therapeutic purposes involving the activation of T cells. For example, bispecific antibodies that are capable of binding CD3 and a target antigen have been proposed for therapeutic uses involving targeting T cell immune responses to tissues and cells expressing the target antigen. Recent approval of the CD19 x CD3 bispecific T-cell engager (BiTE), blinatumomab, has validated this approach. 
     Numerous formats and compositions have been described for bispecific binding molecules. Multiple variables impact the in vivo potency of these molecules, including PK, targeted antigen epitopes, the relative affinities of the antigen-binding components, and the valency and spatial configuration of the paratopes. Currently, there is no reliable method for designing apriori a single molecule that optimizes all these parameters for a bispecific binding molecule, such as an antibody that specifically binds to both ROR1 and CD3. Bispecific constructs must be designed, made, and tested to systematically evaluate the impact of many of these parameters and to select optimal bispecific binding molecules for therapeutic uses such as cancer treatment. 
     In view of the above, there is a need for new and improved cancer therapeutics that combine the tumor specificity of the ROR1 antigen with the potent activity of redirected T cells. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to novel bispecific binding molecules targeting ROR1 and CD3, as well as pharmaceutical compositions comprising one or more of these antibodies, and use of the antibodies and pharmaceutical compositions for treating cancer. Compared to currently available cancer treatments, including antibody treatments, it is contemplated that the bispecific binding molecules of the invention may provide a superior clinical response. 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising a first antigen-binding domain that specifically binds to an extracellular domain of human ROR1 and a second antigen-binding domain that specifically binds to an extracellular domain of human CD3. 
     In certain embodiments, the first antigen-binding domain competes for binding to human ROR1 with, or binds to the same epitope of human ROR1 as, an antibody comprising a heavy chain amino acid sequence set forth in SEQ ID NO: 82 and a light chain amino acid sequence set forth in SEQ ID NO: 83. In particular embodiments, the first antigen-binding domain comprises: 
     a) heavy chain (H)-CDR1-3 and light chain (L)-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively;
 
b) H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively;
 
c) a heavy chain variable domain (VH) comprising an amino acid sequence at least 90% identical to SEQ ID NO: 72 and a light chain variable domain (VL) comprising an amino acid sequence at least 90% identical to SEQ ID NO: 73;
 
d) a VH comprising the amino acid sequence of SEQ ID NO: 74 and a VL comprising the amino acid sequence of SEQ ID NO: 73;
 
e) a VH comprising the amino acid sequence of SEQ ID NO: 72 and a VL comprising the amino acid sequence of SEQ ID NO: 73;
 
f) a heavy chain (HC) comprising the amino acid sequence of SEQ ID NO: 84 and a light chain (LC) comprising the amino acid sequence of SEQ ID NO: 83;
 
g) an HC comprising the amino acid sequence of SEQ ID NO: 82 and an LC comprising the amino acid sequence of SEQ ID NO: 83;
 
h) an HC comprising the amino acid sequence of SEQ ID NO: 87 and an LC comprising the amino acid sequence of SEQ ID NO: 83; or
 
i) an HC comprising the amino acid sequence of SEQ ID NO: 86 and an LC comprising the amino acid sequence of SEQ ID NO: 83.
 
     In certain embodiments, the second antigen-binding domain competes for binding to human CD3 with, or binds to the same epitope of human CD3 as, an antibody that comprises: 
     a) a heavy chain variable domain (VH) comprising the amino acid sequence of SEQ ID NO: 70 and a light chain variable domain (VL) comprising the amino acid sequence of SEQ ID NO: 71;
 
b) a VH comprising the amino acid sequence of SEQ ID NO: 66 and a VL comprising the amino acid sequence of SEQ ID NO: 67; or
 
c) a VH comprising the amino acid sequence of SEQ ID NO: 68 and a VL comprising the amino acid sequence of SEQ ID NO: 69. In particular embodiments, the second antigen-binding domain comprises:
 
a) heavy chain (H)-CDR1-3 and light chain (L)-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;
 
b) H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;
 
c) H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs. 47, 53, 49, 50, 51, and 52, respectively;
 
d) a heavy chain variable domain (VH) comprising an amino acid sequence at least 90% identical to SEQ ID NO: 70 and a light chain variable domain (VL) comprising an amino acid sequence at least 90% identical to SEQ ID NO: 71;
 
e) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO: 66 and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO: 67;
 
f) a VH comprising an amino acid sequence at least 90% identical to SEQ ID NO: 68 and a VL comprising an amino acid sequence at least 90% identical to SEQ ID NO: 69;
 
g) a VH comprising the amino acid sequence of SEQ ID NO: 70 and a VL comprising the amino acid sequence of SEQ ID NO: 71;
 
h) a VH comprising the amino acid sequence of SEQ ID NO: 66 and a VL comprising the amino acid sequence of SEQ ID NO: 67;
 
i) a VH comprising the amino acid sequence of SEQ ID NO: 68 and a VL comprising the amino acid sequence of SEQ ID NO: 69;
 
j) a VH comprising the amino acid sequence of SEQ ID NO: 80 and a VL comprising the amino acid sequence of SEQ ID NO: 81;
 
k) a VH comprising the amino acid sequence of SEQ ID NO: 76 and a VL comprising the amino acid sequence of SEQ ID NO: 77; or
 
l) a VH comprising the amino acid sequence of SEQ ID NO: 78 and a VL comprising the amino acid sequence of SEQ ID NO: 79.
 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising: 
     a) a first antigen-binding domain that comprises heavy chain (H)-CDR1-3 and light chain (L)-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;
 
b) a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;
 
c) a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;
 
d) a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;
 
e) a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively; or
 
f) a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively.
 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising: 
     a) a first antigen-binding domain that comprises a heavy chain variable domain (VH) and a light chain variable domain (VL) comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
b) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
c) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;
 
d) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;
 
e) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively; or
 
f) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively.
 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising: 
     a) a first antigen-binding domain that comprises a heavy chain variable domain (VH) and a light chain variable domain (VL) comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
b) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
c) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively;
 
d) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively;
 
e) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively; or
 
f) a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively.
 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising: 
     a) a first antigen-binding domain that comprises a heavy chain (HC) and a light chain (LC) comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
b) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
c) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;
 
d) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;
 
e) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;
 
f) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;
 
g) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
h) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;
 
i) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;
 
j) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;
 
k) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69, respectively; or
 
l) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67, respectively.
 
     In some embodiments, the present disclosure provides a bispecific binding molecule comprising: 
     a) a first antigen-binding domain that comprises a heavy chain (HC) and a light chain (LC) comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
b) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
c) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively;
 
d) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively;
 
e) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively;
 
f) a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively;
 
g) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
h) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 80 and 81, respectively;
 
i) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively;
 
j) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively;
 
k) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 78 and 79, respectively; or
 
l) a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106 or 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 76 and 77, respectively.
 
     In certain embodiments, a bispecific binding molecule of the present disclosure comprises the amino acid sequences of SEQ ID NOs: 14 and 19, SEQ ID NOs: 7 and 19, SEQ ID NOs: 7 and 18, or SEQ ID NOs: 7 and 23. In certain embodiments, a bispecific binding molecule of the present disclosure comprises: 
     a) the amino acid sequences of SEQ ID NOs: 1 and 16;
 
b) the amino acid sequences of SEQ ID NOs: 2 and 16;
 
c) the amino acid sequences of SEQ ID NOs: 3 and 16;
 
d) the amino acid sequences of SEQ ID NOs: 4 and 16;
 
e) the amino acid sequences of SEQ ID NOs: 5 and 16;
 
f) the amino acid sequences of SEQ ID NOs: 6 and 16;
 
g) the amino acid sequences of SEQ ID NOs: 7 and 17;
 
h) the amino acid sequences of SEQ ID NOs: 7 and 20;
 
i) the amino acid sequences of SEQ ID NOs: 7 and 21;
 
j) the amino acid sequences of SEQ ID NOs: 7 and 22;
 
k) the amino acid sequences of SEQ ID NOs: 8, 9, and 16;
 
l) the amino acid sequences of SEQ ID NOs: 8, 10, and 16;
 
m) the amino acid sequences of SEQ ID NOs: 8, 11, and 16;
 
n) the amino acid sequences of SEQ ID NOs: 12, 11, and 16;
 
o) the amino acid sequences of SEQ ID NOs: 12, 13, and 16; or
 
p) the amino acid sequences of SEQ ID NOs: 8, 15, and 16.
 
     In some embodiments, a bispecific binding molecule described herein may have any of the following valencies for the first and second antigen-binding domains: 
     a) the first antigen-binding domain has a valency of 2 and the second antigen-binding domain has a valency of 2:
 
b) the first antigen-binding domain has a valency of 1 and the second antigen-binding domain has a valency of 1; or
 
c) the first antigen-binding domain has a valency of 2 and the second antigen-binding domain has a valency of 1.
 
     In some embodiments, a bispecific binding molecule described herein may comprise a human IgG1 constant region; said constant region may contain the amino acid substitutions L234A, L235A, and/or G237A, wherein the residues are numbered according to the EU system. 
     In some embodiments, the second antigen-binding domain of a bispecific binding molecule described herein is an scFv. 
     In some embodiments of a bispecific binding molecule described herein, a heavy or light chain amino acid sequence of the second antigen-binding domain is fused to a heavy or light chain amino acid sequence of the first antigen-binding domain via a peptide linker. In certain embodiments, the peptide linker has the amino acid sequence of GGGGSGGGGS (SEQ ID NO: 93). In particular embodiments, the heavy or light chain amino acid sequence of the second antigen-binding domain may be fused to, e.g.: 
     a) the carboxy-terminus of the light chain of the first antigen-binding domain; or
 
b) the amino-terminus of the light chain of the first antigen-binding domain.
 
     In certain embodiments, a bispecific binding molecule described herein has at least one (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12) of the following properties: 
     a) has a K D  for immobilized ROR1 of 0.5 nM or less as determined by ELISA;
 
b) has a K D  for soluble b-ROR1 of 0.4 nM or less as determined by ELISA;
 
c) demonstrates reduced internalization in ROR1-transfected MEC cells and/or Jurkat cells as compared to an antibody comprising the heavy and light chain amino acid sequences of SEQ ID NOs: 82 and 83, respectively;
 
d) induces LDH release in PBMC-exposed ROR1-transfected MEC cells at 1 μg/mL or less;
 
e) induces LDH release in PBMC-exposed JeKo-1 cells at 1 μg/mL or less;
 
f) induces LDH release in PBMC-exposed Mino cells at 1 μg/mL or less;
 
g) induces LDH release in PBMC-exposed MDA-MB-468 cells at 1 μg/mL or less;
 
h) upregulates CD69 on the surface of T cells co-cultured with ROR1-transfected MEC cells at 1 μg/mL or less as determined by flow cytometry;
 
i) upregulates CD69 on the surface of T cells co-cultured with JeKo-1 cells at 1 μg/mL or less as determined by flow cytometry;
 
j) upregulates CD69 on the surface of T cells co-cultured with Mino cells at 1 μg/mL or less as determined by flow cytometry;
 
k) upregulates CD69 on the surface of T cells co-cultured with MDA-MB-468 cells at 1 μg/mL or less as determined by flow cytometry; and
 
l) induces release of IFN-γ, TNF-α, IL-10, IL-6, IL-4, and IL-2 from T cells co-cultured with Jeko-1 or ROR1-transfected MEC cells at 1 μg/mL or less.
 
     The present disclosure also provides an immunoconjugate comprising a bispecific binding molecule described herein conjugated to a cytotoxic agent. 
     The present disclosure also provides a pharmaceutical composition comprising a bispecific binding molecule described herein and a pharmaceutically acceptable excipient. 
     The present disclosure also provides one or more isolated nucleic acid molecules comprising nucleotide sequences that encode the heavy and light chain variable domains (VH and VL) of the first antigen-binding domain, and further comprising nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule described herein. In some embodiments, the isolated nucleic acid molecule(s) comprise: 
     a) the nucleotide sequences of SEQ ID NOs: 37 and 42;
 
b) the nucleotide sequences of SEQ ID NOs: 30 and 42;
 
c) the nucleotide sequences of SEQ ID NOs: 30 and 41;
 
d) the nucleotide sequences of SEQ ID NOs: 30 and 46;
 
e) the nucleotide sequences of SEQ ID NOs: 24 and 39;
 
f) the nucleotide sequences of SEQ ID NOs: 25 and 39;
 
g) the nucleotide sequences of SEQ ID NOs: 26 and 39;
 
h) the nucleotide sequences of SEQ ID NOs: 27 and 39;
 
i) the nucleotide sequences of SEQ ID NOs: 28 and 39;
 
j) the nucleotide sequences of SEQ ID NOs: 29 and 39;
 
k) the nucleotide sequences of SEQ ID NOs: 30 and 40;
 
l) the nucleotide sequences of SEQ ID NOs: 30 and 43;
 
m) the nucleotide sequences of SEQ ID NOs: 30 and 44;
 
n) the nucleotide sequences of SEQ ID NOs: 30 and 45;
 
o) the nucleotide sequences of SEQ ID NOs: 31, 32, and 39;
 
p) the nucleotide sequences of SEQ ID NOs: 31, 33 and 39;
 
q) the nucleotide sequences of SEQ ID NOs: 31, 34, and 39;
 
r) the nucleotide sequences of SEQ ID NOs: 35, 34, and 39;
 
s) the nucleotide sequences of SEQ ID NOs: 35, 36, and 39; or
 
t) the nucleotide sequences of SEQ ID NOs: 31, 38, and 39.
 
     The present disclosure also provides a vector comprising isolated nucleic acid molecule(s) described herein. 
     The present disclosure also provides a host cell comprising nucleotide sequences that encode the heavy and light chain variable domains (VH and VL) of the first antigen-binding domain, and further comprising nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule described herein. In some embodiments, the host cell comprises the nucleotide sequences of: 
     a) SEQ ID NOs: 37 and 42; 
     b) SEQ ID NOs: 30 and 42; 
     c) SEQ ID NOs: 30 and 41; 
     d) SEQ ID NOs: 30 and 46; 
     e) SEQ ID NOs: 24 and 39; 
     f) SEQ ID NOs: 25 and 39; 
     g) SEQ ID NOs: 26 and 39; 
     h) SEQ ID NOs: 27 and 39; 
     i) SEQ ID NOs: 28 and 39; 
     j) SEQ ID NOs: 29 and 39; 
     k) SEQ ID NOs: 30 and 40; 
     l) SEQ ID NOs: 30 and 43; 
     m) SEQ ID NOs: 30 and 44; 
     n) SEQ ID NOs: 30 and 45; 
     o) SEQ ID NOs: 31, 32, and 39; 
     p) SEQ ID NOs: 31, 33 and 39; 
     q) SEQ ID NOs: 31, 34, and 39; 
     r) SEQ ID NOs: 35, 34, and 39; 
     s) SEQ ID NOs: 35, 36, and 39; or 
     t) SEQ ID NOs: 31, 38, and 39. 
     The present invention also provides a method for producing a bispecific binding molecule described herein, comprising providing a host cell as described herein, cultivating said host cell under conditions suitable for expression of the bispecific binding molecule, and isolating the resulting bispecific binding molecule. 
     The present disclosure also provides a method for treating cancer in a patient, comprising administering to the patient a bispecific binding molecule described herein. Further, the present disclosure provides the use of a bispecific binding molecule described herein for the manufacture of a medicament for treating cancer in a patient, and a bispecific binding molecule described herein for use in treating cancer in a patient. In some embodiments, the cancer is a ROR1-positive cancer. In some embodiments, the cancer is a leukemia, a lymphoma, or a solid tumor. In some embodiments, the cancer is acute myeloid leukemia, acute lymphoblastic leukemia, chronic lymphocytic leukemia, T-cell leukemia, mantle cell lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, Burkitt&#39;s lymphoma, T cell non-Hodgkin lymphoma, lymphoplasmacytoid lymphoma, Waldenström macroglobulinemia, multiple myeloma, marginal zone lymphoma, small lymphocytic lymphoma, or a non-Hodgkin lymphoma that has undergone Richter&#39;s transformation. In some embodiments, the cancer is colon cancer, non-small cell lung cancer, glioblastoma, hepatocellular carcinoma, pancreatic cancer, Ewing sarcoma, osteosarcoma, head and neck cancer, ovarian cancer, breast cancer, or triple negative breast cancer. In certain embodiments, the patient may be treated with one or more additional therapeutic agents, such as a Bruton&#39;s tyrosine kinase (BTK) inhibitor, a B-cell lymphoma 2 (Bcl-2) inhibitor, a mammalian target of rapamycin (mTOR) inhibitor, and/or a phosphoinositide 3-kinase (PI3K) inhibitor. In particular embodiments, the additional therapeutic agent is ibrutinib, acalabrutinib, venetoclax, everolimus, sapanisertib, or idelalisib. 
     The present disclosure also provides a kit comprising a bispecific binding molecule as described herein. Further, the present disclosure provides an article of manufacture comprising a bispecific binding molecule as described herein, wherein said article of manufacture is suitable for treating cancer in a patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating exemplary configurations of bispecific binding molecules of the present disclosure. 
         FIG. 2  is a pair of graphs illustrating the binding to human ROR1 of a parental Ab1 Fab (WT) and three heavy chain variants (Ab2 (T32A), Ab3 (T32E), and W110Y), as determined by ELISA (Panel A) and by flow cytometry analysis of binding to live ROR1-transfected MEC cells (Panel B). 
         FIG. 3  is a graph illustrating the binding to human ROR1 of a parental Ab1 Fab (WT) and three variants (Ab2 (T32A), Ab6 (T32A (HC)+A25P (LC)), and Ab7 (T32A (HC)+T69R (LC))), as determined by ELISA using prolonged wash conditions. 
         FIG. 4  is a pair of graphs showing the selectivity of bispecific constructs 1-3, 7-9, and 13-15 for ROR1, as demonstrated by flow cytometry analysis of binding to ROR1-transfected MEC cells (Panel A) and control MEC cells (Panel B). Non-specific human IgG was included as a control (“Control”). 
         FIG. 5  is a set of graphs showing the influence of ROR1 expression levels on binding of bispecific constructs 1-3, 7-9, and 13-15 (Panel A), 4-6 and 10-12 (Panel B), and 3, 9, and 15-20 (Panel C). Binding was assessed by flow cytometry using JeKo-1 cells, which express lower levels of ROR1 (˜13,000 copies/cell) than ROR1-transfected MEC cells (˜56,000 copies/cell). 
         FIG. 6  is a pair of graphs showing the binding of bispecific constructs to immobilized human ROR1 as characterized by ELISA. 
         FIG. 7  is a graph showing the binding of bispecific constructs to soluble, biotinylated human ROR1 as characterized by ELISA. 
         FIG. 8  is a set of graphs showing cell surface levels of bispecific binding molecules bound to ROR1 (“Surface biAb”), cell surface levels of free ROR1 not bound by bispecific binding molecules (“Unoccupied epitope”), and total cell surface ROR1 (“Total ROR1”), for ROR1-transfected MEC cells incubated with construct 1 (Panel A), construct 7 (Panel B), and construct 13 (Panel C). 
         FIG. 9  is a pair of graphs showing cell surface levels of bispecific binding molecules bound to ROR1 (“Surface biAb”), cell surface levels of free ROR1 not bound by bispecific binding molecules (“Unoccupied epitope”), and total cell surface ROR1 (“Total ROR1”), for ROR1-transfected MEC cells incubated with construct 19 (Panel A) and construct 20 (Panel B). 
         FIG. 10  is a graph showing quantitation of bispecific constructs 1, 7, and 13 on the surface of ROR-1 transfected MEC cells after incubation for 24 h. 
         FIG. 11  is a set of graphs illustrating the binding to Jurkat cells of bispecific constructs 1-6 (Panel A), 7-12 (Panel B), and 13-15 (Panel C) as demonstrated by flow cytometry analysis. Non-specific human IgG was included as a control (“Control”). 
         FIG. 12  is a pair of graphs illustrating the binding to Jurkat cells of bispecific constructs 1, 7, and 13 (Panel A), and bispecific constructs 3, 9, and 15-10 (Panel B), as demonstrated by flow cytometry analysis. Non-specific human IgG was included as a control in one experiment (Panel A, “Control”) while an unrelated ROR1 x CD3 bispecific construct (U.S. Patent Publication 2017/0233472) was included as a control in the second experiment (Panel B, “control 1”). 
         FIG. 13  is a graph quantitating levels of bispecific constructs 1-3, 7-9, and 13-15 on the surface of Jurkat cells over time following binding to CD3 in the absence of ROR1. 
         FIG. 14  is a pair of graphs quantitating LDH release from ROR1-transfected MEC cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where ROR1-transfected MEC cells are incubated with (1) human PBMCs, and (2) bispecific constructs 1, 3, 7, 9, 13, and 15, and a control anti-CD19/anti-CD3 bispecific binding molecule (“CD19 x CD3”). 
         FIG. 15  is a pair of graphs quantitating LDH release from ROR1-transfected MEC cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where ROR1-transfected MEC cells are incubated with human PBMCs and bispecific constructs 3, 9, and 15-20. 
         FIG. 16  is a graph comparing LDH release between ROR1-transfected and non-transfected MEC cells incubated with (1) PBMCs, and (2) bispecific constructs 1-3, 7-9, and 13-15 and an anti-CD19/anti-CD3 bispecific binding molecule control. LDH release is also assessed in samples that did not contain target cells (“PBMC”) and samples that did not contain a bispecific construct (“no biAb”). 
         FIG. 17  is a set of graphs assessing CD69 levels on T cells, where ROR1-/CD19 +  MEC cells (Panel A) or ROR1*/CD19 +  MEC cells (Panel B) are incubated with (1) the T cells, and (2) bispecific construct 7 or a control anti-CD19/anti-CD3 bispecific binding molecule (“CD19 x CD3”). 
         FIG. 18  is a pair of graphs quantitating LDH release from JeKo-1 cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where JeKo-1 cells are incubated with human PBMCs and bispecific constructs 2, 3, 8, 9, 14, and 15. 
         FIG. 19  is a pair of graphs quantitating LDH release from JeKo-1 cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where JeKo-1 cells are incubated with human PBMCs and bispecific constructs 3, 7, 9, and 15-20. 
         FIG. 20  is a pair of graphs quantitating LDH release from Mino cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where Mino cells are incubated with human PBMCs and bispecific constructs 7-9. 
         FIG. 21  is a pair of graphs quantitating LDH release from MDA-MB-468 cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where MDA-MB-468 cells are incubated with human PBMCs and bispecific constructs 2, 3, 8, 9, 12, and 14. 
         FIG. 22  is a pair of graphs quantitating LDH release from MDA-MB-468 cells (Panel A) and cell surface levels of CD69 on CD8 +  cells (Panel B), where MDA-MB-468 cells are incubated with human PBMCs and bispecific constructs 9, 18, and 20. 
         FIG. 23  is a set of graphs quantitating release of TNF-α from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, 20 (Panels B and C). Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 24  is a set of graphs quantitating release of IFN-γ from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, and 20 (Panels B and C). Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 25  is a set of graphs quantitating release of IL-2 from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, and 20 (Panels B and C). Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 26  is a set of graphs quantitating release of IL-4 from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, and 20 (Panels B and C). Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 27  is a set of graphs quantitating release of IL-6 from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, and 20 (Panels B and C) Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 28  is a set of graphs quantitating release of IL-10 from JeKo-1 cells (Panel A), ROR1-transfected MEC cells (Panel B), and from mock-transfected, ROR1 − MEC cells (Panel C) following activation of T cells with designated target cells and bispecific constructs 7, 9, 18, and 20 (Panel A) or 9, 18, and 20 (Panels B and C). Mock-transfected, ROR1 − MEC cells (Panel C) were treated with a single concentration (1 μg/mL) of the bispecific constructs. “Control 1” is an unrelated ROR1 x CD3 bispecific construct. 
         FIG. 29  is a table showing SEQ ID NOs for the indicated sequences of anti-ROR1 and anti-CD3 antigen-binding domains. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure provides new bispecific binding molecules that bind to ROR and CD3. In some embodiments, binding of the bispecific binding molecules to ROR and CD3 brings T cells in proximity to ROR1-positive tumor cells, thus treating cancer by invoking T cell cytotoxicity. Unless otherwise stated, as used herein, “ROR1” refers to human RORL. A human ROR1 polypeptide sequence is available under UniProt Accession No. Q01973-1 (SEQ ID NO: 89). Unless otherwise stated, as used herein, “CD3” refers to human CD3. CD3 is comprised of a gamma chain, a delta chain, and two epsilon chains. A human CD3 gamma polypeptide sequence is available under GenBank Accession Number NP_000064.1 (SEQ ID NO: 90). A human CD3 delta polypeptide sequence is available under GenBank Accession Number NP_000723.1 (SEQ ID NO: 91). A human CD3 epsilon polypeptide sequence is available under GenBank Accession Number NP_000724.1 (SEQ ID NO: 92). 
     In some embodiments, the antigen-binding domains of a bispecific binding molecule of the present disclosure are derived from an anti-ROR1 antibody and an anti-CD3 antibody. The term “antibody” (Ab) or “immunoglobulin” (Ig), as used herein, may refer to a tetramer comprising two heavy (H) chains (about 50-70 kDa) and two light (L) chains (about 25 kDa) interconnected by disulfide bonds. Each heavy chain is comprised of a heavy chain variable domain (VH) and a heavy chain constant region (CH). Each light chain is composed of a light chain variable domain (VL) and a light chain constant region (CL). The VH and VL domains can be subdivided further into regions of hypervariability, termed “complementarity determining regions” (CDRs), interspersed with regions that are more conserved, termed “framework regions” (FRs). Each VH and VL is composed of three CDRs (H-CDR herein designates a CDR from the heavy chain; and L-CDR herein designates a CDR from the light chain) and four FRs, arranged from amino-terminus to carboxyl-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. 
     The precise amino acid sequence boundaries of a given CDR or FR can be readily determined using any of several well-known schemes, including those described by Kabat et al., 5th Ed., Public Health Service, National Institutes of Health, Bethesda, Md. (1991) (“Kabat” numbering scheme); Al-Lazikani et al.,  JMB  273,927-948 (1997) (“Chothia” numbering scheme); MacCallum et al.,  J. Mol. Biol.  262:732-745 (1996) (“contact” numbering scheme); Lefranc et al.,  Dev Comp Immunol.  27(1):55-77 (2003) (“IMGT” numbering scheme); and Honegger and Plückthun,  J Mol Biol,  309(3):657-70 (2001) (“Aho” numbering scheme). 
     The boundaries of a given CDR or FR may vary depending on the scheme used for identification. For example, the Kabat scheme is based on sequence alignments, while the Chothia scheme is based on structural information. Numbering for both the Kabat and Chothia schemes is based upon the most common antibody region sequence lengths, with insertions accommodated by insertion letters, for example, “30a.” The two schemes place certain insertions and deletions (“indels”) at different positions, resulting in differential numbering. The contact scheme is based on analysis of complex crystal structures and is similar in many respects to the Chothia numbering scheme. Unless indicated otherwise, the CDRs of the antibodies referred to herein may be identified according to any of the Kabat, Chothia, IMGT, contact, and Aho methods. 
     In some embodiments, the anti-ROR1 antibody and/or the anti-CD3 antibody from which a bispecific binding molecule of the present disclosure is derived are monoclonal antibodies. In some embodiments, the anti-ROR1 and/or anti-CD3 antibodies are chimeric, humanized, or fully human antibodies. 
     The term “affinity” refers to a measure of the attraction between an antigen and an antibody or an antigen-binding fragment thereof, or a related molecule such as a bispecific binding molecule. The intrinsic attractiveness of the antibody for the antigen is typically expressed as the binding affinity equilibrium constant (K D ) of a particular antibody-antigen interaction. An antibody is said to specifically bind to an antigen when the K D  is ≤1 mM, preferably ≤100 nM. A K D  binding affinity constant can be measured, e.g., by surface plasmon resonance (BIAcore™) or Bio-Layer Interferometry, for example using the IBIS MX96 SPR system from IBIS Technologies or the Octet™ system from ForteBio. 
     The term “paratope” refers to the antigen-binding site of an antibody (i.e., the part of the antibody that recognizes and binds to an antigen epitope). 
     The term “epitope” as used herein refers to a portion (determinant) of an antigen that specifically binds to an antibody or a related molecule such as a bispecific binding molecule. Epitopic determinants generally consist of chemically active surface groupings of molecules such as amino acids or carbohydrate or sugar side chains and generally have specific three-dimensional structural characteristics, as well as specific charge characteristics. An epitope may be “linear” or “conformational.” In a linear epitope, all of the points of interaction between a protein (e.g., an antigen) and an interacting molecule (such as an antibody) occur linearly along the primary amino acid sequence of the protein. In a conformational epitope, the points of interaction occur across amino acid residues on the protein that are separated from one another in the primary amino acid sequence. Once a desired epitope on an antigen is determined, it is possible to generate antibodies to that epitope using techniques well known in the art. For example, an antibody to a linear epitope may be generated, e.g., by immunizing an animal with a peptide having the amino acid residues of the linear epitope. An antibody to a conformational epitope may be generated, e.g., by immunizing an animal with a mini-domain containing the relevant amino acid residues of the conformational epitope. An antibody to a particular epitope can also be generated, e.g., by immunizing an animal with the target molecule of interest (e.g., ROR1 or CD3) or a relevant portion thereof, then screening for binding to the epitope. 
     One can determine whether an antibody binds to the same epitope of ROR1 or CD3 as or competes for binding with a bispecific binding molecule of the present disclosure by using methods known in the art, including, without limitation, competition assays, epitope binning, and alanine scanning. In one embodiment, one allows the bispecific binding molecule of the present disclosure to bind to ROR1 or CD3 under saturating conditions, and then measures the ability of the test antibody to bind to said antigen. If the test antibody is able to bind to said antigen at the same time as the reference bispecific binding molecule, then the test antibody binds to a different epitope than the reference bispecific binding molecule. However, if the test antibody is not able to bind to the antigen at the same time, then the test antibody binds to the same epitope, an overlapping epitope, or an epitope that is in close proximity to the epitope bound by the bispecific binding molecule of the present disclosure. This experiment can be performed using, e.g., ELISA, RIA, BIACORE™, SPR, Bio-Layer Interferometry or flow cytometry. To test whether a bispecific binding molecule of the present disclosure cross-competes with another antibody for binding to ROR1 or CD3, one may use the competition method described above in two directions, i.e., determining if the known antibody blocks the test antibody and vice versa. Such cross-competition experiments may be performed, e.g., using an IBIS MX96 SPR instrument or the Octet™ system. 
     The term “antigen-binding portion” or “antigen-binding fragment” of an antibody, as used herein, refers to one or more portions or fragments of an antibody that retain the ability to specifically bind to an antigen (e.g., human ROR1 or CD3, or a portion thereof). It has been shown that certain fragments of a full-length antibody can perform the antigen-binding function of the antibody. Examples of binding fragments encompassed within the term “antigen-binding portion” include (i) a Fab fragment: a monovalent fragment consisting of the V L , V H , C L  and C H 1 domains; (ii) a F(ab′) 2  fragment: a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) an Fd fragment consisting of the V H  and C H 1 domains; (iv) a Fv fragment consisting of the V L  and V H  domains of a single arm of an antibody, (v) a dAb fragment, which consists of a V H  domain; and (vi) an isolated complementarity determining region (CDR) capable of specifically binding to an antigen. Furthermore, although the two domains of the Fv fragment, V L  and V H , are encoded by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the V L  and V H  domains pair to form monovalent molecules (known as single chain variable fragments (scFv)). Also within the present disclosure are antigen-binding molecules comprising a V H  and/or a V L . In the case of a V H , the molecule may also comprise one or more of a CH1, hinge, CH2, or CH3 region. Such single chain antibodies are also intended to be encompassed within the term “antigen-binding portion” of an antibody. Other forms of single chain antibodies, such as diabodies, are also encompassed. Diabodies are bivalent, bispecific antibodies in which V H  and V L  domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen-binding sites. 
     Unless otherwise indicated, all antibody amino acid residue numbers referred to in this disclosure are those under the Honegger numbering scheme (Honegger and Pluckthun,  J Mol Biol,  309(3):657-70 (2001)). 
     Anti-ROR1/Anti-CD3 Bispecifc Binding Molecules 
     The present disclosure relates to a bispecific binding molecule comprising a first antigen-binding domain that specifically binds to an extracellular domain of human ROR1 and a second antigen-binding domain that specifically binds to an extracellular domain of human CD3. 
     In some embodiments, the first antigen-binding domain binds to an epitope on an extracellular portion of the ROR1 protein such as an epitope in one or more of the immunoglobulin (Ig)-like, Frizzled, and Kringle domains. In certain embodiments, the first antigen-binding domain binds to an amino acid sequence of ROR1 shown in SEQ ID NO: 94 or 95 (not including the terminal cysteine, which is added for convenience of conjugation). 
     In some embodiments, the first antigen-binding domain competes for binding to human ROR1 with, and/or binds to the same epitope of human ROR1 as, an anti-ROR1 antibody described in PCT Patent Application PCT/US2013/32572. In some embodiments, the first antigen-binding domain competes for binding to human ROR1 with, and/or binds to the same epitope of human ROR1 as, an antibody comprising a heavy chain amino acid sequence set forth in SEQ ID NO: 82 and a light chain amino acid sequence set forth in SEQ ID NO: 83 (“Ab1”). 
     In some embodiments, the first antigen-binding domain comprises the heavy chain (H)-CDR1-3 in the amino acid sequence of SEQ ID NO: 82 and the light chain (L)-CDR1-3 in the amino acid sequence of SEQ ID NO: 83, wherein the CDRs are determined by the Kabat, Chothia, IMGT, or contact method, or any combination thereof. 
     In some embodiments, the first antigen-binding domain comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of:
         SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively;   SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively;   SEQ ID NOs: 98, 61, 62, 63, 64, and 65, respectively;   SEQ ID NOs: 60, 61, 62, 99, 64, 65, respectively;   SEQ ID NOs: 60, 61, 62, 63, 102, 65, respectively;   SEQ ID NOs: 97, 61, 62, 99, 64, 65, respectively;   SEQ ID NOs: 97, 61, 62, 63, 102, 65, respectively;   SEQ ID NOs: 98, 61, 62, 99, 64, 65, respectively; or   SEQ ID NOs: 98, 61, 62, 63, 102, 65, respectively.       

     In some embodiments, the first antigen-binding domain comprises a heavy chain variable domain (VH) comprising an amino acid sequence that is at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 72 and a light chain variable domain (VL) comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 73. 
     In some embodiments, the first antigen-binding domain comprises:
         a VH comprising the amino acid sequence of SEQ ID NO: 72 and a VL comprising the amino acid sequence of SEQ ID NO: 73;   a VH comprising the amino acid sequence of SEQ ID NO: 74 and a VL comprising the amino acid sequence of SEQ ID NO: 73;   a VH comprising the amino acid sequence of SEQ ID NO: 75 and a VL comprising the amino acid sequence of SEQ ID NO: 73;   a VH comprising the amino acid sequence of SEQ ID NO: 72 and a VL comprising the amino acid sequence of SEQ ID NO: 100;   a VH comprising the amino acid sequence of SEQ ID NO: 72 and a VL comprising the amino acid sequence of SEQ ID NO: 103;   a VH comprising the amino acid sequence of SEQ ID NO: 74 and a VL comprising the amino acid sequence of SEQ ID NO: 100;   a VH comprising the amino acid sequence of SEQ ID NO: 74 and a VL comprising the amino acid sequence of SEQ ID NO: 103;   a VH comprising the amino acid sequence of SEQ ID NO: 75 and a VL comprising the amino acid sequence of SEQ ID NO: 100; or   a VH comprising the amino acid sequence of SEQ ID NO: 75 and a VL comprising the amino acid sequence of SEQ ID NO: 103.       

     In some embodiments, the first antigen-binding domain comprises a heavy chain (HC) comprising an amino acid sequence that is at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 82 and a light chain (LC) comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 991%) identical to SEQ ID NO: 83. 
     In some embodiments, the first antigen-binding domain comprises:
         an HC comprising the amino acid sequence of SEQ ID NO: 82 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 84 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 85 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 82 and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 82 and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 84 and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 84 and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 85 and an LC comprising the amino acid sequence of SEQ ID NO: 101; or   an HC comprising the amino acid sequence of SEQ ID NO: 85 and an LC comprising the amino acid sequence of SEQ ID NO: 104.
 
In certain embodiments, the HC sequence is modified to reduce or eliminate effector function. For example, the IgG1 portion of the HC sequence may comprise “LALA” (L234A/L235A), or “LALAGA” (L234A/L235A/G237A) mutations (wherein all residues are numbered according to the EU numbering scheme).
       

     In some embodiments, the first antigen-binding domain comprises:
         an HC comprising the amino acid sequence of SEQ ID NO: 7 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 14 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 105 and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 7 and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 7 and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 14 and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 14 and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 105 and an LC comprising the amino acid sequence of SEQ ID NO: 101; or   an HC comprising the amino acid sequence of SEQ ID NO: 105 and an LC comprising the amino acid sequence of SEQ ID NO: 104.       

     In some embodiments, the first antigen-binding domain comprises:
         an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 101; or   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 104.       

     In some embodiments, the first antigen-binding domain comprises:
         an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83;   an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101;   an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104;   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101; or   an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO. 104.       

     In some embodiments, the first antigen-binding domain comprises the six CDRs, the heavy and light chain variable domains, and/or the heavy and light chain amino acid sequences of an anti-ROR1 antibody as described in PCT/US2013/32572. 
     In some embodiments, the second antigen-binding domain binds to a Group I or Group II epitope of CD3 as defined in Tunnacliffe et al.,  International Immunology  1:546-550 (1989)). 
     In some embodiments, the second antigen-binding domain competes for binding to human CD3 with, and/or binds to the same epitope of human CD3 as, anti-CD3 antibody OKT3 or SP34. In some embodiments, the second antigen-binding domain competes for binding to human CD3 with, and/or binds to the same epitope of human CD3 as, an antibody that comprises:
         a VH comprising the amino acid sequence of SEQ ID NO: 66 and a VL comprising the amino acid sequence of SEQ ID NO: 67;   a VH comprising the amino acid sequence of SEQ ID NO: 68 and a VL comprising the amino acid sequence of SEQ ID NO: 69; or   a VH comprising the amino acid sequence of SEQ ID NO: 70 and a VL comprising the amino acid sequence of SEQ ID NO: 71.       

     In some embodiments, the second antigen-binding domain comprises the H-CDR1-3 and L-CDR1-3 in the amino acid sequences of:
         SEQ ID NOs: 66 and 67, respectively;   SEQ ID NOs: 68 and 69, respectively; or   SEQ ID NOs: 70 and 71, respectively; wherein the CDRs are determined by the Kabat, Chothia, IMGT, or contact method, or any combination thereof.       

     In some embodiments, the second antigen-binding domain comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of:
         SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively; or   SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively.       

     In some embodiments, the second antigen-binding domain comprises:
         a VH comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 991%) identical to SEQ ID NO. 66 and a VL comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 67;   a VH comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 990%) identical to SEQ ID NO: 68 and a VL comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 69; or   a VH comprising an amino acid sequence that is at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 990%) identical to SEQ ID NO: 70 and a VL comprising an amino acid sequence at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to SEQ ID NO: 71.       

     In some embodiments, the second antigen-binding domain comprises:
         a VH comprising the amino acid sequence of SEQ ID NO: 66 and a VL comprising the amino acid sequence of SEQ ID NO: 67;   a VH comprising the amino acid sequence of SEQ ID NO: 68 and a VL comprising the amino acid sequence of SEQ ID NO: 69;   a VH comprising the amino acid sequence of SEQ ID NO: 70 and a VL comprising the amino acid sequence of SEQ ID NO: 71;   a VH comprising the amino acid sequence of SEQ ID NO: 76 and a VL comprising the amino acid sequence of SEQ ID NO: 77;   a VH comprising the amino acid sequence of SEQ ID NO: 78 and a VL comprising the amino acid sequence of SEQ ID NO: 79; or   a VH comprising the amino acid sequence of SEQ ID NO: 80 and a VL comprising the amino acid sequence of SEQ ID NO: 81.       

     In some embodiments, the second antigen-binding domain comprises the six CDRs and/or the heavy and light chain variable domains of an anti-CD3 antibody as described in U.S. Patent Publication 2018/0112011. 
     The present disclosure also contemplates any combination of the above-described first and second antigen-binding domains. 
     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1- and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 60, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 97, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 99, 64, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 54, 55, 56, 57, 58, and 59, respectively;   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 48, 49, 50, 51, and 52, respectively; or   a first antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 98, 61, 62, 63, 102, and 65, respectively, and a second antigen-binding domain that comprises H-CDR1-3 and L-CDR1-3 comprising the amino acid sequences of SEQ ID NOs: 47, 53, 49, 50, 51, and 52, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 990%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99° %) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%10) identical to the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99/%) identical to the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 990%) identical to the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 990%) identical to the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99° %) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99/%) identical to the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 70 and 71, respectively;   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 66 and 67, respectively; or   a first antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL at least 90% (e.g., at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identical to the amino acid sequences of SEQ ID NOs: 68 and 69, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 73, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 72 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 74 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 100, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively; or   a first antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 75 and 103, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 82 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 84 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively; or   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 85 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively.
 
In certain embodiments, the HC sequence is modified to reduce or eliminate effector function. For example, the IgG1 portion of the HC sequence may comprise L235E, “LALA” (L234A/L235A), or “LALAGA” (L234A/L235A/G237A) mutations (wherein all residues are numbered according to the EU numbering scheme).
       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 83, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 7 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 14 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 101, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively; or   a first antigen-binding domain that comprises an HC and an LC comprising the amino acid sequences of SEQ ID NOs: 105 and 104, respectively, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 106, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 107, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively; or   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 108, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 83, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 86, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 87, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 101, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 70 and 71 or 80 and 81, respectively;   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 66 and 67 or 76 and 77, respectively; or   a first antigen-binding domain that comprises an HC comprising the amino acid sequence of SEQ ID NO: 88, an HC comprising the amino acid sequence of SEQ ID NO: 109, and an LC comprising the amino acid sequence of SEQ ID NO: 104, and a second antigen-binding domain that comprises a VH and a VL comprising the amino acid sequences of SEQ ID NOs: 68 and 69 or 78 and 79, respectively.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises:
         the amino acid sequences of SEQ ID NOs: 1 and 16;   the amino acid sequences of SEQ ID NOs: 2 and 16;   the amino acid sequences of SEQ ID NOs: 3 and 16;   the amino acid sequences of SEQ ID NOs: 4 and 16;   the amino acid sequences of SEQ ID NOs: 5 and 16;   the amino acid sequences of SEQ ID NOs: 6 and 16;   the amino acid sequences of SEQ ID NOs: 7 and 17;   the amino acid sequences of SEQ ID NOs: 7 and 18;   the amino acid sequences of SEQ ID NOs: 7 and 19;   the amino acid sequences of SEQ ID NOs: 7 and 20;   the amino acid sequences of SEQ ID NOs: 7 and 21;   the amino acid sequences of SEQ ID NOs: 7 and 22;   the amino acid sequences of SEQ ID NOs: 8, 9, and 16;   the amino acid sequences of SEQ ID NOs: 8, 10, and 16;   the amino acid sequences of SEQ ID NOs: 8, 11, and 16;   the amino acid sequences of SEQ ID NOs: 12, 11, and 16;   the amino acid sequences of SEQ ID NOs: 12, 13, and 16;   the amino acid sequences of SEQ ID NOs: 14 and 19;   the amino acid sequences of SEQ ID NOs: 8, 15, and 16; or   the amino acid sequences of SEQ ID NOs: 7 and 23.       

     In some embodiments, a bispecific binding molecule of the present disclosure comprises one or two first antigen-binding domains as described above. In some embodiments, a bispecific binding molecule of the present disclosure comprises one or two second antigen-binding domains as described above. 
     In some embodiments, the first antigen-binding domain in a bispecific binding molecule of the present disclosure has a valency of 1 or 2. In some embodiments, the second antigen-binding domain in a bispecific binding molecule of the present disclosure has a valency of 1 or 2. Any combination of valencies of the first and second antigen-binding domains is contemplated; for example, the first and second antigen-binding domains may have valencies of 2 and 2, respectively; 1 and 1, respectively; 2 and 1, respectively; or 1 and 2, respectively. 
     In some embodiments, a bispecific binding molecule of the present disclosure may comprise a human IgG, IgM, IgE, IgA, or IgD constant region. In certain embodiments, the human constant region is of the IgG isotype, e.g., of IgG subclass IgG1, IgG2a or IgG2b, IgG3, or IgG4. In some embodiments, the bispecific binding molecule of the present disclosure may comprise a human a constant region. The class of a bispecific binding molecule described herein may be changed or switched with another class or subclass. For example, a constant region that was originally IgM may be class switched to IgG. Further, the class switching may be used to convert one IgG subclass to another, e.g., from IgG1 to IgG2. A u light chain constant region can be changed, e.g., to a λ light chain constant region. 
     In certain embodiments, a bispecific binding molecule of the present disclosure may comprise a human IgG constant region. In particular embodiments, the IgG constant region may include mutations that reduce or eliminate effector function (see, e.g., Wang et al.,  Protein Cell  9(1):63-73 (2018)). For example, a bispecific binding molecule of the present disclosure may comprise a human IgG1 constant region with the mutation L235E, “LALA” mutations (L234A/L235A), or “LALAGA” mutations (L234A/L235A/G237A), all numbered according to the EU numbering scheme). 
     The class (isotype) and subclass of bispecific binding molecules of the present disclosure may be determined by any method known in the art. In general, the class and subclass of an antibody may be determined using antibodies that are specific for a particular class and subclass of antibody. Such antibodies are available commercially. The class and subclass can be determined by ELISA, Western Blot as well as other techniques. Alternatively, the class and subclass may be determined by sequencing all or a portion of the constant regions of the heavy and/or light chains of the antibodies, comparing their amino acid sequences to the known amino acid sequences of various classes and subclasses of immunoglobulins, and determining the class and subclass of the antibodies. 
     In some embodiments, a bispecific binding molecule of the present disclosure is a homodimer. In some embodiments, a bispecific binding molecule of the present disclosure is a heterotrimer (light chain combined with heavy chain heterodimer), wherein the heavy chain heterodimer is, e.g., in a format described in Brinkmann and Kontermann,  MABS  9:182-212 (2017). For example, a “knobs-into-holes,” HA-TF, ZW1, CH3 charge pair, EW-RVT, LUZ-Y, Strand Exchange Engineered Domain body (SEEDbody), Biclonic, DuoBody, BEAT, 7.8.60, 20.8.34, Triomab/Quadroma, or CrossMAb strategy may be used to promote heterodimerization (e.g., over homodimerization) of the polypeptide comprising the Fc region of the immunoglobulin in the architecture of a bispecific binding molecule of the present disclosure. In certain embodiments, a “knobs-into-holes” approach may be used, wherein a “knob” variant of a domain is obtained by replacing an amino acid with a small side chain (for example, alanine, asparagine, aspartic acid, glycine, serine, threonine or valine) with another amino acid with a larger side chain (for example, arginine, phenylalanine, tyrosine, or tryptophan). A “hole” variant of a domain is obtained by replacing an amino acid with a large side chain (for example, arginine, phenylalanine, tyrosine, or tryptophan) with another amino acid with a smaller side chain (for example, alanine, asparagine, aspartic acid, glycine, serine, threonine or valine). In certain embodiments, the knob and/or hole mutations are in the CH3 domain. 
     In some embodiments, an antigen-binding fragment of an anti-ROR1 antibody and/or an antigen-binding fragment of an anti-CD3 antibody may be used in making a bispecific binding molecule of the present disclosure. Examples of antibody fragments include, but are not limited to, Fv, Fab, Fab′, Fab′-SH, F(ab′) 2 ; recombinant IgG (rIgG) fragments; diabodies; linear antibodies; single-chain antibody molecules (e.g., scFv or sFv); and single domain antibodies (e.g., sdAb, sdFv, nanobodies). In certain embodiments, the fragments are single-chain antibody fragments comprising a variable heavy chain region and/or a variable light chain region, such as scFvs. 
     In particular embodiments, the first antigen-binding domain, the second antigen-binding domain, or both, are single chain antibodies (scFv) comprising a heavy chain variable domain (VH) of an antibody linked to a light chain variable domain (VL) of the whole antibody, wherein the fusion protein retains the same antigen specificity as the antibody. The VH and VL may be linked via a peptide linker. In certain embodiments, the second antigen-binding domain is an scFv that specifically binds to CD3. 
     To create a single chain antibody (scFv), the VH- and VL-encoding DNA fragments are operatively linked to another fragment encoding a flexible linker, e.g., encoding the amino acid sequence (Gly4-Ser)4 (SEQ ID NO: 96), such that the VH and VL sequences can be expressed as a contiguous single-chain protein, with the VL and VH domains joined by the flexible linker. The single chain antibody may be monovalent, if only a single VH and VL are used; bivalent, if two VH and VL are used; or polyvalent, if more than two VH and VL are used. 
     In some embodiments, an amino acid sequence of the first antigen-binding domain is fused to an amino acid sequence of the second antigen-binding domain, e.g., via a peptide linker, to form a fusion polypeptide. In certain embodiments, the second antigen-binding domain is an scFv, and is fused to a heavy or light chain amino acid sequence of the first antigen-binding domain. For example, the second antigen-binding domain may be fused to:
         the amino-terminus of the heavy chain of the first antigen-binding domain;   the amino-terminus of the light chain of the first antigen-binding domain;   the carboxy-terminus of the heavy chain of the first antigen-binding domain; and/or   the carboxy-terminus of the light chain of the first antigen-binding domain.       

     In some embodiments, a bispecific binding molecule of the present disclosure is configured as shown in any of schematics A-E in  FIG. 1 . 
     In certain embodiments, the peptide linker conjugating the first and second antigen-binding domains is between 5-30, 5-25, 5-15, 10-30, 10-20, or 10-15 amino acids in length. In certain embodiments, the peptide linker comprises amino acids that allow for peptide linker solubility, such as, for example, serine and threonine. In certain embodiments, the linker may be charged (see, e.g., U.S. Pat. No. 9,856,327). In certain embodiments, the peptide linker comprises amino acids that allow for peptide linker flexibility, such as, for example, glycine, or for peptide linker rigidity. In certain embodiments, the sequence of the peptide linker conjugating the first and second antigen-binding domains is (Gly4-Ser)X, wherein X may be 1, 2, 3, or 4 (SEQ ID NO: 114). In particular embodiments, the sequence of the peptide linker is GGGGSGGGGS (SEQ ID NO: 93). 
     In some embodiments, a second antigen-binding domain as described herein comprises one or more mutations (e.g., replacement of amino acid residues with cysteines) to stabilize disulfide binding, e.g., to prevent or reduce aggregation of the bispecific binding molecule. 
     In some embodiments, a bispecific binding molecule of the present disclosure has a K D  for immobilized ROR1 of 100 nM, 50 nM, 40 nM, 30 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.9 nM, 0.8 nM, 0.7 nM, 0.6 nM, 0.5 nM, 0.4 nM, 0.3 nM, 0.2 nM, 0.1 nM, 0.09 nM, 0.08 nM, 0.07 nM, 0.06 nM, 0.05 nM, 0.04 nM, 0.03 nM, 0.02 nM, 0.01 nM, 0.005 nM, or 0.001 nM or less (e.g., 0.5 nM or less) as determined by ELISA. 
     In some embodiments, a bispecific binding molecule of the present disclosure has a K D  for soluble b-ROR1 of 100 nM, 50 nM, 40 nM, 30 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.9 nM, 0.8 nM, 0.7 nM, 0.6 nM, 0.5 nM, 0.4 nM, 0.3 nM, 0.2 nM, 0.1 nM, 0.09 nM, 0.08 nM, 0.07 nM, 0.06 nM, 0.05 nM, 0.04 nM, 0.03 nM, 0.02 nM, 0.01 nM, 0.005 nM, or 0.001 nM or less (e.g., 0.4 nM or less) as determined by ELISA. 
     In some embodiments, a bispecific binding molecule of the present disclosure has a K D  for CD3 of 100 nM, 50 nM, 40 nM, 30 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.9 nM, 0.8 nM, 0.7 nM, 0.6 nM, 0.5 nM, 0.4 nM, 0.3 nM, 0.2 nM, 0.1 nM, 0.09 nM, 0.08 nM, 0.07 nM, 0.06 nM, 0.05 nM, 0.04 nM, 0.03 nM, 0.02 nM, 0.01 nM, 0.005 nM, or 0.001 nM or less (e.g., 5 nM or less) as determined by ELISA. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces LDH release in PBMC-exposed ROR1-transfected MEC cells at 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces LDH release in PBMC-exposed JeKo-1 cells at 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces LDH release in PBMC-exposed Mino cells at 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, or 0.05 ng/mL, 0.01 ng/mL or less. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces LDH release in PBMC-exposed MDA-MB-468 cells at 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces ROR1-dependent killing of ROR1-transfected MEC cells, JeKo-1 cells, Mino cells, MDA-MB-468 cells, or any combination thereof, by PBMCs in vitro. 
     In some embodiments, a bispecific binding molecule of the present disclosure upregulates CD69 on the surface of T cells incubated with ROR1-transfected MEC cells at 50 μg/mL, 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less as determined by flow cytometry. 
     In some embodiments, a bispecific binding molecule of the present disclosure upregulates CD69 on the surface of T cells incubated with JeKo-1 cells at 50 μg/mL, 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less as determined by flow cytometry. 
     In some embodiments, a bispecific binding molecule of the present disclosure upregulates CD69 on the surface of T cells incubated with Mino cells at 50 μg/mL, 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less as determined by flow cytometry. 
     In some embodiments, a bispecific binding molecule of the present disclosure upregulates CD69 on the surface of T cells incubated with MDA-MB-468 cells at 50 μg/mL, 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less as determined by flow cytometry. 
     In some embodiments, a bispecific binding molecule of the present disclosure induces release of IFN-γ, TNF-α, IL-10, IL-6, IL-4, and IL-2 from T cells co-cultured with JeKo-1 or ROR1-transfected MEC cells at 10 μg/mL, 5 μg/mL, 1 μg/mL, 100 ng/mL, 50 ng/mL, 20 ng/mL, 10 ng/mL, 9 ng/mL, 8 ng/mL, 7 ng/mL, 6 ng/mL, 5 ng/mL, 4 ng/mL, 3 ng/mL, 2 ng/mL, 1 ng/mL, 0.9 ng/mL, 0.8 ng/mL, 0.7 ng/mL, 0.6 ng/mL, 0.5 ng/mL, 0.4 ng/mL, 0.3 ng/mL, 0.2 ng/mL, 0.1 ng/mL, 0.05 ng/mL, or 0.01 ng/mL or less. 
     In some embodiments, a bispecific binding molecule of the present disclosure has at least one of the following properties: 
     a) has a K D  for immobilized ROR1 of 0.5 nM or less as determined by ELISA;
 
b) has a K D  for soluble b-ROR1 of 0.4 nM or less as determined by ELISA;
 
c) demonstrates reduced internalization in ROR1-transfected MEC cells and/or Jurkat cells as compared to an antibody comprising the heavy and light chain amino acid sequences of SEQ ID NOs: 82 and 83, respectively;
 
d) induces LDH release in PBMC-exposed ROR1-transfected MEC cells at 1 μg/mL or less;
 
e) induces LDH release in PBMC-exposed JeKo-1 cells at 1 μg/mL or less;
 
f) induces LDH release in PBMC-exposed Mino cells at 1 μg/mL or less;
 
g) induces LDH release in PBMC-exposed MDA-MB-468 cells at 1 μg/mL or less;
 
h) upregulates CD69 on the surface of T cells co-cultured with ROR1-transfected MEC cells at 1 μg/mL or less as determined by flow cytometry;
 
i) upregulates CD69 on the surface of T cells co-cultured with JeKo-1 cells at 1 μg/mL or less as determined by flow cytometry;
 
j) upregulates CD69 on the surface of T cells co-cultured with Mino cells at 1 μg/mL or less as determined by flow cytometry;
 
k) upregulates CD69 on the surface of T cells co-cultured with MDA-MB-468 cells at 1 μg/mL or less as determined by flow cytometry; and
 
l) induces release of IFN-γ, TNF-α, IL-10, IL-6, IL-4, and IL-2 from T cells co-cultured with JeKo-1 or ROR1-transfected MEC cells at 1 μg/mL or less.
 
In certain embodiments, a bispecific binding molecule of the present disclosure has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 of said properties. In particular embodiments, a bispecific binding molecule of the present disclosure has all of said properties.
 
     In some embodiments, a bispecific binding molecule of the present disclosure induces T cell cytotoxicity against ROR1-positive cells. 
     Nucleic Acid Molecules and Vectors 
     The present disclosure also provides nucleic acid molecules and sequences encoding bispecific binding molecules described herein. In some embodiments, different nucleic acid molecules encode different polypeptides that form the bispecific binding molecule. In other embodiments, the same nucleic acid molecule encodes more than one, or all, of the polypeptides that form the bispecific binding molecule. 
     A reference to a nucleotide sequence encompasses its complement unless otherwise specified. Thus, a reference to a nucleic acid having a particular sequence should be understood to encompass its complementary strand, with its complementary sequence. The term “polynucleotide” as referred to herein means a polymeric form of nucleotides of at least 10 bases in length, either ribonucleotides or deoxynucleotides or a modified form of either type of nucleotide. The term includes single- and double-stranded forms. 
     In any of the above embodiments, the nucleic acid molecules may be isolated. Nucleic acid molecules referred to herein as “isolated” or “purified” are nucleic acids which (1) have been separated away from the nucleic acids of the genomic DNA or cellular RNA of their source of origin; and/or (2) do not occur in nature. 
     In some embodiments, a nucleic acid molecule of the present disclosure comprises nucleotide sequences that encode:
         H-CDR1-3 and/or L-CDR1-3 of the first antigen-binding domain   H-CDR1-3 and/or L-CDR1-3 of the second antigen-binding domain;   VH and/or VL of the first antigen-binding domain;   VH and/or VL of the second antigen-binding domain; and/or   HC and/or LC of the first antigen-binding domain;
 
of a bispecific binding molecule of the present disclosure.
       

     In some embodiments, a nucleic acid molecule of the present disclosure comprises nucleotide sequences that encode H-CDR1-3 and L-CDR1-3 of the first antigen-binding domain, and further comprises nucleotide sequences that encode H-CDR1-3 and L-CDR1-3 of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. In some embodiments, a nucleic acid molecule of the present disclosure comprises nucleotide sequences that encode the VH and VL of the first antigen-binding domain, and further comprises nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. In some embodiments, a nucleic acid molecule of the present disclosure comprises nucleotide sequences that encode the HC and LC of the first antigen-binding domain, and further comprises nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. 
     In some embodiments, a nucleic acid molecule of the present disclosure comprises one or more nucleotide sequences selected from the group consisting of SEQ ID NOs: 24-46. 
     In certain embodiments, a nucleic acid molecule of the present disclosure comprises:
         the nucleotide sequences of SEQ ID NOs: 24 and 39;   the nucleotide sequences of SEQ ID NOs: 25 and 39;   the nucleotide sequences of SEQ ID NOs: 26 and 39;   the nucleotide sequences of SEQ ID NOs: 27 and 39;   the nucleotide sequences of SEQ ID NOs: 28 and 39;   the nucleotide sequences of SEQ ID NOs: 29 and 39;   the nucleotide sequences of SEQ ID NOs: 30 and 40;   the nucleotide sequences of SEQ ID NOs: 30 and 41;   the nucleotide sequences of SEQ ID NOs: 30 and 42;   the nucleotide sequences of SEQ ID NOs: 30 and 43;   the nucleotide sequences of SEQ ID NOs: 30 and 44;   the nucleotide sequences of SEQ ID NOs: 30 and 45;   the nucleotide sequences of SEQ ID NOs: 31, 32, and 39;   the nucleotide sequences of SEQ ID NOs: 31, 33 and 39;   the nucleotide sequences of SEQ ID NOs: 31, 34, and 39;   the nucleotide sequences of SEQ ID NOs: 35, 34, and 39;   the nucleotide sequences of SEQ ID NOs: 35, 36, and 39;   the nucleotide sequences of SEQ ID NOs: 37 and 42;   the nucleotide sequences of SEQ ID NOs: 31, 38, and 39; or   the nucleotide sequences of SEQ ID NOs: 30 and 46.       

     In a further aspect, the present disclosure provides a vector suitable for expressing one or more of the polypeptides that form a bispecific binding molecule as described herein. The term “vector”, as used herein, means a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. In some embodiments, the vector is a plasmid, i.e., a circular double stranded piece of DNA into which additional DNA segments may be ligated. In some embodiments, the vector is a viral vector, wherein additional DNA segments may be ligated into the viral genome. In some embodiments, the vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). In other embodiments, the vectors (e.g., non-episomal mammalian vectors) can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as “recombinant expression vectors” (or simply, “expression vectors”). 
     In some embodiments, a nucleic acid molecule of the present disclosure can comprise a nucleotide sequence encoding an amino acid sequence from the first antigen-binding domain joined in-frame to a nucleotide sequence encoding an amino acid sequence from the second antigen-binding domain. 
     In some embodiments, the bispecific binding molecules of the present disclosure are expressed by inserting DNAs encoding polypeptide components of the bispecific binding molecules into expression vectors such that the DNAs are operatively linked to necessary expression control sequences such as transcriptional and translational control sequences. Expression vectors include plasmids, retroviruses, adenoviruses, adeno-associated viruses (AAVs), plant viruses such as cauliflower mosaic virus, tobacco mosaic virus, cosmids, YACs, EBV derived episomes, and the like. The coding sequence may be ligated into a vector such that transcriptional and translational control sequences within the vector serve their intended function of regulating the transcription and translation of the coding sequence. The expression vector and expression control sequences may be chosen to be compatible with the expression host cell used. Nucleotide sequences that encode different polypeptide components of a bispecific binding molecule of the present disclosure may be inserted into the same or separate vectors, and may be operatively linked to the same or different expression control sequences (e.g., promoters). In one embodiment, two or more coding sequences are inserted into the same expression vector and may be operatively linked to the same expression control sequences (e.g., a common promoter), to separate identical expression control sequences (e.g., promoters), or to different expression control sequences (e.g., promoters). The coding sequences may be inserted into the expression vector by standard methods (e.g., ligation of complementary restriction sites on the antibody gene fragment and vector, or blunt end ligation if no restriction sites are present). 
     Host Cells and Methods of Bispecific Binding Molecule Production 
     An additional aspect of the present disclosure relates to methods for producing the bispecific binding molecules of the present disclosure. In some embodiments, a method for producing a bispecific binding molecule as defined herein comprises providing a recombinant host cell capable of expressing the bispecific binding molecule (e.g., a host cell as described herein), cultivating said host cell under conditions suitable for expression of the bispecific binding molecule, and isolating the resulting bispecific binding molecule. 
     Mammalian cell lines available as hosts for expression are well known in the art and include many immortalized cell lines available from the American Type Culture Collection (ATCC). These include, inter alia, Chinese hamster ovary (CHO) cells, NS0 cells, SP2 cells, HEK-293T cells, 293 Freestyle cells (Invitrogen), NIH-3T3 cells, HeLa cells, baby hamster kidney (BHK) cells, African green monkey kidney cells (COS), human hepatocellular carcinoma cells (e.g., Hep G2), A549 cells, and a number of other cell lines. Other cell lines that may be used are insect cell lines, such as Sf9 or Sf21 cells, and yeast cell lines. Cell lines may be selected based on their expression levels. 
     In some embodiments, a host cell of the present disclosure comprises nucleotide sequences that encode:
         H-CDR1-3 and/or L-CDR1-3 of the first antigen-binding domain   H-CDR1-3 and/or L-CDR1-3 of the second antigen-binding domain;   VH and/or VL of the first antigen-binding domain;   VH and/or VL of the second antigen-binding domain; and/or   HC and/or LC of the first antigen-binding domain;
 
of a bispecific binding molecule of the present disclosure.
       

     In some embodiments, a host cell of the present disclosure comprises nucleotide sequences that encode H-CDR1-3 and L-CDR1-3 of the first antigen-binding domain, and further comprises nucleotide sequences that encode H-CDR1-3 and L-CDR1-3 of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. In some embodiments, a host cell of the present disclosure comprises nucleotide sequences that encode the VH and VL of the first antigen-binding domain, and further comprises nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. In some embodiments, a host cell of the present disclosure comprises nucleotide sequences that encode the HC and LC of the first antigen-binding domain, and further comprises nucleotide sequences that encode the VH and VL of the second antigen-binding domain, of a bispecific binding molecule of the present disclosure. 
     In some embodiments, a host cell of the present disclosure comprises one or more nucleotide sequences selected from the group consisting of SEQ ID NOs: 24-46. 
     In certain embodiments, a host cell of the present disclosure comprises:
         the nucleotide sequences of SEQ ID NOs: 24 and 39;   the nucleotide sequences of SEQ ID NOs: 25 and 39;   the nucleotide sequences of SEQ ID NOs: 26 and 39;   the nucleotide sequences of SEQ ID NOs: 27 and 39;   the nucleotide sequences of SEQ ID NOs: 28 and 39;   the nucleotide sequences of SEQ ID NOs: 29 and 39;   the nucleotide sequences of SEQ ID NOs: 30 and 40;   the nucleotide sequences of SEQ ID NOs: 30 and 41;   the nucleotide sequences of SEQ ID NOs: 30 and 42;   the nucleotide sequences of SEQ ID NOs: 30 and 43;   the nucleotide sequences of SEQ ID NOs: 30 and 44;   the nucleotide sequences of SEQ ID NOs: 30 and 45;   the nucleotide sequences of SEQ ID NOs: 31, 32, and 39;   the nucleotide sequences of SEQ ID NOs: 31, 33 and 39;   the nucleotide sequences of SEQ ID NOs: 31, 34, and 39;   the nucleotide sequences of SEQ ID NOs: 35, 34, and 39;   the nucleotide sequences of SEQ ID NOs: 35, 36, and 39;   the nucleotide sequences of SEQ ID NOs: 37 and 42;   the nucleotide sequences of SEQ ID NOs: 31, 38, and 39; or   the nucleotide sequences of SEQ ID NOs: 30 and 46.       

     Pharmaceutical Compositions 
     Another aspect of the present disclosure is a pharmaceutical composition comprising as an active ingredient (or as the sole active ingredient) a bispecific binding molecule of the present disclosure. The pharmaceutical composition may comprise any bispecific binding molecule as described herein. In some embodiments, the compositions are intended for amelioration, prevention, and/or treatment of cancer described herein (e.g., a ROR1-positive cancer). 
     Generally, a bispecific binding molecule of the present disclosure is suitable to be administered as a formulation in association with one or more pharmaceutically acceptable excipient(s), e.g., as described below. 
     The term “excipient” is used herein to describe any ingredient other than the compound(s) of the present disclosure. The choice of excipient(s) will to a large extent depend on factors such as the particular mode of administration, the effect of the excipient on solubility and stability, and the nature of the dosage form. As used herein, “pharmaceutically acceptable excipient” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. Some examples of pharmaceutically acceptable excipients are water, saline, phosphate buffered saline, dextrose, glycerol, ethanol and the like, as well as combinations thereof. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, or sodium chloride in the composition. Additional examples of pharmaceutically acceptable substances are wetting agents or minor amounts of auxiliary substances such as wetting or emulsifying agents, preservatives or buffers, which enhance the shelf life or effectiveness of the bispecific binding molecule. 
     Pharmaceutical compositions of the present disclosure and methods for their preparation will be readily apparent to those skilled in the art. Such compositions and methods for their preparation may be found, for example, in Remington&#39;s Pharmaceutical Sciences, 19th Edition (Mack Publishing Company, 1995). Pharmaceutical compositions are preferably manufactured under GMP (good manufacturing practices) conditions. 
     A pharmaceutical composition of the present disclosure may be prepared, packaged, or sold in bulk, as a single unit dose, or as a plurality of single unit doses. As used herein, a “unit dose” is a discrete amount of the pharmaceutical composition comprising a predetermined amount of the active ingredient. The amount of the active ingredient is generally equal to the dosage of the active ingredient which would be administered to a subject or a convenient fraction of such a dosage such as, for example, one-half or one-third of such a dosage. 
     Any method for administering peptides, proteins or antibodies accepted in the art may suitably be employed for the bispecific binding molecules of the present disclosure. 
     The pharmaceutical compositions of the present disclosure are typically suitable for parenteral administration. As used herein, “parenteral administration” of a pharmaceutical composition includes any route of administration characterized by physical breaching of a tissue of a subject and administration of the pharmaceutical composition through the breach in the tissue, thus generally resulting in the direct administration into the blood stream, into muscle, or into an internal organ. Parenteral administration thus includes, but is not limited to, administration of a pharmaceutical composition by injection of the composition, by application of the composition through a surgical incision, by application of the composition through a tissue-penetrating non-surgical wound, and the like. In particular, parenteral administration is contemplated to include, but is not limited to, subcutaneous, intraperitoneal, intramuscular, intrasternal, intravenous, intraarterial, intrathecal, intraventricular, intraurethral, intracranial, intratumoral, and intrasynovial injection or infusions; and kidney dialytic infusion techniques. Regional perfusion is also contemplated. Particular embodiments include the intravenous and the subcutaneous routes. 
     Formulations of a pharmaceutical composition suitable for parenteral administration (e.g., intravenous administration) typically comprise the active ingredient combined with a pharmaceutically acceptable carrier, such as sterile water or sterile isotonic saline. Such formulations may be prepared, packaged, or sold in a form suitable for bolus administration or for continuous administration. Injectable formulations may be prepared, packaged, or sold in unit dosage form, such as in ampoules or in multi-dose containers containing a preservative. Formulations for parenteral administration include, but are not limited to, suspensions, solutions, emulsions in oily or aqueous vehicles, pastes, and the like. Such formulations may further comprise one or more additional ingredients including, but not limited to, suspending, stabilizing, or dispersing agents. In one embodiment of a formulation for parenteral administration, the active ingredient is provided in dry (i.e., powder or granular) form for reconstitution with a suitable vehicle (e.g., sterile pyrogen-free water) prior to parenteral administration of the reconstituted composition. Parenteral formulations also include aqueous solutions which may contain excipients such as salts, carbohydrates and buffering agents (preferably to a pH of from 3 to 9), but, for some applications, they may be more suitably formulated as a sterile non-aqueous solution or as a dried form to be used in conjunction with a suitable vehicle such as sterile, pyrogen-free water. Exemplary parenteral administration forms include solutions or suspensions in sterile aqueous solutions, for example, aqueous propylene glycol or dextrose solutions. Such dosage forms can be suitably buffered, if desired. Other parentally-administrable formulations which are useful include those which comprise the active ingredient in microcrystalline form, or in a liposomal preparation. Formulations for parenteral administration may be formulated to be immediate and/or modified release. Modified release formulations include delayed-, sustained-, pulsed-, controlled-, targeted and programmed release. Therapeutic Uses of Bispecifc Binding Molecules 
     In some embodiments, a bispecific binding molecule of the present disclosure is used to treat cancer, such as a ROR1-positive cancer, in a patient. The patient may be a mammal, e.g., a human. ROR1 has been shown to express across many types of tumors, including lymphomas and solid tumors. High proportions of human cancers express ROR1. For example, Zhang et al. showed that 54% of ovarian cancers, 57% of colon cancers, 77% of lung cancers, 90% of lymphomas, 89% of skin cancers, 83% of pancreatic cancers, 73% of testicular cancers, 43% of bladder cancers, 96% of uterus cancers, 90% of prostate cancers, and 83% of adrenal cancers that they examined had moderate-to-strong staining with the anti-ROR1 antibody 4A5 (Zhang et al.,  Am J Pathol.  181(6):1903-10 (2012)). Daneshmanesh et al. similarly found near universal expression of ROR1 in chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) and varying degrees of expression in other lymphoid cancers such as mantle cell lymphoma (MCL), diffuse large B-cell lymphoma (DLBCL)/marginal zone lymphoma (MZL), follicular lymphoma (FL), chronic myeloid leukemia (CML), acute myeloid leukemia (AML), and myeloma (Daneshmanesh et al.,  Leuk Lymphoma  54(4):843-50 (2013)). Multiple groups have demonstrated expression of ROR1 in a subset of B-cell acute lymphoblastic leukemia (ALL) (see, e.g., Dave et al.,  PLoS One  7:e52655 (2012)). ROR1 is also expressed in substantial proportions of cases of hepatocellular cancer (HCC) or non-small cell lung cancer (NSCLC) (U.S. Patent Publication 2018/0369406). Further, it has been shown that ROR1 expression increases in aggressive cancers and correlates with poor prognosis; thus, bispecific binding molecules of the present disclosure are particularly well suited to treat aggressive or advanced cancers. 
     “Treat”, “treating” and “treatment” refer to a method of alleviating or abrogating a biological disorder and/or at least one of its attendant symptoms. As used herein, to “alleviate” a disease, disorder or condition means reducing the severity and/or occurrence frequency of the symptoms of the disease, disorder, or condition. Further, references herein to “treatment” include references to curative, palliative and prophylactic treatment. Treatment of cancer encompasses inhibiting cancer growth (including causing partial or complete cancer regression), inhibiting cancer progression or metastasis, preventing cancer recurrence or residual disease, and/or prolonging the patient&#39;s survival. 
     A bispecific binding molecule may be administered in a therapeutically effective amount to a patient with a cancer described herein. “Therapeutically effective amount” refers to the amount of the therapeutic agent being administered that will relieve to some extent one or more of the symptoms of the disorder being treated. A therapeutically effective amount of an anti-cancer therapeutic may, for example, result in tumor shrinkage, increased survival, elimination of cancer cells, decreased disease progression, reversal of metastasis, or other clinical endpoints desired by healthcare professionals. 
     In some embodiments, a cancer treatable by a bispecific binding molecule described herein is a ROR1-expressing (i.e., ROR1-positive) cancer. The cancer can be identified as ROR1-expressing by any suitable method of determining gene or protein expression, for example, by histology, flow cytometry, RT-PCR, or RNA-Seq. The cancer cells used for the determination may be obtained through tumor biopsy or through collection of circulating tumor cells. In certain embodiments, if an antibody-based assay such as flow cytometry or immunohistochemistry is used, ROR1-expressing cancers are any cancers with cells that show anti-ROR1 antibody reactivity greater than that of an isotype control antibody. In certain embodiments, if an RNA-based assay is used, ROR1-expressing cancers are those that show an elevated level of ROR1 RNA compared to a negative control cell or cancer that does not express ROR1. 
     In certain embodiments, bispecific binding molecules of the present disclosure are used to treat hematological malignancies (e.g., leukemias and/or lymphomas). In certain embodiments, bispecific binding molecules of the present disclosure are used to treat solid tumors. The cancer to be treated may be selected from, e.g., lymphoma, small lymphocytic lymphoma, marginal zone lymphoma, marginal cell B-cell lymphoma, Burkitt&#39;s lymphoma, mantle cell lymphoma, follicular lymphoma, diffuse large B-cell lymphoma, a non-Hodgkin lymphoma that has undergone Richter&#39;s transformation, T cell non-Hodgkin lymphoma, lymphoplasmacytoid lymphoma, Waldenström macroglobulinemia, acute lymphoblastic leukemia, acute myeloid leukemia, chronic lymphocytic leukemia, T cell leukemia, sarcoma, osteosarcoma, Ewing sarcoma, renal cell carcinoma, hepatocellular carcinoma, colon cancer, colorectal cancer, breast cancer, epithelial squamous cell cancer, glioblastoma, melanoma, myeloma, multiple myeloma, stomach cancer, brain cancer, lung cancer, non-small cell lung cancer, pancreatic cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, prostate cancer, testicular cancer, thyroid cancer, and head and neck cancer. In certain embodiments, the cancer is selected from mantle cell lymphoma, breast cancer, lung cancer, bone osteosarcoma, and Ewing sarcoma. 
     In some embodiments, the cancer to be treated can be a cancer that is refractory to other therapeutics (for example, triple negative breast cancer). The cancer may be, e.g., at an early, intermediate, late, or metastatic stage. 
     In some embodiments, a patient to be treated with a bispecific binding molecule of the present disclosure has received prior cancer treatment. In other aspects, the patient has not received prior cancer treatment. 
     A bispecific binding molecule of the present disclosure may be administered without additional therapeutic treatments, i.e., as a stand-alone therapy (monotherapy). Alternatively, treatment with a bispecific binding molecule of the present disclosure may include at least one additional therapeutic treatment (combination therapy). In some embodiments, a bispecific binding molecule may be co-administered or formulated with another medication/drug for the treatment of cancer. The additional treatment may comprise, e.g., a chemotherapeutic, anti-neoplastic, or anti-angiogenic agent, a different anti-cancer antibody, and/or radiation therapy. 
     In certain embodiments, a bispecific binding molecule of the present disclosure is used in combination with an additional therapeutic agent or biologically active molecule (e.g., to treat a cancer described herein). Examples of biologically active molecules include, but are not limited to, peptides, proteins, enzymes, small molecule drugs, prodrugs, carbohydrates, imaging agents, lipids, nucleosides, radionuclides, oligonucleotides, toxins, cells, antibiotics, fungicides, anti-viral agents, anti-inflammatory agents, anti-tumor agents, cardiovascular agents, anti-anxiety agents, hormones, growth factors, steroidal agents, microbially derived toxins, and the like. In some embodiments, the additional therapeutic agent is a vascular endothelial growth factor (VEGF) inhibitor, a Bruton&#39;s tyrosine kinase (BTK) inhibitor, an inhibitor of the mammalian target of rapamycin (mTOR), a phosphoinositide 3-kinase (PI3K) inhibitor, a Janus kinase/signal transducers and activators of transcription (Jak/STAT) signaling inhibitor, a B-cell lymphoma 2 (Bcl-2) inhibitor, a spleen tyrosine kinase (SYK) inhibitor, a microtubule inhibitor, an epithelial growth factor receptor (EGFR) inhibitor, a poly ADP ribose polymerase (PARP) inhibitor, an anaplastic lymphoma kinase (ALK) inhibitor, a DNA-repair inhibitor, a DNA cross-linker, a nucleoside analog, or an immunomodulatory agent. In some embodiments, the additional therapeutic agent is an antibody such as rituximab (anti-CD20) or bevacizumab (anti-VEGF); a Bruton&#39;s tyrosine kinase inhibitor such as acalabrutinib or ibrutinib; an mTOR inhibitor such as sapanisertib, everolimus or BEZ235; a PI3K inhibitor such as idelalisib or buparlisib; a Jak/STAT signaling inhibitor such as ruxolitinib; a Bcl-2 inhibitor such as ABT-199/venetoclax, Bcl-2i-1, or Bcl-2i-2; a SYK inhibitor such as fostamatinib; a microtubule inhibitor such as paclitaxel or vincristine; an EGFR inhibitor such as erlotinib; a PARP inhibitor such as olaparib; an ALK inhibitor such as crizotinib; a DNA-repair inhibitor such as carboplatin; a DNA cross-linker such as oxaliplatin/cisplatin; a nucleoside analog such as gemcitabine; or an immunomodulatory drug (IMiD) such as lenalidomide or pomalidomide. In certain embodiments, the additional therapeutic agent is ibrutinib, acalabrutinib, venetoclax, Bcl-2i-1, Bcl-2i-2, everolimus, sapanisertib, idelalisib, pacritinib, buparlisib, BEZ235, ruxolitinib, fostamatinib, rituximab, rituximab-CHOP, lenalidomide, pomalidomide, paclitaxel, vincristine, erlotinib, crizotinib, carboplatin, oxaliplatin/cisplatin, bevacizumab, or gemcitabine. 
     In certain embodiments, a bispecific binding molecule of the invention is used in combination with an immune checkpoint modulator that enhances the patient&#39;s immune system (e.g., to treat a cancer as described herein). For example, the conjugate is used with an immune checkpoint inhibitor such as an antibody or antibody derivative, an antisense oligonucleotide, a small interfering RNA, an aptamer, or a peptide, targeting programmed death-ligand 1 (PD-L1, also known as B7-H1, CD274), programmed death 1 (PD-1), CTLA-4, PD-L2 (B7-DC, CD273), LAG3, TIM3, 2B4, A2aR, B7H1, B7H3, B7H4, BTLA, CD2, CD27, CD28, CD30, CD40, CD70, CD80, CD86, CD137, CD160, CD226, CD276, DR3, GAL9, GITR, HAVCR2, HVEM, IDO1, IDO2, ICOS (inducible T cell costimulator), KIR, LAIR1, LIGHT, MARCO (macrophage receptor with collagenous structure), PS (phosphatidylserine), OX-40, SLAM, TIGHT, VISTA, VTCN1, or any combination thereof. 
     In certain embodiments, a bispecific binding molecule of the present disclosure is administered to a patient in combination with T cells (e.g., T cells autologous or allogeneic to the patient). In particular embodiments, where the patient is human, the T cells are also human. In some embodiments, the bispecific binding molecule is bound to the T cells before administration to the patient. 
     It is understood that bispecific binding molecules of the present disclosure may be used in a method of treatment as described herein, may be for use in a treatment as described herein, and/or may be used in the manufacture of a medicament for a treatment as described herein. The present disclosure also provides kits and articles of manufacture comprising bispecific binding molecules of the present disclosure as described herein. 
     Articles of Manufacture and Kits 
     The present disclosure also provides articles of manufacture, e.g., kits, comprising one or more containers (e.g., single-use or multi-use containers) containing a pharmaceutical composition of the bispecific binding molecule of the present disclosure, optionally an additional biologically active molecule (e.g., another therapeutic agent), and instructions for use. The bispecific binding molecule and optional additional biologically active molecule can be packaged separately in suitable packing such as a vial or ampule made from non-reactive glass or plastic. In certain embodiments, the vial or ampule holds lyophilized powder comprising the bispecific binding molecule and/or additional biologically active molecule. In certain embodiments, the vial or ampule holds a concentrated stock (e.g., 2×, 5×, 10× or more) of the bispecific binding molecule or biologically active molecule. In certain embodiments, the articles of manufacture such as kits include a medical device for administering the bispecific binding molecule and/or biologically active molecule (e.g., a syringe and a needle); and/or an appropriate diluent (e.g., sterile water and normal saline). The present disclosure also includes methods for manufacturing said articles. 
     Unless otherwise defined herein, scientific and technical terms used in connection with the present disclosure shall have the meanings that are commonly understood by those of ordinary skill in the art. Exemplary methods and materials are described below, although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure. In case of conflict, the present specification, including definitions, will control. 
     Generally, nomenclature used in connection with, and techniques of, cell and tissue culture, molecular biology, immunology, microbiology, genetics, analytical chemistry, synthetic organic chemistry, medicinal and pharmaceutical chemistry, and protein and nucleic acid chemistry and hybridization described herein are those well-known and commonly used in the art. Enzymatic reactions and purification techniques are performed according to manufacturer&#39;s specifications, as commonly accomplished in the art or as described herein. 
     Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. Throughout this specification and embodiments, the words “have” and “comprise,” or variations such as “has,” “having,” “comprises,” or “comprising,” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 
     All publications and other references mentioned herein are incorporated by reference in their entirety. Although a number of documents are cited herein, this citation does not constitute an admission that any of these documents forms part of the common general knowledge in the art. 
     In order that this invention may be better understood, the following examples are set forth. These examples are for purposes of illustration only and are not to be construed as limiting the scope of the invention in any manner. 
     EXAMPLES 
     The following examples illustrate representative embodiments of the present invention and are not meant to be limiting in any way. 
     Example 1: Design and Expression of Anti-ROR1/Anti-CD3 Bispecific Binding Molecules 
     Multiple variables impact the in vivo potency of bispecific binding molecules, including PK, epitopes, the relative affinities of the binding components, and the valency and spatial configuration of the paratopes. Currently, there is no reliable method for designing apriori a single molecule that optimizes all these parameters. Accordingly, multiple anti-ROR1/anti-CD3 bispecific constructs were designed, made, and tested to systematically evaluate the impact of many of these parameters. 
     To identify the structure that provides the optimal configuration, specifically the most active relative spatial placement of the ROR1 and CD3 binding components, a variety of constructs were designed as summarized in  FIG. 1 . Although a variety of bispecific formats have been described (see, e.g., Brinkmann and Kontermann,  MABS  9:182-212 (2017)), the present efforts focused on formats that contain antibody Fc component in order to enable favorable PK and use well-established Protein A-based antibody purification approaches. 
     The ROR1 binding component used in the bispecific binding molecules has been demonstrated to be highly selective for human ROR1 and has proven to be safe in human clinical trials (see, e.g., Choi et al.,  Cell Stem Cell  22:951-959 (2018)). Further, bispecific binding molecules were tested with CD3 binding components specific for two distinct CD3 epitopes, using anti-CD3 scFv sequences based on the SP34 and OKT3 antibodies. CD3 antibodies have been classified based on distinct characteristics of their epitopes (Tunnacliffe et al.,  International Immunology  1:546-550 (1989)). Using this system, SP34 is classified as Group I while OKT3 is classified as Group II. 
     For certain constructs, use of wild-type antibody Fc sequences enabled the evaluation of bispecific constructs that are bivalent for both ROR1 and CD3 ( FIGS. 1 , A, B, and E). For other constructs, the use of knobs-into-holes mutations in the Fc region enabled the expression of bispecific binding molecules with different valencies for ROR1 and CD3. For example, one construct is bivalent for ROR1 and monovalent for CD3 ( FIG. 1 , D) while another construct is monovalent for both ROR1 and CD3 ( FIG. 1 , C). 
     Finally, ROR1 paratopes with altered affinities and valencies were tested in combination with the different CD3 paratopes to evaluate the effect of CD3 and ROR1 paratopes with differing relative affinities/avidities. 
     Based on these design parameters, multiple bispecific constructs were expressed, purified and characterized. 
     Materials and Methods 
     Codon-optimized DNA encoding the bispecific constructs with a leader sequence of SEQ ID NO: 110 was cloned into the pcDNA3.4 vector, then introduced into Expi293 cells by transient transfection. The cells were grown in 40 mL cultures containing Expi293F Expression Medium (ThermoFisher cat. #A1435103). Subsequently, antibody was purified from the culture supernatant in a single step using HiTrap MabSelect SuRe (GE Healthcare cat. #11-0034-93). Purified antibody was stored in PBS, pH 7.2, and purity was characterized by SDS-PAGE. The purity of constructs consisting of three distinct polypeptide chains was further characterized by SEC using a TSKgel G3000SWxl 7.8 mm×380 mm column. The mobile phase was 0.1M phosphate buffer, 0.1M Na 2 SO 4 , pH 6.7, and the column was run at a flow rate of 0.7 mL/min. 
     Results 
     The sequences of the anti-ROR1/anti-CD3 bispecific binding molecules are summarized in Table 1 (protein) and Table 2 (DNA). 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Summary of Bispecific Construct Polypeptide Sequences 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Polypeptide 1 
                 Polypeptide 2 
                 Polypeptide 3 
                   
                   
                   
               
               
                   
                 (Heavy Chain 1) 
                 (Heavy Chain 2) 
                 (Light Chain)  
                 CD3 
                 ROR1 
                 Schematic 
               
               
                 Construct 
                 SEQ ID 
                 SEQ ID 
                 SEQ ID 
                 Valency 
                 Valency 
                 (FIG. 1) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 1 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 2 
                 2 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 3 
                 3 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 4 
                 4 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 5 
                 5 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 6 
                 6 
                   
                 16 
                 2 
                 2 
                 A 
               
               
                 7 
                 7 
                   
                 17 
                 2 
                 2 
                 B 
               
               
                 8 
                 7 
                   
                 18 
                 2 
                 2 
                 B 
               
               
                 9 
                 7 
                   
                 19 
                 2 
                 2 
                 B 
               
               
                 10 
                 7 
                   
                 20 
                 2 
                 2 
                 B 
               
               
                 11 
                 7 
                   
                 21 
                 2 
                 2 
                 B 
               
               
                 12 
                 7 
                   
                 22 
                 2 
                 2 
                 B 
               
               
                 13 
                 8 
                 9 
                 16 
                 1 
                 1 
                 C 
               
               
                 14 
                 8 
                 10 
                 16 
                 1 
                 1 
                 C 
               
               
                 15 
                 8 
                 11 
                 16 
                 1 
                 1 
                 C 
               
               
                 16 
                 12 
                 11 
                 16 
                 1 
                 1 
                 C 
               
               
                 17 
                 12 
                 13 
                 16 
                 1 
                 1 
                 C 
               
               
                 18 
                 14 
                   
                 19 
                 2 
                 2 
                 B 
               
               
                 19 
                 8 
                 15 
                 16 
                 1 
                 2 
                 D 
               
               
                 20 
                 7 
                   
                 23 
                 2 
                 2 
                 E 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Summary of Bispecific Construct DNA Sequences 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Heavy Chain 1 
                 Heavy Chain 2 
                 Light Chain 
                 CD3 
                 ROR1 
                 Schematic 
               
               
                 Construct 
                 SEQ ID 
                 SEQ ID 
                 SEQ ID 
                 Valency 
                 Valency 
                 (FIG. 1) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 24 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 2 
                 25 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 3 
                 26 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 4 
                 27 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 5 
                 28 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 6 
                 29 
                   
                 39 
                 2 
                 2 
                 A 
               
               
                 7 
                 30 
                   
                 40 
                 2 
                 2 
                 B 
               
               
                 8 
                 30 
                   
                 41 
                 2 
                 2 
                 B 
               
               
                 9 
                 30 
                   
                 42 
                 2 
                 2 
                 B 
               
               
                 10 
                 30 
                   
                 43 
                 2 
                 2 
                 B 
               
               
                 11 
                 30 
                   
                 44 
                 2 
                 2 
                 B 
               
               
                 12 
                 30 
                   
                 45 
                 2 
                 2 
                 B 
               
               
                 13 
                 31 
                 32 
                 39 
                 1 
                 1 
                 C 
               
               
                 14 
                 31 
                 33 
                 39 
                 1 
                 1 
                 C 
               
               
                 15 
                 31 
                 34 
                 39 
                 1 
                 1 
                 C 
               
               
                 16 
                 35 
                 34 
                 39 
                 1 
                 1 
                 C 
               
               
                 17 
                 35 
                 36 
                 39 
                 1 
                 1 
                 C 
               
               
                 18 
                 37 
                   
                 42 
                 2 
                 2 
                 B 
               
               
                 19 
                 31 
                 38 
                 39 
                 1 
                 2 
                 D 
               
               
                 20 
                 30 
                   
                 46 
                 2 
                 2 
                 E 
               
               
                   
               
            
           
         
       
     
     The majority of the constructs expressed well (17/20 expressed &gt;1 mg; 14/20 expressed &gt;2 mg) and in most cases were substantially purified in a single step using Protein A chromatography (Table 3), as determined by SDS-PAGE. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Summary of Expression and Purification of Bispecific Constructs 
               
            
           
           
               
               
               
               
            
               
                 Construct 
                 Yield (mg) 
                 Concentration (mg/mL) 
                 Purity (%) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 1 
                 2.72 
                 0.34 
                 90 
               
               
                 2 
                 5.32 
                 0.76 
                 95 
               
               
                 3 
                 1.36 
                 0.68 
                 95 
               
               
                 4 
                 3.52 
                 0.44 
                 60 
               
               
                 5 
                 5.49 
                 0.61 
                 55 
               
               
                 6 
                 0.38 
                 0.19 
                 90 
               
               
                 7 
                 7.84 
                 3.92 
                 95 
               
               
                 8 
                 5.50 
                 5.50 
                 95 
               
               
                 9 
                 1.93 
                 1.29 
                 95 
               
               
                 10 
                 3.28 
                 0.41 
                 65 
               
               
                 11 
                 3.78 
                 0.63 
                 70 
               
               
                 12 
                 0.19 
                 0.12 
                 65 
               
               
                 13 
                 8.47 
                 1.21 
                 73 
               
               
                 14 
                 9.08 
                 4.54 
                 95 
               
               
                 15 
                 9.20 
                 1.15 
                 65 
               
               
                 16 
                 7.42 
                 1.06 
                 80 
               
               
                 17 
                 4.60 
                 0.92 
                 79 
               
               
                 18 
                 0.89 
                 0.59 
                 90 
               
               
                 19 
                 4.60 
                 0.92 
                 60 
               
               
                 20 
                 1.32 
                 0.88 
                 85 
               
               
                   
               
            
           
         
       
     
     Constructs that did not contain disulfide-stabilized anti-CD3 scFv were generally of higher purity (&gt;90%) after Protein A chromatography (Table 3, compare constructs 2 and 5). 
     SEC analysis was performed on constructs consisting of three distinct polypeptide chains. In general, following a single Protein A purification step, constructs consisting of two distinct chains (wild-type Fc) were obtained in higher purity than constructs consisting of three distinct chains (heteromeric Fc) (Table 3, compare purity of samples 1-3 and 7-9 with samples 13-17). 
     Collectively, these data demonstrate that most of the constructs express well and are &gt;90% pure after a single Protein A purification step. 
     Example 2: Binding of Anti-ROR1/Anti-CD3 Bispecific Binding Molecules to ROR1 
     Bispecific binding molecules with different configurations, ROR1 affinities, and ROR1 valencies were evaluated for binding to human ROR1 to determine the impact of these parameters on cytotoxicity. The binding of bispecific constructs 1-20 to human ROR1 was characterized using ROR1-transfected MEC cells, JeKo-1 cells, and recombinant ROR1 extracellular domain (ECD). 
     Materials and Methods 
     ROR1 Binding Assay Using Cells and Flow Cytometry 
     ROR1 binding was quantitated using both ROR1-transfected MEC cells and JeKo-1 cells. For each condition, 2.5E5 cells were used. The cells were placed in 50 μL of PBS with 2% FBS. Next, the cells were diluted with an equal volume of 2× stock of the test bispecific binding molecule. The cells and antibody were co-incubated on ice for 20 min. The cells were then washed 3 times with 300 μL of FACS buffer and were resuspended in 100 μL of anti-human Fc-PE conjugate antibody (Invitrogen cat. #12499882) and incubated on ice with reduced light for 20 min. Subsequently, the cells were washed 3 times with 300 μL of FACS buffer and fixed with 2% paraformaldehyde for 10 min at 25° C. The cells then were washed 2 times with 300 μL of FACS buffer and analyzed on a Miltenyi MACSQuant Analyzer. 
     ROR1 Binding Assays Using Recombinant ROR1-ECD and ELISA 
     The binding of bispecific binding molecules to recombinant ROR1 was assessed by ELISA using two different configurations. In the first configuration, ROR1 protein was immobilized on 96-well plates and the bispecific constructs were titrated (details below). The bispecific binding molecules were also characterized for ROR1 binding using a second configuration in which the bispecific binding molecules were immobilized on the 96-well plates and soluble biotinylated ROR1 (b-ROR1) was titrated (details below). 
     Immobilized ROR1 ELISA 
     A 96-well Costar-3366 plate was coated with 50 μL/well of 2 μg/mL human TL1A (Acro Biosystems cat. #R01-H522Y) in PBS overnight at 4° C. The plate was rinsed once with PBS containing 0.05% Tween 20 (PBS-T) and blocked with 100 μL/well of 5% non-fat milk in PBS (5% M-P) for 1 h at 25° C. Antibody samples were serially diluted 2-fold using 5% M-P and were incubated for 1 h at 25° C. (50 μL/well). The plate was washed three times with PBS-T and 50 μL/well anti-human kappa, HRP conjugate (Southern Biotech cat. #2060-05) diluted 10,000-fold in 5% M-P was added for 1 h at 25° C. The plate was washed three times with PBS-T, developed with 50 μL/well 1-Step Ultra TMB-ELISA (Thermo Scientific cat. #34028). The reaction was terminated by the addition of 2 N H 2 SO 4  and the A450 was determined using a Spectramax plate reader. 
     Soluble ROR1 ESA 
     To biotinylate ROR1, 200 μg of human ROR1 (Acro Biosystems cat. #R01-H522Y) was resuspended in 2 mL water to 100 μg/mL and was then combined with EZ-Link Sulfo-NHS-LC-Biotin (Thermo Scientific cat. #21327) at a 1:5 molar ratio and incubated at 25° C. for 2 h. The reaction was terminated by the addition of 31 μL of 750 mM arginine hydrochloride and was stored at 4° C. 
     To measure the binding of bispecific constructs to soluble ROR1, a 96-well Costar-3366 plate was coated with 50 μL/well of 2 μg/mL goat anti-human kappa (Southern Biotech cat. #2060-01) in PBS overnight at 4° C. The plate was rinsed once with PBS-T, blocked with 100 μL/well 5% M-P for 1 h at 25° C., rinsed once with PBS-T, and 2 μg/mL of the bispecific binding molecule was added and incubated for 1 h at 25° C. The plate was washed three times with PBS-T. Biotinylated ROR1 was diluted serially, 3-fold in 5% M-P and was incubated for 1 h at 25° C. (50 μL/well). The plate was washed three times with PBS-T. To detect the binding of b-ROR1, 50 μL/well Neutravidin-HRP (Pierce cat. #31030) diluted 1:5000 in 1% BSA-PBS was added for 1 h at 25° C. The plate was washed three times with PBS-T, then developed with 50 μL/well 1-Step Ultra TMB-ELISA (Thermo Scientific cat. #34028). The reaction was terminated by the addition of 2 N H 2 SO 4  and the A450 was determined using a Spectramax plate reader. 
     Results 
     Three anti-ROR1 Fab variants, each differing from the parental antibody by a single amino acid in H-CDR2, were characterized for binding to human ROR using ELISA-based screening and live cell binding. Two of the variants, T32A and T32E, displayed higher affinity than the parental Fab ( FIG. 2 , Panel A, open circles and squares versus closed circles) while the other variant, W110Y, displayed lower affinity ( FIG. 2 , Panel A, triangles). The relative affinities of these variants were further characterized using live ROR1-transfected MEC cells. Similar to the ELISA-based screen, variants T32A and T32E displayed higher affinity ( FIG. 2 , Panel B, open circles and squares versus closed circles) while W110Y had diminished binding ( FIG. 2 , Panel B, triangles). No binding of any of the variants was detected when control empty vector transfected MEC cells were used (not shown), demonstrating the specificity of the variants for RORL. The relative binding strengths of the variants were very similar, regardless of the assay format. For example, the T32A variant was 4- to 4.7-fold higher affinity than the parental antibody while the W110Y variant was 5.9- to 6.8-fold lower affinity than the parental antibody. These very closely related variants differ from one another by one to two amino acids, display a 27-fold range of binding activity to ROR1, and enable the design of anti-ROR1/anti-CD3 bispecific binding molecules with a range of affinities for ROR1 as well as CD3. 
     Next, two additional anti-ROR1 Fab variants, each containing a distinct light chain CDR mutation combined with the heavy chain T32A mutation, were characterized for binding to human ROR using a modified version of the ELISA-based screen described previously. Specifically, the first wash step following the binding of the Fabs to immobilized ROR1 was altered by placing the plates in a large volume of PBS-T for a prolonged one hour dissociation step. This enabled variants with slow dissociation rates to be distinguished from one another. Using the modified ELISA, two variants, T32A (HC)+A25P (LC) and T32A (HC)+T69R (LC) displayed stronger binding than T32A ( FIG. 3 ). As described previously, the T32A variant displayed &gt;5-fold improvement in binding relative to the parental (WT), while T32A (HC)+A25P (LC) and T32A (HC)+T69R (LC) displayed further improvements in binding relative to the parental Fab (&gt;8- and &gt;13-fold, respectively). These very closely related variants differ from one another by 1-3 amino acids, display an 80- to 90-fold range of binding activity to ROR1, and enable the design of anti-ROR1/anti-CD3 bispecific binding molecules with a range of affinities for ROR1 as well as CD3. 
     The bispecific binding molecules were tested for ROR binding using three assays: (1) binding to live cells and detection by flow cytometry, (2) binding to immobilized ROR1 as determined by ELISA, and (3) binding to soluble, biotinylated ROR as determined by ELISA. Regardless of the screening format employed, all constructs bound ROR1 selectively ( FIGS. 4-7 ). 
     Selectivity for ROR was demonstrated by measuring binding to ROR1-transfected MEC cells and control MEC cells. Binding of the bispecific binding molecules to ROR1-transfected cells was concentration dependent ( FIG. 4 , Panel A) and no binding to the control cells was observed at any concentration ( FIG. 4 , Panel B). Non-specific human IgG was included as a control (“Control”) for both cell lines. 
     Variation in the binding strength of the bispecific constructs to ROR1-transfected MEC cells was observed ( FIG. 4 , Panel A). For example, ROR1 bivalent constructs bound more tightly than ROR monovalent constructs ( FIG. 4 , Panel A, compare constructs 1-3 and 7-9 with 13-15). This difference in binding strength was most apparent at lower concentrations (&lt;100 ng/mL). 
     The influence of ROR expression levels on binding of the bispecific constructs was assessed by flow cytometry using JeKo-1 cells. JeKo-1 cells express lower levels of ROR (˜13,000 copies/cell) than the ROR1-transfected MEC cells (˜56,000 copies/cell). All constructs bound JeKo-1 cells ( FIG. 5 ). Relative binding trends observed using the ROR1-transfected MEC cells were observed with JeKo-1 cells. Specifically, monovalent ROR1 constructs generally bound more weakly than the bivalent constructs ( FIG. 5 , Panel A, compare constructs 14 and 15 with other constructs;  FIG. 5 , Panel C, compare constructs 15-17 with other constructs). 
     Next, the binding of bispecific binding molecules to ROR was characterized by ELISA using recombinantly-expressed extracellular domain of RORL. ROR was immobilized on a microtiter plate, the bispecific binding molecules were titrated, and binding was quantitated with an anti-human kappa-HRP reagent. Consistent with the cell binding data, all constructs bound ROR1 in a concentration-dependent manner ( FIG. 6 ). Moreover, monovalent ROR1 constructs 13-15 bound less tightly than all but two of the bivalent constructs. The binding activities of the bivalent bispecific binding molecules were similar to the parental anti-ROR1 IgG (Control), demonstrating that appending scFv domains to the Ig molecule did not inhibit ROR1 binding. The relative affinities of the bispecific constructs tested in this format are summarized in Table 4. 
     The stronger binding observed with bivalent constructs versus monovalent constructs in cell assays and ELISAs in which the antigen is immobilized is consistent with an avidity effect. To determine if this was the case, binding to soluble monomeric ROR1 was assessed by immobilizing the bispecific binding molecules on a microtiter plate coated with goat anti-human kappa antibody and titrating biotinylated RORL. All bispecific binding molecules were active in this format ( FIG. 7 ), and in most cases, there were no notable differences between monovalent and bivalent constructs. These results are consistent with an avidity effect, depending on the assay format used. Weaker binding was observed with both variants in which the anti-CD3 scFv was amended to the amino terminus of the heavy or light chain (constructs 19 and 20, respectively), suggesting that placement of the CD3 paratope in close proximity to the ROR1 paratope may inhibit ROR1 binding to some extent. 
     Bispecific binding molecule constructs containing a higher affinity ROR1 binding domain (constructs 16-18) bound biotinylated ROR1 with higher affinity than the corresponding constructs that utilized the wild-type (lower affinity) ROR1 binding domain (constructs 9, 19, 20). Bispecific construct 18 (bivalent, higher affinity ROR1) bound more tightly than the corresponding construct 9 (bivalent, lower affinity ROR1). Likewise, bispecific constructs 16 and 17 (monovalent, higher affinity ROR1) bound more tightly than construct 15 (monovalent, lower affinity ROR1). These data are summarized in Table 4. Additionally, bispecific binding molecules with the higher affinity ROR1 binding domain bound soluble ROR1 with higher affinity than the parental IgG (Control). 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Bispecific Binding Molecule Affinities for ROR1 
               
            
           
           
               
               
               
            
               
                   
                   
                 K D  (nM) 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Immobilized 
                 Soluble 
               
               
                   
                 Construct 
                 ROR1 
                 b-ROR1 
               
               
                   
                   
               
               
                   
                  1 
                 0.200 
                 0.193 
               
               
                   
                  2 
                 0.041 
                 0.129 
               
               
                   
                  3 
                 0.233 
                 0.147 
               
               
                   
                  4 
                 0.085 
                 0.105 
               
               
                   
                  5 
                 0.055 
                 0.070 
               
               
                   
                  6 
                 0.033 
                 0.082 
               
               
                   
                  7 
                 0.050 
                 0.118 
               
               
                   
                  8 
                 0.098 
                 0.151 
               
               
                   
                  9 
                 0.158 
                 0.268, 0.229 
               
               
                   
                 10 
                 0.144 
                 0.094 
               
               
                   
                 11 
                 0.092 
                 0.073 
               
               
                   
                 12 
                 0.116 
                 0.086 
               
               
                   
                 13 
                 0.194 
                 0.226 
               
               
                   
                 14 
                 0.408 
                 0.109 
               
               
                   
                 15 
                 0.301 
                 0.157 
               
               
                   
                 16 
                   
                 0.057 
               
               
                   
                 17 
                   
                 0.068 
               
               
                   
                 18 
                   
                 0.048 
               
               
                   
                 19 
                   
                 0.200 
               
               
                   
                 20 
                   
                 0.366 
               
               
                   
                 Control 
                 0.037 
                 0.158, 0.145 
               
               
                   
                   
               
            
           
         
       
     
     Example 3: ROR1 Internalization by Anti-ROR1/Anti-CD3 Bispecific Binding Molecules 
     Internalization and recycling of ROR1 and bispecific binding molecules that recognize ROR1 may impact therapeutic efficacy in vivo. For example, binding, internalization and degradation of ROR1 prior to engagement of T cells might be expected to diminish cytotoxicity. Anti-ROR1/anti-CD3 bispecific binding molecules with five distinct configurations were characterized for binding and internalization. 
     Simultaneous with characterizing the internalization of the various bispecific constructs, cell surface expression of ROR1 was examined using two different ROR1 antibodies. One antibody (UC961) recognizes the same ROR1 epitope as the bispecific binding molecules while the other (4A5) recognizes a non-overlapping ROR1 epitope. 
     In addition, cell surface binding of bispecific binding molecules was assessed following a 24 h incubation at 37° C. to determine if prolonged exposure influenced cell surface levels of the various binding molecules. 
     The internalization of ROR1 bispecific binding molecules and the recycling/re-expression of ROR1 was characterized using ROR1-transfected MEC cells and flow cytometry. 
     Materials and Methods 
     Measurement of Internalization of Bispecific Binding Molecules 
     Internalization of bispecific binding molecules was measured using a pulse-chase methodology that quantitates non-internalized, cell surface antibody at 0, 30, 60, 120, 180, and 240 minutes using flow cytometry. ROR1-transfected MEC cells were washed with cold PBS and resuspended at 1×10 7  per mL in cold incubation buffer (RPMI with 2% FBS—Fisher/Gibco cat. #16140071). Then, 3.5×10 6  cells were aliquoted to microcentrifuge tubes for each bispecific construct tested. An equal volume (350 μL) of bispecific binding molecule was combined with the cells to make a final concentration of 30 μg/mL. Based on previous binding studies, it was expected that 30 μg/mL would be saturating for the higher affinity/avidity of the bivalent ROR1 constructs (constructs 1-12). Cells and antibody were incubated on ice for 20 minutes, washed five times with 1 mL of cold FACS buffer (PBS with 2% FBS), and resuspended in 1.4 mL of incubation buffer. Subsequently, the samples were incubated at 37° C. for 0, 30, 60, 120, 180, and 240 minutes after which time 200 μL of each sample was transferred to ice to halt internalization. 
     Samples for each construct and timepoint were split in half (100 μL each) and spun down. Half of the samples were resuspended in 100 μL secondary antibody (goat anti-human IgG-PE, Fc-gamma specific—eBiosciences cat. #12-4998) to detect bound bispecific constructs. The other half was stained with 100 μL cocktail of UC961-PE and 4A5-AlexaFluor647. UC961 binds the same epitope as the bispecific constructs, thus detecting free ROR1 not bound by the bispecific binding molecules. 4A5 binds ROR1 at a different epitope, and therefore does not compete with the bispecific binding molecules for binding. Thus, 4A5 detects total cell surface ROR1 (bound and free). Both staining sets remained in incubation buffer for 20 minutes on ice in the dark. Cells were washed three times with FACS buffer and resuspended in 100 μL of fix buffer (2% paraformaldehyde in PBS) for 10 minutes at 25° C. Subsequently, fixed cells were washed once with FACS buffer and analyzed. 
     The median fluorescent intensity (MFI) was quantified for each stain. Several control conditions were used. The PE and A1647 MFI were measured for unstained control cells to use for background fluorescence subtraction. Cells not exposed to the bispecific constructs were stained with secondary antibody PE, to account for non-specific staining of the secondary antibody (secondary negative control), and with UC961-PE to obtain maximal UC961 binding control. Quantification of surface bispecific binding molecule, unoccupied cell surface ROR1 epitope, and total ROR1 was performed as follows: 
     
       
         
           
             
               Surface 
               ⁢ 
               
                   
               
               ⁢ 
               biAb 
             
             = 
             
               
                 [ 
                 
                   
                     ( 
                     
                       PE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       secondary 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       at 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       time 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       point 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       x 
                     
                     ) 
                   
                   - 
                   
                     
 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       PE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       secondary 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       negative 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       control 
                     
                     ) 
                   
                 
                 ] 
               
               
                 [ 
                 
                   
                     ( 
                     
                       PE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       secondary 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       at 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       time 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       point 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       0 
                     
                     ) 
                   
                   - 
                   
                     
 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       PE 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       secondary 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       negative 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       control 
                     
                     ) 
                   
                 
                 ] 
               
             
           
         
       
       
         
           
             
               Total 
               ⁢ 
               
                   
               
               ⁢ 
               ROR1 
             
             = 
             
               
                 [ 
                 
                   
                     ( 
                     
                       A 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1647 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       4 
                       ⁢ 
                       A 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       5 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       at 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       time 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       point 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       x 
                     
                     ) 
                   
                   - 
                   
                     
 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     
                       A 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1647 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       MFI 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       of 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       unstained 
                       ⁢ 
                       
                           
                       
                       ⁢ 
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     Results 
     Previous experiments with the anti-ROR1 antibody used for constructing the bispecific binding molecules described herein demonstrated: (1) that the antibody was rapidly internalized, and (2) ROR1 re-appeared on the cell surface without bound antibody. This cell surface expression was either a result of ROR1 recycling from endosomal compartments or reflects rapid upregulation of ROR1 through de novo synthesis or trafficking of intracellular stores (see, e.g., U.S. Patent Publication 2018/0369406). The different bispecific constructs displayed variable internalization and ROR1 recycling/re-expression patterns ( FIG. 8  and  FIG. 9 ). 
     Placement of anti-CD3 scFv at the carboxy-terminus of the heavy chain (configuration A, construct 1) led to rapid internalization ( FIG. 8 , Panel A, circles). At time zero, the available ROR1 bispecific epitope was saturated, since no free epitope was detected. ROR1 was not recycled to the cell surface or re-expressed at significant levels during the experimental time course, as total ROR1 surface levels decreased ( FIG. 8 , Panel A, squares) and there was no detection of the free ROR1 epitope recognized by the bispecific binding molecule ( FIG. 8 , Panel A, triangles). These data are consistent with internalization of the bispecific binding molecule-ROR1 complex and trafficking to lysosomes. Very similar internalization and trafficking was observed with bispecific binding molecule constructs 2 and 3 (not shown). 
     Placement of anti-CD3 scFv at the carboxy-terminus of the light chain (configuration B, construct 7) inhibited internalization significantly ( FIG. 8 , Panel B, compare extent of internalization relative to construct 3 in  FIG. 8 , Panel A). At time 0, the construct has fully saturated its epitope. Total cell surface ROR1 levels appeared relatively constant ( FIG. 8 , Panel B, squares). In addition, the free ROR1 epitope recognized by the bispecific increased in a time-dependent manner ( FIG. 8 , Panel B, triangles), consistent with either dissociation of the bispecific binding molecule from the cell surface or recycling/re-expression of RORL. Very similar internalization and trafficking was observed with bispecific binding molecule constructs 8 and 9 (not shown). 
     Monovalent anti-ROR1 (configuration C, construct 13) also was not internalized efficiently ( FIG. 8 , Panel C). Previous studies demonstrated that binding of bivalent constructs was saturating at 30 μg/mL ( FIG. 4 , Panel A and  FIG. 5 ). However, binding of monovalent anti-ROR1 bispecific binding molecules at 30 μg/mL did not appear to saturate cell surface ROR1 in this experiment. At time 0 the binding extent of construct 13 was only ˜80% of that of the corresponding saturated MFI of constructs 1 and 7 at time 0 ( FIG. 8 , Panel C, compare circles with squares at time 0). Additionally, free ROR1 epitope recognized by construct 13 was also detected at time 0 ( FIG. 8 , Panel C, triangles). In summary, the levels of monovalent bispecific binding molecule construct 13, total cell surface ROR1 and unoccupied bispecific epitope all remained relatively constant over the duration of the experiment. Collectively, these data are consistent with little internalization of the bispecific binding molecule 13. Very similar internalization and trafficking was observed with construct 15 (not shown). 
     Placement of anti-CD3 scFv at the amino-terminus of one heavy chain (configuration D, construct 19) led to partial internalization ( FIG. 9 , Panel A, circles). ROR1 was recycled to the cell surface or re-expressed at significant levels during the experimental time course, as total ROR1 surface levels increased ( FIG. 9 , Panel A, squares) and there was increased, time-dependent detection of the ROR1 epitope recognized by the bispecific binding molecule ( FIG. 9 , Panel A, triangles). Placement of an anti-CD3 scFv moiety at the amino-terminus of one heavy chain resulted in internalization and trafficking very similar to bispecific binding molecules with configuration B (anti-CD3 scFv fused to the carboxy-terminus of the light chain). 
     Placement of anti-CD3 scFv at the amino-terminus of the light chain (configuration E, construct 20) led to partial internalization ( FIG. 9 , Panel B, circles). ROR1 was recycled to the cell surface or re-expressed at significant levels during the experimental time course, as total ROR1 surface levels increased ( FIG. 9 , Panel B, squares) and there was increased, time-dependent detection of the ROR1 epitope recognized by the bispecific binding molecule ( FIG. 9 , Panel B, triangles). Placement of an anti-CD3 scFv moiety at the amino-terminus of the light chain resulted in internalization and trafficking very similar to bispecific binding molecules with configuration B (anti-CD3 scFv fused to the carboxy-terminus of the light chain). 
     To determine the long term impact of ROR1 trafficking and expression on the levels of bispecific binding molecules bound to the cell surface, cells were incubated with the bispecific binding molecule for 24 h, washed, and cell surface bispecific binding molecule was measured. Quantitation of surface bispecific binding molecule after 24 h incubation revealed that bispecific binding molecules with anti-CD3 scFv fused to the carboxy-terminus of the heavy chain ( FIG. 10 , construct 1, circles) were present at lower levels than bispecific binding molecules with the anti-CD3 scFv fused to the carboxy-terminus of the light chain ( FIG. 10 , construct 7, squares) or bispecific binding molecules with the anti-CD3 scFv fused to the amino-terminus of the Fc ( FIG. 10 , construct 13, triangles). Diminished cell surface levels of constructs in which anti-CD3 scFv is fused to the carboxy-terminus of the heavy chain, but not other bispecific configurations, suggests down-regulation of surface ROR1 and is consistent with the observations made in the internalization experiments ( FIG. 8 ). 
     Example 4: CD3 Binding and Internalization of Anti-ROR1/Anti-CD3 Bispecific Binding 
     Molecules 
     The number of TCR-CD3 complexes on the surface of T cells reflects the combination of synthesis and secretion of new protein, internalization, recycling and degradation. Treatment with anti-CD3 antibody OKT3 has been shown to selectively remove CD3 from the surface by internalization. 
     Three anti-CD3 sequences were used as scFv constructs in anti-ROR1/anti-CD3 bispecific binding molecules. Two of the sequences are different humanized versions of OKT3 (Ab8 and Ab9) while the third sequence is a third party humanized version of a different anti-CD3 antibody, SP34 (Ab10). As noted above, OKT3 and SP34 bind distinct epitopes, and anti-CD3 antibodies have been classified based on distinct characteristics of their epitopes (Tunnacliffe et al.,  International Immunology  1:546-550 (1989)). Using this system, SP34 is classified as Group I while OKT3 is classified as Group II. The SP34-based sequence, but not the OKT3-based sequences, are expected to be cross-reactive with cynomolgus CD3. 
     The various CD3 paratopes were evaluated in five distinct configurations ( FIG. 1 , A-E) and the binding of monovalent anti-CD3 bispecific constructs ( FIGS. 1 , C and D) was compared with certain bivalent anti-CD3 constructs ( FIGS. 1 , A, B and E). Disulfide-stabilized versions of all three scFv sequences were also evaluated in the various bispecific configurations. 
     The internalization of the various bispecific constructs in the absence of ROR1 engagement was assessed. The binding and internalization of the bispecific binding molecules was characterized using Jurkat cells and flow cytometry. 
     Materials and Methods 
     CD3 Binding Assay 
     To quantitate CD3 binding, 2.5E5 Jurkat cells were used for each condition. A 2× stock of the cells was made by resuspending the cells to 5E6/mL by placing in 50 μL of PBS with 2% FBS. Next, the cells were diluted with an equal volume of 2× stock of the test bispecific binding molecule. The cells and antibody were co-incubated on ice for 20 min. The cells were then washed 3 times with 300 μL of FACS buffer and were resuspended in 100 μL of goat anti-human Fc-PE conjugate antibody (Invitrogen cat. #12499882) at 1:500 dilution and incubated on ice with reduced light for 20 min. The cells were then washed 3 times with 300 μL of FACS buffer and fixed with 2% paraformaldehyde for 10 min at 25° C. The cells were washed 2 times with 300 μL of FACS buffer and analyzed on a Miltenyi MACSQuant Analyzer. 
     CD3 Internalization Assay 
     To quantitate internalization of the bispecific binding molecules, 2.5E5 Jurkat cells were co-incubated with 1 μg/mL of the bispecific binding molecule on ice for 20 min. The cells were then washed 3 times 300 μL with ice-cold FACS buffer and were resuspended in culture media and incubated at 37° C. At various times, cells were removed, washed with 300 μL ice-cold FACS buffer and processed as described above. 
     Results 
     Five different bispecific configurations ( FIG. 1 ) were evaluated. CD3 binding was preserved with both OKT3- and SP34-based sequences in all the bispecific configurations tested, as demonstrated by binding to Jurkat cells. The constructs bound to varying extents ( FIG. 11  and  FIG. 12 ). 
     For all bispecific configurations tested with either OKT3 and SP34 sequences (constructs 1-15), the OKT3-based sequences bound with higher affinity than the SP34-based sequences. For example, constructs 1 and 2 bound more tightly than 3 ( FIG. 11 , Panel A), constructs 7 and 8 bound more tightly than 9 ( FIG. 11 , Panel B) and constructs 13 and 14 bound more tightly than 15 ( FIG. 11 , Panel C). Non-specific human IgG was included as a control (“Control”). 
     Introduction of cysteine residues to create disulfide-stabilized variants of the anti-CD3 scFv did not negatively impact binding. Binding of the disulfide-stabilized variants was indistinguishable from the corresponding non-disulfide stabilized sequence ( FIG. 11 , Panel A, compare constructs 1-3 with 4-6, respectively and  FIG. 11 , Panel B, compare constructs 7-9 with 10-12, respectively). 
     The configuration of the bispecific binding molecule had a profound effect on the binding of the anti-CD3 scFv ( FIG. 12 ). The strongest binding to Jurkat cells was observed when the anti-CD3 scFv moiety was placed on the amino-terminus of the light chain ( FIG. 12 , Panel B, construct 20) or heavy chain ( FIG. 12 , Panel B, construct 19). Conversely, weaker binding was observed when the anti-CD3 scFv was placed at the carboxy-terminus of the light chain ( FIG. 12 , Panel B, constructs 9 and 18). A single anti-CD3 scFv moiety placed at the amino-terminus of one heavy chain (monovalent CD3 binding;  FIG. 12 , Panel B, construct 19) bound as well, or better than, placement of two anti-CD3 scFv moieties at the carboxy-terminus of the heavy chain (bivalent CD3 binding;  FIG. 12 , Panel B, construct 3) or light chain (bivalent CD3 binding;  FIG. 12 , Panel B, constructs 9 and 18). Non-specific human IgG was included as a control in one experiment ( FIG. 12 , Panel A, “Control”) while an unrelated ROR1 x CD3 bispecific construct (U.S. Patent Publication 2017/0233472; SEQ ID NOs: 111-113) was included as a control in the second experiment ( FIG. 12 , Panel B, “control 1”). 
     Similar trends were observed with a subset of these bispecific configurations using OKT3 sequences. Specifically, monovalent anti-CD3 scFv fused to the amino-terminus of the Fc bound strongest ( FIG. 12 , Panel A, construct 13), followed by constructs in which the scFv was fused to the carboxy-terminus of the heavy chain ( FIG. 12 , Panel A, construct 1), followed by constructs in which the scFv was fused to the carboxy-terminus of the light chain ( FIG. 12 , Panel A, construct 7). 
     It is noteworthy that the configuration of the bispecific binding molecule appears to be a more important determinant of CD3 binding strength than the CD3 paratope valency. This surprising effect is highlighted by the observation that monovalent anti-CD3 constructs fused to the amino terminus of the heavy chain ( FIG. 12 , Panel B, construct 19) or Fc ( FIG. 12 , Panel A, construct 13 and  FIG. 12 , Panel B, constructs 15 and 16) bound as well or better than bivalent anti-CD3 constructs fused to the carboxy-terminus of the heavy and light chains ( FIG. 12 , Panel B, constructs 3, 9 and 18). 
     Collectively, these data demonstrate that there are three different approaches to modulating the strength of CD3 binding. First, SP34- and OKT3-based sequences display differing binding strengths when compared to one another in the same bispecific formats. Second, the binding strength of both SP34- and OKT3-based sequences is influenced by the configuration of the bispecific binding molecule. Finally, the use of heteromeric Fc constructs enables either monovalent or bivalent anti-CD3 bispecific binding molecules. 
     T cell activation by anti-CD3 antibodies may result in increased internalization of CD3. Once internalized, the CD3 may enter a recycling pathway and be re-expressed at the cell surface or may be sorted to the lysosomes and degraded. Internalization and degradation of CD3 induced by bispecific binding molecule in the absence of tumor antigen (ROR1) engagement may inhibit the cytotoxic activity of the bispecific binding molecule in vivo. Consequently, the bispecific binding molecules were characterized for internalization following binding to CD3 in the absence of ROR1 ( FIG. 13 ). 
     Following the binding of bispecific binding molecule and washing at 4° C., Jurkat cells were incubated at 37° C. Subsequently, the amount of bispecific binding molecule on the cell surface was quantitated at various time points. Because the bispecific binding molecules initially bound with different strengths ( FIG. 11  and  FIG. 12 ), the internalization was reported as a percentage of binding observed at time 0. The level of surface bispecific binding molecule quantitated in this manner reflects a combination of internalization and dissociation. Nonetheless, for reasons outlined below, it appeared that the primary factor influencing surface levels was internalization and not dissociation of the bispecific binding molecules. 
     The level of surface bispecific binding molecule diminished in a time-dependent manner for all bispecific constructs tested, though the extent of loss varied. Rapid internalization (&gt;50%) was observed within the first 30 min for eight of nine constructs tested, followed by a slower, but continuous internalization over the next 3.5 h. Construct 9, consisting of an SP34-based sequence fused to the carboxy-terminus of the light chain, was internalized the least over the duration of the experiment, with approximately 50% of the bispecific binding molecule still detectable on the cell surface after 4 h. In addition, constructs 1 and 3, consisting of the anti-CD3 scFv moiety fused to the carboxy-terminus of the heavy chain, displayed intermediate internalization, with ˜20% still detectable on the cell surface after 4 h incubation. 
     As discussed previously, it is possible that the decreased staining of cell surface bispecific binding molecule observed over time reflects dissociation of the bispecific binding molecule from the surface as opposed to internalization. However, two of the bispecific constructs that displayed the least loss of signal over time, constructs 3 and 9, were among the weakest binding constructs characterized ( FIG. 11 , Panel A and Panel B, respectively) while the binding of construct 13, which displayed very strong binding at time 0 ( FIG. 11 , Panel C), stained weakly at 4 h (8% of initial signal). Collectively, these data suggest that certain configurations consisting of SP34-based anti-CD3 scFv moieties may internalize to a lesser extent than configurations consisting of OKT3-based scFv moieties. 
     Example 5: Redirected T Cell Toxicity of Anti-ROR1/Anti-CD3 Bispecific Binding Molecules In Vitro 
     The twenty anti-ROR1/anti-CD3 bispecific binding molecules were tested to evaluate the impact of multiple parameters on antibody potency in T-cell mediated cytotoxicity assays. Variables examined included anti-CD3 epitope and valency, anti-ROR1 affinity and valency, and various configurations of the CD3 and ROR1 binding components. 
     The killing activity of the constructs was tested against a panel of hematological and solid tumor cancer cells with varying levels of ROR1 expression. In addition to characterizing the killing activity of the bispecific binding molecules, activation of T cells was assessed using CD69 as a marker. Cytokine release by activated T cells was also characterized. 
     Materials and Methods 
     Cytotoxicity Assay with Human PBMCs 
     For the cytotoxicity assay, target cells were resuspended to 4E5 cells/mL in RPMI (without phenol red), 10% FBS containing penicillin-streptomycin. Subsequently, 2E4 cells/well (50 μL/well) were transferred to a 96-well plate and placed in an incubator at 37° C. for 1 h. Round bottom plates were used for suspension cells and flat bottom plates for adherent cell lines. Human PBMCs were isolated as described below. The PBMCs were resuspended to 2E6 cells/mL, and subsequently, 2E5 cells/well (100 μL/well) were added to the wells containing the target cells. Unless indicated otherwise, the ratio of PBMCs (effector cells) to tumor cells (target) used was 10:1 (E:T ratio). The target cells and PBMCs were mixed and placed in an incubator at 37° C. for 1 h. The bispecific binding molecules were diluted to the appropriate concentration in media and 50 μL was added to the mixture of target cells and PBMCs and then placed in an incubator for 24 h at 37° C. The following controls were included for each experiment: (1) media only (Media), (2) media adjusted for lysis buffer (Adj), (3) PBMCs only (PBMCs), (4) target cell only for spontaneous release of LDH (SR), (5) target cell only for maximal release of LDH (MR), and (6) target cells and PBMCs without bispecific binding molecule (AICC). 
     Isolation of PBMCs 
     The lower chamber of SepMate-50 (StemCell Technologies) conical tubes was filled with 15 mL of Ficoll. Blood was obtained from de-identified normal donors in heparin blood collection tubes and was mixed in a 1:1 ratio with sterile PBS at 25° C. The diluted blood was layered on the top chamber of the SepMate-50 tubes and was centrifuged at 1200×g for 15 min at 25° C. with brakes. To obtain the PBMCs (top chamber contents), the SepMate-50 tubes were inverted quickly into a fresh 50 mL conical tube. The cells were then washed three times with cold 5% FBS in PBS by centrifugation at 500×g for 3 minutes. Finally, the cells were resuspended in 10 mL of media (RPMI without phenol red, 10% FBS containing penicillin-streptomycin) and an aliquot was removed for cell count. Cells were then used for plating the cytotoxicity assay. 
     Quantitation of LDH Release 
     To quantitate LDH release after 24 h incubation, 20 μL of 10× lysis buffer was added to the Adj and MR wells and the content of each well was transferred to a V-bottom 96 well plate and spun down at 500 x g for 5 minutes. Subsequently, 170 μL of supernatant was transferred to a separate 96 well plate to use for subsequent assays. In a fresh clear bottom 96 well plate, 50 μL of supernatant was combined with 50 μL of CytoTox 96 Non-Radioactive Cytotoxicity Assay (Promega cat. #G1780) and the plate was incubated in the dark at 25° C. for 30 minutes. Finally, 50 μL of stop solution was added prior to reading the absorbance at 490 nm. The % LDH release was calculated per manufacturer&#39;s instructions. 
     Assessment of T Cell Activation 
     Up-regulation of CD69 was used to characterize the early activation of the T cells. Quantitation of CD69 was performed using flow cytometry. Briefly, the pelleted cells were fixed by resuspending in 100 μL of 2% PFA in PBS and incubating for 10 min at 25° C. The cells were washed twice with 300 μL of PBS, resuspended in 150 μL of PBS, and were stored at 4° C. in the dark until use. Subsequently, the cells were collected by centrifugation and were resuspended in 100 μL of stain cocktail and incubated for 20 min at 4° C. in the dark. The stain cocktail consisted of Pacific Blue anti-human CD8 clone SK1 (BioLegend cat. #344717) diluted 1:75, PECy7 anti-human CD69 clone FN50 (BioLegend cat. #310911) diluted 1:500, and AlexaFluor647 mouse anti-human ROR1 clone 4A5 diluted 1:500 in PBS. The cells were then washed three times with 300 μL of cold PBS and were resuspended in 150 μL of 2% FBS in PBS. The samples were analyzed on a Mitenyi MACSQuant Analyzer. 
     Quantitation of Cytokine Release from PBMCs in Redirected T-cell Assay 
     To measure cytokine release, the MSD® V-PLEX Cytokine Panel 1 Human Kit was used to concurrently measure IFN-γ, IL-2, IL-4, IL-6, IL-10 and TNF-α. The assay was conducted per manufacturer&#39;s instructions. Briefly, the V-plex Cytokine Panel 1 plate was washed 3 times with 150 μL/well of Wash Buffer (PBS with 0.05% Tween-20). Next, 50 μL of diluted samples and calibrators were added per well. The plate was sealed with an adhesive plate seal and incubated on a shaker overnight at 4° C., 500 rpm. The following day the plate was washed 3 times with 150 μL/well of Wash Buffer and incubated with 25 μL of detection antibody solution on a shaker for 2 hours at room temperature. The plate was washed 3 more times with Wash Buffer. Lastly, 150 uL of Read Buffer T was added before analysis using the MSD instrument. 
     Results 
     Antigen-dependent killing of ROR1-transfected MEC cells was observed with the majority of bispecific constructs tested, though the relative potencies varied. Representative titration profiles are shown in  FIG. 14 , Panel A (constructs with configurations A, B and C) and in  FIG. 15 , Panel A (constructs with configurations A, B, C, D and E). The titration profiles of constructs 2, 8, and 14 (not shown) were similar to the titration profiles of constructs 1, 7, and 13, respectively. 
     As expected, the absolute potency of the bispecific binding molecules varied to some extent when different PBMC donors were used. Nonetheless, the relative potencies of the different constructs did not fluctuate significantly. For example, bispecific binding molecule construct 9 was consistently one of the most active and with ROR1-transfected MEC target cells displayed an EC 50  of &lt;0.1 ng/mL with one donor ( FIG. 14 , Panel A) and 1.1 ng/mL with a second donor ( FIG. 15 , Panel A). 
     Constructs 1-3, 7-9, and 13-15 all demonstrated selective killing at 1 μg/mL (5 nM for constructs 1-3 and 7-9, 8 nM for constructs 13-15 ( FIG. 16 , black bars). The antigen dependence of the killing was demonstrated by the lack of LDH release in samples that did not contain target cells ( FIG. 16 , “PBMC”) or antibody ( FIG. 16 , “no biAb”) or when non-transfected MEC cells were used as target cells ( FIG. 16 , gray bars). In contrast, a control anti-CD19/anti-CD3 bispecific binding molecule (Creative Biolabs cat. #BSAB-L002) induced cytotoxicity of both ROR1-transfected and non-transfected MEC cells ( FIG. 16 , “CD19 x CD3”). Bispecific constructs 16-20 were not tested in this experiment. 
     Activation of T cells in the cultures was assessed by examining the upregulation of CD69, an early marker of T cell activation. Consistent with the cytotoxicity data, activation was observed with all constructs except for #17 and #19, at 1 μg/mL ( FIG. 14 , Panel B;  FIG. 15 , Panel B). For the more potent bispecific binding molecules, activation was observed at lower concentrations ( FIG. 14 , Panel B, compare 7 vs 3;  FIG. 15 , Panel B, compare 18 vs 3). 
     T cell activation, as assessed by increased CD69 expression, generally reflected the cytotoxic activity of the bispecific binding molecules. However, there were examples where CD69 activation was not directly correlated with cytotoxicity ( FIG. 19 , compare 7 and 9;  FIG. 20 , compare 7 versus 8 and 9). 
     Activation of the T cells was antigen-dependent ( FIG. 17 ). T cells co-cultured with ROR1-/CD19 +  MEC cells were activated in the presence of the control CD19 x CD3 bispecific binding molecule ( FIG. 17 , Panel A, left) but not in the presence of the ROR1 bispecific binding molecules ( FIG. 17 , Panel A, right). However, when T cells were co-cultured with ROR1-transfected MEC cells (ROR1*/CD19*) the T cells were activated in the presence of ROR1 bispecific binding molecules ( FIG. 17 , Panel B, right). These data demonstrate that ROR1 is required for activation of the T cells by the bispecific constructs characterized in this study. 
     Next, ROR1-dependent killing of different human target cells by the bispecific binding molecules was examined. ROR1-dependent killing of JeKo-1 cells, a mantle cell lymphoma cell line, was observed with all the bispecific binding molecules of configurations A, B, C and E, albeit with varying potencies. Representative titration profiles are shown in  FIG. 18 , Panel A (constructs 1-15) and  FIG. 19 , Panel A (constructs 16-20). Consistent with the observations made with ROR1-transfected MEC cells, activation of T cells generally reflected the relative cytotoxicity of the bispecific binding molecules ( FIG. 18 , Panel B;  FIG. 19 , Panel B). 
     A second mantle cell lymphoma cell line, Mino cells, was also tested as a target cell line. All three non-disulfide stabilized constructs with configuration B displayed potent activity towards Mino cells ( FIG. 20 , Panel A) with the SP34-based CD3 sequence (construct 9) being the most potent. Interestingly, construct 9 activated T cells (as determined by upregulation of CD69) less than the OKT3 based constructs ( FIG. 20 , Panel B). 
     Likewise, ROR1-dependent killing of the breast tumor cell line MDA-MB-468 was observed with varying potencies with bispecific configurations A, B, C and E. Representative titration profiles are shown in  FIG. 21 , Panel A (constructs 1-15) and  FIG. 22 , Panel A (constructs 16-20). Consistent with the observations made with ROR1-transfected MEC cells and JeKo-1 cells, activation of T cells generally reflected the relative cytotoxicity of the bispecific binding molecules ( FIG. 21 , Panel B;  FIG. 22 , Panel B). 
     The induction of cytokine release following the activation of T cells in the redirected killing of JeKo-1 cells, ROR1-transfected MEC cells, and mock-transfected (ROR1-) MEC cells was characterized. Representative dose-response graphs are shown for constructs 7, 9, 18, 20 and a control ROR1 x CD3 bispecific binding molecule (U.S. Patent Publication 2017/0233472). ( FIG. 23  (TNF-α),  FIG. 24  (IFN-γ),  FIG. 25  (IL-2),  FIG. 26  (IL-4),  FIG. 27  (IL-6),  FIG. 28  (IL-10)). Dose-dependent cytokine production (TNF-α, IFN-γ, IL-2, IL-4, IL-6 and IL-10) was observed with JeKo-1 cells (Panel A) and ROR1-transfected MEC cells (Panel B), but not with mock-transfected (ROR1-) MEC cells (Panel C), for all constructs tested. ROR1-transfected MEC cells express higher levels of ROR1 than JeKo-1 cells (Table 5) and were more sensitive to the bispecific binding molecules tested than the JeKo-1 cells, demonstrating the importance of target expression levels. Secretion of cytokines was dependent on the expression of ROR1. Incubation of 1 μg/mL of the constructs with mock-transfected (ROR1-) MEC cells (Panel C) did not induce secretion of any of the cytokines at levels significantly above background (no bispecific antibody control). By contrast, incubation of the ROR1 x CD3 bispecific binding molecule (“control 1”) with mock-transfected (ROR1-) MEC cells resulted in some secretion of the inflammatory cytokine IFN-γ ( FIG. 24 , Panel C). With the exception of IL-6, control 1 induced a higher overall level of cytokine secretion when tested with JeKo-1 cells. By contrast, all of the constructs, including control 1, induced similar levels of cytokine secretion when tested with the higher ROR-expressing transfected MEC cells. 
     A summary of the activity of some of the bispecific binding molecules versus various target cells is shown in Table 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Summary of Cell Lines Tested with Bispecific Constructs 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 ROR1 
                   
                 EC 50   
                 Max. LDH  
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Description 
                 Cell Line 
                 Count 
                 Construct 
                 ng/mL 
                 pM 
                 Release (%) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Controls 
                 MEC 
                 0 
                   
                   
                   
                   
               
               
                   
                 ROR1-transfected MEC 
                 56,000 
                 1 
                 11 
                 55 
                 42 
               
               
                   
                   
                   
                 2 
                 5.0 
                 25 
                 50 
               
               
                   
                   
                   
                 3 
                 4.9-10 
                 25-50 
                 14-45 
               
               
                   
                   
                   
                 7 
                 1.3 
                 6.5 
                 55 
               
               
                   
                   
                   
                 9 
                 0.1-1.1 
                 0.5-5.5 
                 29-57 
               
               
                   
                   
                   
                 13 
                 12 
                 96 
                 46 
               
               
                   
                   
                   
                 14 
                 5.0 
                 40 
                 48 
               
               
                   
                   
                   
                 15 
                 ND 
                 ND 
                 15-41 
               
               
                   
                   
                   
                 18 
                 3.5 
                 17 
                 34 
               
               
                   
                   
                   
                 20 
                 1.8 
                 9.0 
                 37 
               
               
                 Mantle cell 
                 Mino 
                 6,689 
                 7 
                 0.97 
                 4.9 
                 50 
               
               
                   
                   
                   
                 8 
                 0.95 
                 4.8 
                 53 
               
               
                   
                   
                   
                 9 
                 0.75 
                 3.8 
                 75 
               
               
                   
                 JeKo-1 
                 13,000 
                 8 
                 1.619 
                 8.1 
                 58 
               
               
                   
                   
                   
                 9 
                 1.705 
                 8.5 
                 60 
               
               
                 Breast 
                 MDA-MB-468 
                 25,812 
                 9 
                 5.553 
                 27.8 
                 30 
               
               
                   
                 HCC1937 
                 13,521 
                 9 
                 ND 
                 ND 
                 12 
               
               
                   
                 MCF7 
                 25 
                 9 
                 Inactive 
                   
                 0 
               
               
                 Lung 
                 NCI-H1975 
                 20,291 
                 9 
                 2.302 
                 11.5 
                 44 
               
               
                   
                 A549 
                 18,133 
                 8 
                 3.394 
                 17.1 
                 8 
               
               
                   
                   
                   
                 9 
                 9.951 
                 49.8 
                 13 
               
               
                   
                 NCI-H460 
                 1,435 
                 9 
                 ND 
                 ND 
                 7 
               
               
                 Bone 
                 Saos-2 
                 3,281 
                 8 
                 2.925 
                 14.7 
                 23 
               
               
                 osteosarcoma 
                   
                   
                 9 
                 14.63 
                 73.2 
                 35 
               
               
                 Ewing 
                 A4573 
                 4,263 
                 8 
                 1.204 
                 6.1 
                 37 
               
               
                 sarcoma 
                   
                   
                 9 
                 9.705 
                 48.6 
                 33 
               
               
                   
               
            
           
         
       
     
     Collectively, the redirected T-cell killing of various target cell lines with anti-ROR1/anti-CD3 bispecific binding molecules with a range of properties and configurations identified certain trends. 
     Based on in vitro cytotoxicity assays using human PBMCs as effector cells and various target cell lines, configurations B, E and C tended to be more potent than configurations A and D. The relative potencies based on configurations may reflect the relative spatial positioning of the CD3 and ROR1 binding arms. The potency may also reflect the impact the various configurations have on trafficking of the bispecific binding molecules. For example, bispecific binding molecules of configurations B and C do not internalize as rapidly or to the same extent as bispecific binding molecules of configuration A. 
     Although the OKT3-based sequences appeared to have higher affinity for CD3 than the SP34-based sequences, bispecific binding molecules with bivalent SP34-based sequences were frequently more potent. The enhanced activity may reflect affinity, or, additionally or alternatively, the distinct epitope recognized by SP34. Interestingly, when bispecific binding molecules with monovalent CD3 binding were assessed, the trend was different. In some cases, the OKT3-based sequences were more potent than the SP34-based sequences ( FIG. 14 , compare constructs 13 and 15). 
     No direct correlation between target cell ROR expression levels and cytotoxicity was observed (Table 5). Nonetheless, the higher affinity variant of the anti-ROR antibody was more potent than the parental WT sequence. This may be of increased importance in situations where the ROR1 expression levels are lower. 
     The results of these experiments show that although the CD3 and ROR1 binding components can be optimized and characterized separately, the most active bispecific binding molecules can only be identified through empirical testing of different pairings of binding components using different bispecific configurations. The experiments demonstrate that constructs 9 and 18 (configuration B) were consistently among the most potent anti-ROR1/anti-CD3 bispecific binding molecules. This is particularly noteworthy as CD3 binding experiments demonstrated that these constructs were among the weakest binders to Jurkat cells in the absence of ROR1. This is expected to be a useful feature as activation and internalization of CD3 on T cells will be minimal until ROR1 is engaged in the tumor microenvironment. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Antigen-Binding Domains 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Schematic 
                 CD3 
                 Disulfide 
                 ROR1 
                 Knobs-into- 
               
               
                 Construct 
                 (FIG. 1) 
                 Antibody 
                 Stabilized 
                 Antibody 
                 Holes Variant 
               
               
                   
               
               
                  1 
                 A 
                 Ab8 
                 No 
                 Ab1 
                 No 
               
               
                  2 
                 A 
                 Ab9 
                 No 
                 Ab1 
                 No 
               
               
                  3 
                 A 
                 Ab10 
                 No 
                 Ab1 
                 No 
               
               
                  4 
                 A 
                 Ab8 
                 Yes 
                 Ab1 
                 No 
               
               
                  5 
                 A 
                 Ab9 
                 Yes 
                 Ab1 
                 No 
               
               
                  6 
                 A 
                 Ab10 
                 Yes 
                 Ab1 
                 No 
               
               
                  7 
                 B 
                 Ab8 
                 No 
                 Ab1 
                 No 
               
               
                  8 
                 B 
                 Ab9 
                 No 
                 Ab1 
                 No 
               
               
                  9 
                 B 
                 Ab10 
                 No 
                 Ab1 
                 No 
               
               
                 10 
                 B 
                 Ab8 
                 Yes 
                 Ab1 
                 No 
               
               
                 11 
                 B 
                 Ab9 
                 Yes 
                 Ab1 
                 No 
               
               
                 12 
                 B 
                 Ab10 
                 Yes 
                 Ab1 
                 No 
               
               
                 13 
                 C 
                 Ab8 
                 No 
                 Ab1 
                 Yes 
               
               
                 14 
                 C 
                 Ab9 
                 No 
                 Ab1 
                 Yes 
               
               
                 15 
                 C 
                 Ab10 
                 No 
                 Ab1 
                 Yes 
               
               
                 16 
                 C 
                 Ab10 
                 No 
                 Ab2 
                 Yes 
               
               
                 17 
                 C 
                 Ab10 
                 Yes 
                 Ab2 
                 Yes 
               
               
                 18 
                 B 
                 Ab10 
                 No 
                 Ab2 
                 No 
               
               
                 19 
                 D 
                 Ab10 
                 No 
                 Ab2 
                 Yes 
               
               
                 20 
                 E 
                 Ab10 
                 No 
                 Ab2 
                 No