Patent Publication Number: US-2021189391-A1

Title: PROGRAMMED CELL DEATH 1 LIGAND 1 (PD-L1) iRNA COMPOSITIONS AND METHODS OF USE THEREOF

Description:
RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 15/756,949, filed Mar. 1, 2018, now U.S. Pat. No. 10,889,813, issued Jan. 12, 2021, which is a 35 U.S.C. § 371 application entitled to the right of priority of International Application No. PCT/US2016/047946, filed Aug. 22, 2016, which claims the benefit of priority to U.S. Provisional Patent Application No. 62/213,224, filed on Sep. 2, 2015, the entire contents of which are hereby incorporated herein by reference. 
    
    
     STATEMENT REGARDING SEQUENCE LISTING 
     The Sequence Listing associated with this application is provided in text format in lieu of a paper copy, and is hereby incorporated by reference into the specification. The name of the text file containing the Sequence Listing is 930385_402 D1_SEQUENCE_LISTING. The text file is 105 KB, was created on Nov. 5, 2020, and is being submitted electronically via EFS-Web. 
     BACKGROUND OF THE INVENTION 
     Programmed cell death 1 ligand 1 (PD-L1) is a 290 amino acid type I transmembrane protein encoded by the CD274 gene on mouse chromosome 19 and human chromosome 9. PD-L1 expression is involved in evasion of immune responses involved in chronic infection, e.g., chronic viral infection (including, for example, HIV, HBV, HCV and HTLV, among others), chronic bacterial infection (including, for example,  Helicobacter pylori , among others), and chronic parasitic infection (including, for example,  Schistosoma mansoni ). PD-L1 expression has been detected in a number of tissues and cell types including T-cells, B-cells, macrophages, dendritic cells, and nonhematopoietic cells including endothelial cells, hepatocytes, muscle cells, and placenta. 
     PD-L1 expression is also involved in suppression of anti-tumor immune activity. Tumors express antigens that can be recognized by host T cells, but immunologic clearance of tumors is rare. Part of this failure is due to immune suppression by the tumor microenvironment. PD-L1 expression on many tumors is a component of this suppressive milieu and acts in concert with other immunosuppressive signals. PD-L1 expression has been shown in situ on a wide variety of solid tumors including breast, lung, colon, ovarian, melanoma, bladder, liver, salivary, stomach, gliomas, thyroid, thymic epithelial, head, and neck (Brown J A et al., 2003.  J. Immunol.  170:1257-66; Dong H et al. 2002 . Nat. Med.  8:793-800; Hamanishi J, et al. 2007 . Proc. Natl. Acad. Sci. USA  104:3360-65; Strome S E et al. 2003 . Cancer Res.  63:6501-5; Inman B A et al. 2007 . Cancer  109:1499-505; Konishi J et al. 2004 . Clin. Cancer Res.  10:5094-100; Nakanishi J et al. 2007 . Cancer Immunol. Immunother.  56:1173-82; Nomi T et al. 2007 . Clin. Cancer Res.  13:2151-57; Thompson R H et al. 2004 . Proc. Natl. Acad. Sci. USA  101:17174-79; Wu C, Zhu Y, Jiang J, Zhao J, Zhang X G, Xu N. 2006 . Acta Histochem.  108:19-24). In addition, the expression of the receptor for PD-L1, Programmed cell death protein 1 (also known as PD-1 and CD279) is upregulated on tumor infiltrating lymphocytes, and this also contributes to tumor immunosuppression (Blank C et al. 2003.  J. Immunol.  171:4574-81). Most importantly, studies relating PD-L1 expression on tumors to disease outcome show that PD-L1 expression strongly correlates with unfavorable prognosis in kidney, ovarian, bladder, breast, gastric, and pancreatic cancer (Hamanishi J et al. 2007 . Proc. Natl. Acad. Sci. USA  104:3360-65; Inman B A et al. 2007 . Cancer  109:1499-505; Konishi J et al. 2004 . Clin. Cancer Res.  10:5094-100; Nakanishi J et al. 2007 . Cancer Immunol. Immunother.  56:1173-82; Nomi T et al. 2007 . Clin. Cancer Res.  13:2151-57; Thompson R H et al. 2004 . Proc. Natl. Acad. Sci. USA  101:17174-79; Wu C, Zhu Y, Jiang J, Zhao J, Zhang X G, Xu N. 2006 . Acta Histochem.  108:19-24). In addition, these studies suggest that higher levels of PD-L1 expression on tumors may facilitate advancement of tumor stage and invasion into deeper tissue structures. 
     The PD-1 pathway can also play a role in hematologic malignancies. PD-L1 is expressed on multiple myeloma cells but not on normal plasma cells (Liu J et al. 2007 . Blood  110:296-304). PD-L1 is expressed on some primary T cell lymphomas, particularly anaplastic large cell T lymphomas (Brown J A et al., 2003 . J Immunol.  170:1257-66). PD-1 is highly expressed on the T cells of angioimmunoblastic lymphomas, and PD-L1 is expressed on the associated follicular dendritic cell network (Dorfman D M et al. 2006 . Am. J. Surg. Pathol.  30:802-10). In nodular lymphocyte-predominant Hodgkin lymphoma, the T cells associated with lymphocytic or histiocytic (L&amp;H) cells express PD-1. Microarray analysis using a readout of genes induced by PD-1 ligation suggests that tumor-associated T cells are responding to PD-1 signals in situ in Hodgkin lymphoma (Chemnitz J M et al. 2007 . Blood  110:3226-33). PD-1 and PD-L1 are expressed on CD4 T cells in HTLV-1-mediated adult T cell leukemia and lymphoma (Shimauchi T et al. 2007 . Int. J. Cancer  121: 2585-90). These tumor cells are hyporesponsive to TCR signals. 
     Studies in animal models demonstrate that PD-L1 on tumors inhibits T cell activation and lysis of tumor cells and in some cases leads to increased tumor-specific T cell death (Dong H et al. 2002 . Nat. Med.  8:793-800; Hirano F et al. 2005 . Cancer Res.  65:1089-96). Tumor-associated APCs can also utilize the PD-1:PD-L pathway to control antitumor T cell responses. PD-L1 expression on a population of tumor-associated myeloid DCs is upregulated by tumor environmental factors (Curiel T J et al. 2003 . Nat. Med.  9:562-67). Plasmacytoid dendritic cells (DCs) in the tumor-draining lymph node of B16 melanoma express IDO, which strongly activates the suppressive activity of regulatory T cells. The suppressive activity of IDO-treated regulatory T cells required cell contact with IDO-expressing DCs (Sharma M D et al. 2007.  J. Clin. Invest.  117:2570-82). 
     Accordingly, there is a need in the art for effective treatments for PD-L1-associated diseases, such as an infectious disease, such as a chronic intracellular infectious disease, e.g., a viral disease, e.g., hepatitis infection, or a bacterial infection, e.g., tuberculosis infection; and cancer, e.g., a hepatic cancer, e.g., hepatocellular carcinoma. 
     SUMMARY OF THE INVENTION 
     The present invention provides iRNA compositions which affect the RNA-induced silencing complex (RISC)-mediated cleavage of RNA transcripts of a PD-L1 gene. The PD-L1 gene may be within a cell, e.g., a cell within a subject, such as a human. 
     Accordingly, in one aspect, the invention provides a double stranded ribonucleic acid (RNAi) agent for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the RNAi comprises a sense strand and an antisense strand, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:2. 
     In certain embodiments, the sense strands and antisense strands comprise sequences selected from any of the sequences in Table 3. In other embodiments, the sense strands and antisense strands comprise sequences selected from any of the sequences in Table 5. 
     In an aspect, the invention provides a double stranded ribonucleic acid (dsRNA) agent for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the RNAi comprises a sense strand and an antisense strand, the antisense strand comprising a region of complementarity which comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of the antisense sequences listed in Table 3. In certain embodiments, the sense strands and antisense strands comprise sequences selected from any of the sequences in Table. 5 
     In certain embodiments, the RNAi comprises at least one modified nucleotide. In some embodiments, substantially all of the nucleotides of the sense strand and all of the nucleotides of the antisense strand comprise a modification. In some embodiments, all of the nucleotides of the sense strand and all of the nucleotides of the antisense strand comprise a modification. 
     In one aspect, the present invention provides double stranded ribonucleic acid (RNAi) agents for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the RNAi agents comprise a sense strand and an antisense strand, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of nucleotides 3221-3243, 351-372, 618-641, 618-639, 619-640, 620-641, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary portion of the nucleotide sequence of SEQ ID NO:2, and wherein the RNAi agent comprises at least one modified nucleotide. 
     In another aspect, the present invention provides double stranded ribonucleic acid (RNAi) agents for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the RNAi agents comprise a sense strand and an antisense strand, the antisense strand comprising a region of complementarity which comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of the antisense sequences in any one of the duplexes AD-67635, AD-67637, AD-67658, AD-67632, AD-67629, AD-67631, AD-67633, AD-67643, AD-67653, AD-67640, AD-67650, AD-67676, AD-67661, AD-67667, AD-67655, AD-67672, AD-67659, AD-67673, AD-67664, AD-67662, AD-67660, AD-67656, AD-67628, AD-67647, AD-67626, or AD-67645. 
     In one embodiment, the sense and antisense strands comprise nucleotide sequences selected from the group consisting of any one of the nucleotide sequences in any one of the duplexes AD-67635, AD-67637, AD-67658, AD-67632, AD-67629, AD-67631, AD-67633, AD-67643, AD-67653, AD-67640, AD-67650, AD-67676, AD-67661, AD-67667, AD-67655, AD-67672, AD-67659, AD-67673, AD-67664, AD-67662, AD-67660, AD-67656, AD-67628, AD-67647, AD-67626, or AD-67645. 
     In one aspect, the invention provides a double stranded RNAi agent for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the double stranded RNAi agent comprises a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:2, wherein substantially all of the nucleotides of the sense strand and substantially all of the nucleotides of the antisense strand are modified nucleotides, and wherein the sense strand is conjugated to a ligand attached at the 3′-terminus. 
     In one aspect, the present invention provides double stranded RNAi agents for inhibiting expression of PD-L1, which comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from nucleotides 3221-3243, 351-372, 618-641, 618-639, 619-640, 620-641, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides differing by no more than 3 nucleotides in the sense strand. 
     In certain embodiments, the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from nucleotides 3221-3243, 351-372, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides differing by no more than 3 nucleotides in the sense strand. 
     In certain embodiments, the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from nucleotides 3221-3243, 1093-1115, 1093-1114, 1094-1115, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides differing by no more than 3 nucleotides in the sense strand. 
     In another aspect, the present invention provides double stranded ribonucleic acid (RNAi) agents for inhibiting expression of programmed cell death 1 ligand 1 (PD-L1), wherein the double stranded RNAi agents comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of nucleotides 3221-3243, 351-372, 618-641, 618-639, 619-640, 620-641, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and said antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary portion of the nucleotide sequence of SEQ ID NO:2, wherein substantially all of the nucleotides of said sense strand and substantially all of the nucleotides of said antisense strand comprise nucleotide modifications, and wherein the sense strand is conjugated to a ligand attached at the 3′-terminus. 
     In certain embodiments, substantially all of the nucleotides of the sense strand or substantially all of the nucleotides of the antisense strand are modified nucleotides, or substantially all of the nucleotides of both strands are modified; and wherein the sense strand is conjugated to a ligand attached at the 3′-terminus. 
     In one aspect, the present invention provides double stranded RNAi agents for inhibiting expression of PD-L1, which comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides from nucleotides 3221-3243, 351-372, 618-641, 618-639, 619-640, 620-641, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides in the sense strand. 
     In certain embodiments, the agents comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides from nucleotides 3221-3243, 351-372, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides in the sense strand. 
     In certain embodiments, the agents comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides from nucleotides 3222-3243 1093-1115, 1093-1114, 1094-1115, 3221-3243, or 3221-3242, of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides from the complementary corresponding position of the nucleotide sequence of SEQ ID NO:2 such that the antisense strand is complementary to the at least 15 contiguous nucleotides in the sense strand. In certain embodiments, substantially all of the nucleotides of the sense strand are modified nucleotides. In certain embodiments, substantially all of the nucleotides of the antisense strand are modified nucleotides. In certain embodiments, substantially all of the nucleotides of both strands are modified. In preferred embodiments, the sense strand is conjugated to a ligand attached at the 3′-terminus. 
     In certain embodiments, the sense strand and the antisense strand comprise a region of complementarity which comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of the antisense sequences listed in any one of Tables 3 and 5. For example, in certain embodiment, the sense strand and the antisense strand comprise a region of complementarity which comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from any one of the antisense sequences of the duplexes AD-67635, AD-67637, AD-67658, AD-67632, AD-67629, AD-67631, AD-67633, AD-67643, AD-67653, AD-67640, AD-67650, AD-67676, AD-67661, AD-67667, AD-67655, AD-67672, AD-67659, AD-67673, AD-67664, AD-67662, AD-67660, AD-67656, AD-67628, AD-67647, AD-67626, or AD-67645. In certain embodiments, the sense strand and the antisense strand comprise a region of complementarity which comprises at least 15 contiguous nucleotides of any one of the antisense sequences of the foregoing duplexes. 
     In some embodiments, all of the nucleotides of the sense strand and all of the nucleotides of the antisense strand comprise a modification. In one embodiment, at least one of the modified nucleotides is selected from the group consisting of a deoxy-nucleotide, a 3′-terminal deoxy-thymine (dT) nucleotide, a 2′-O-methyl modified nucleotide, a 2′-fluoro modified nucleotide, a 2′-deoxy-modified nucleotide, a locked nucleotide, an unlocked nucleotide, a conformationally restricted nucleotide, a constrained ethyl nucleotide, an abasic nucleotide, a 2′-amino-modified nucleotide, a 2′-O-allyl-modified nucleotide, 2′-C-alkyl-modified nucleotide, 2′-hydroxyl-modified nucleotide, a 2′-methoxyethyl modified nucleotide, a 2′-O-alkyl-modified nucleotide, a morpholino nucleotide, a phosphoramidate, a non-natural base comprising nucleotide, a tetrahydropyran modified nucleotide, a 1,5-anhydrohexitol modified nucleotide, a cyclohexenyl modified nucleotide, a nucleotide comprising a phosphorothioate group, a nucleotide comprising a methylphosphonate group, a nucleotide comprising a 5′-phosphate, and a nucleotide comprising a 5′-phosphate mimic. In another embodiment, the modified nucleotides comprise a short sequence of 3′-terminal deoxy-thymine nucleotides (dT). 
     In certain embodiments, substantially all of the nucleotides of the sense strand are modified. In certain embodiments, substantially all of the nucleotides of the antisense strand are modified. In certain embodiments, substantially all of the nucleotides of both the sense strand and the antisense strand are modified. 
     In certain embodiments, the duplex comprises a modified antisense strand provided in Table 5. In certain embodiments, the duplex comprises a modified sense strand provided in Table 5. In certain embodiments, the duplex comprises a modified duplex provided in Table 5. 
     In certain embodiments, the region of complementarity between the antisense strand and the target is at least 17 nucleotides in length. For example, the region of complementarity between the antisense strand and the target is 19 to 21 nucleotides in length, for example, the region of complementarity is 21 nucleotides in length. In preferred embodiments, each strand is no more than 30 nucleotides in length. 
     In some embodiments, at least one strand comprises a 3′ overhang of at least 1 nucleotide, e.g., at least one strand comprises a 3′ overhang of at least 2 nucleotides. 
     In many embodiments, the RNAi agent further comprises a ligand. The ligand can be conjugated to the 3′ end of the sense strand of the RNAi agent. The ligand can be an N-acetylgalactosamine (GalNAc) derivative including, but not limited to 
     
       
         
         
             
             
         
       
     
     An exemplary RNAi agent conjugated to the ligand as shown in the following schematic: 
     
       
         
         
             
             
         
       
     
     and, wherein X is O or S. In one embodiment, the X is O. 
     In certain embodiments, the ligand can be a cholesterol moiety. 
     In certain embodiments, the region of complementarity comprises one of the antisense sequences of any one of Table 3 and Table 5. In another embodiment, the region of complementarity consists of one of the antisense sequences of any one of Table 3 and Table 5. 
     In another aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein: i, j, k, and l are each independently 0 or 1; p, p′, q, and q′ are each independently 0-6; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 nucleotides which are either modified or unmodified or combinations thereof; each n p , n o ′, n q , and n q ′, each of which may or may not be present, independently represents an overhang nucleotide; XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides; modifications on N b  differ from the modification on Y and modifications on N b ′ differ from the modification on Y′; and wherein the sense strand is conjugated to at least one ligand. 
     In certain embodiments, i is 0; j is 0; i is 1; j is 1; both i and j are 0; or both i and j are 1. In another embodiment, k is 0; 1 is 0; k is 1; l is 1; both k and l are 0; or both k and l are 1. In another embodiment, XXX is complementary to X′X′X′, YYY is complementary to Y′Y′Y′, and ZZZ is complementary to Z′Z′Z′. In another embodiment, the YYY motif occurs at or near the cleavage site of the sense strand. In another embodiment, the Y′Y′Y′ motif occurs at the 11, 12 and 13 positions of the antisense strand from the 5′-end. In one embodiment, the Y′ is 2′-O-methyl. 
     For example, formula (III) can be represented by formula (IIIa): 
       sense: 5′ n   p -N a -YYY-N a - n   q 3′
 
       antisense: 3′ n   p′ -N a′ -Y′Y′Y′-N a′ - n   q′ 5′  (IIIa).
 
     In another embodiment, formula (III) is represented by formula (IIIb): 
       sense: 5′ n   p -N a -YYY-N b -ZZZ-N a - n   q 3′
 
       antisense: 3′ n   p′ -N a′ -Y′Y′Y′-N b′ -Z′Z′Z′-N a′ - n   q′ 5′  (IIIb)
 
     wherein each N b  and N b ′ independently represents an oligonucleotide sequence comprising 1-5 modified nucleotides. 
     Alternatively, formula (III) can be represented by formula (IIIc): 
       sense: 5′ n   p -N a -XXX-N b -YYY-N a - n   q 3′
 
       antisense: antisense: 3′ n   p′ -N a′ -X′X′X′-N b′ -Y′Y′Y′-N a′ - n   q′ 5′  (IIIc)
 
     wherein each N b  and N b ′ independently represents an oligonucleotide sequence comprising 1-5 modified nucleotides. 
     Further, formula (III) can be represented by formula (IIId): 
       sense: 5′ n   p -N a -XXX-N b -YYY-N b -ZZZ-N a - n   q 3′
 
       antisense: 3′ n   p′ -N a′ -X′X′X′-N b′ -Y′Y′Y′-N b′ -Z′Z′Z′-N a′ - n   q′ 5′  (IIId)
 
     wherein each N b  and N b ′ independently represents an oligonucleotide sequence comprising 1-5 modified nucleotides and each N a  and N a ′ independently represents an oligonucleotide sequence comprising 2-10 modified nucleotides. 
     In certain embodiment, the double stranded region is 15-30 nucleotide pairs in length. For example, the double stranded region can be 17-23 nucleotide pairs in length. The double stranded region can be 17-25 nucleotide pairs in length. The double stranded region can be 23-27 nucleotide pairs in length. The double stranded region can be 19-21 nucleotide pairs in length. The double stranded region can be 21-23 nucleotide pairs in length. 
     In certain embodiments, each strand has 15-30 nucleotides. In other embodiments, each strand has 19-30 nucleotides. 
     Modifications on the nucleotides may be selected from the group including, but not limited to, LNA, HNA, CeNA, 2′-methoxyethyl, 2′-O-alkyl, 2′-O-allyl, 2′-C-allyl, 2′-fluoro, 2′-deoxy, 2′-hydroxyl, and combinations thereof. In another embodiment, the modifications on the nucleotides are 2′-O-methyl or 2′-fluoro modifications. 
     In certain embodiments, the ligand is one or more GalNAc derivatives attached through a monovalent linker or a bivalent or trivalent branched linker. In one embodiment, the ligand is 
     
       
         
         
             
             
         
       
     
     The ligand can be attached to the 3′ end of the sense strand. 
     An exemplary structure of a RNAi agent conjugated to the ligand is shown in the following schematic 
     
       
         
         
             
             
         
       
     
     In certain embodiments, the ligand can be a cholesterol moiety. 
     In certain embodiments, the RNAi agent further comprises at least one phosphorothioate or methylphosphonate internucleotide linkage. For example the phosphorothioate or methylphosphonate internucleotide linkage can be at the 3′-terminus of one strand, i.e., the sense strand or the antisense strand; or at the ends of both strands, the sense strand and the antisense strand. 
     In certain embodiments, the phosphorothioate or methylphosphonate internucleotide linkage is at the 5′-terminus of one strand, i.e., the sense strand or the antisense strand; or at the ends of both strands, the sense strand and the antisense strand. 
     In certain embodiments, the phosphorothioate or methylphosphonate internucleotide linkage is at the both the 5′- and 3′-terminus of one strand, i.e., the sense strand or the antisense strand; or at the ends of both strands, the sense strand and the antisense strand. 
     In certain embodiments, the base pair at the 1 position of the 5′-end of the antisense strand of the duplex is an AU base pair. 
     In certain embodiments, the Y nucleotides contain a 2′-fluoro modification. In another embodiment, the Y′ nucleotides contain a 2′-O-methyl modification. In another embodiment, p′&gt;0. In some embodiments, p′=2. In some embodiments, q′=0, p=0, q=0, and p′ overhang nucleotides are complementary to the target mRNA. In some embodiments, q′=0, p=0, q=0, and p′ overhang nucleotides are non-complementary to the target mRNA. 
     In certain embodiments, the sense strand has a total of 21 nucleotides and the antisense strand has a total of 23 nucleotides. 
     In certain embodiments, at least one n p ′ is linked to a neighboring nucleotide via a phosphorothioate linkage. In other embodiments, all n p ′ are linked to neighboring nucleotides via phosphorothioate linkages. 
     In certain embodiments, the RNAi agent is selected from the group of RNAi agents listed in any one of Tables 3 and 5. In certain embodiments, all of the nucleotides of the sense strand and all of the nucleotides of the antisense strand comprise a modification. 
     In one aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1 in a cell, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein i, j, k, and l are each independently 0 or 1; p, p′, q, and q′ are each independently 0-6; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 nucleotides which are either modified or unmodified or combinations thereof; each n p , n p ′, n q , and n q ′, each of which may or may not be present independently represents an overhang nucleotide; XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides, and wherein the modifications are 2′-O-methyl or 2′-fluoro modifications; modifications on N b  differ from the modification on Y and modifications on N b ′ differ from the modification on Y′; and wherein the sense strand is conjugated to at least one ligand. 
     In one aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1 in a cell, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein: i, j, k, and l are each independently 0 or 1; each n p , n q , and n q ′, each of which may or may not be present, independently represents an overhang nucleotide; 
     p, q, and q′ are each independently 0-6; n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via a phosphorothioate linkage; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 nucleotides which are either modified or unmodified or combinations thereof; XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides, and wherein the modifications are 2′-O-methyl or 2′-fluoro modifications; modifications on N b  differ from the modification on Y and modifications on N b ′ differ from the modification on Y′; and wherein the sense strand is conjugated to at least one ligand. 
     In one aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1 in a cell, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein i, j, k, and l are each independently 0 or 1; each n p , n q , and n q ′, each of which may or may not be present, independently represents an overhang nucleotide; p, q, and q′ are each independently 0-6; n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via a phosphorothioate linkage; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 nucleotides which are either modified or unmodified or combinations thereof; XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides, and wherein the modifications are 2′-O-methyl or 2′-fluoro modifications; modifications on N b  differ from the modification on Y and modifications on N b ′ differ from the modification on Y′; and wherein the sense strand is conjugated to at least one ligand, wherein the ligand is one or more GalNAc derivatives attached through a monovalent linker or a bivalent or trivalent branched linker. 
     In one aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1 in a cell, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein i, j, k, and l are each independently 0 or 1; each n p , n q , and n q ′, each of which may or may not be present, independently represents an overhang nucleotide; p, q, and q′ are each independently 0-6; n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via a phosphorothioate linkage; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 nucleotides which are either modified or unmodified or combinations thereof; XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides, and wherein the modifications are 2′-O-methyl or 2′-fluoro modifications; modifications on N b  differ from the modification on Y and modifications on N b ′ differ from the modification on Y′; wherein the sense strand comprises at least one phosphorothioate linkage; and wherein the sense strand is conjugated to at least one ligand, wherein the ligand is one or more GalNAc derivatives attached through a monovalent linker or a bivalent or trivalent branched linker. 
     In one aspect, the invention provides a double stranded RNAi agent capable of inhibiting the expression of PD-L1 in a cell, wherein the double stranded RNAi agent comprises a sense strand complementary to an antisense strand, wherein the antisense strand comprises a region complementary to part of an mRNA encoding PD-L1, wherein each strand is about 14 to about 30 nucleotides in length, wherein the double stranded RNAi agent is represented by formula (III): 
       sense: 5′ n   p -N a -YYY-N a - n   q 3′
 
       antisense:3′ n   p ′-N a ′-Y′Y′Y′-N a ′- n   q ′5′  (IIIa)
 
     wherein each n p , n q , and n q ′, each of which may or may not be present, independently represents an overhang nucleotide; p, q, and q′ are each independently 0-6; n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via a phosphorothioate linkage; each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 nucleotides which are either modified or unmodified or combinations thereof, each sequence comprising at least two differently modified nucleotides; YYY and Y′Y′Y′ each independently represent one motif of three identical modifications on three consecutive nucleotides, and wherein the modifications are 2′-O-methyl or 2′-fluoro modifications; wherein the sense strand comprises at least one phosphorothioate linkage; and wherein the sense strand is conjugated to at least one ligand, wherein the ligand is one or more GalNAc derivatives attached through a monovalent linker or a bivalent or trivalent branched linker. 
     In one aspect, the invention provides a double stranded RNAi agent for inhibiting expression of PD-L1, wherein the double stranded RNAi agent comprises a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the nucleotide sequence of SEQ ID NO:2, wherein substantially all of the nucleotides of the sense strand comprise a modification selected from a 2′-O-methyl modification and a 2′-fluoro modification, wherein the sense strand comprises two phosphorothioate internucleotide linkages at the 5′-terminus, wherein substantially all of the nucleotides of the antisense strand comprise a modification selected from a 2′-O-methyl modification and a 2′-fluoro modification, wherein the antisense strand comprises two phosphorothioate internucleotide linkages at the 5′-terminus and two phosphorothioate internucleotide linkages at the 3′-terminus, and wherein the sense strand is conjugated to one or more GalNAc derivatives attached through a monovalent linker or a branched bivalent or trivalent linker at the 3′-terminus. 
     In another aspect, the present invention provides double stranded ribonucleic acid (RNAi) agents for inhibiting expression of PD-L1, wherein the double stranded RNAi agents comprise a sense strand and an antisense strand forming a double stranded region, wherein the sense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from nucleotides 3221-3243, 351-372, 618-641, 618-639, 619-640, 620-641, 1093-1115, 1093-1114, 1094-1115, 1167-1188, 1293-1314, 1518-1539, 2103-2124, 2220-2261, 2220-2241, 2240-2261, 2648-2680, 2648-2669, 2658-2679, 2659-2680, 3143-3164, 3198-3219, 3221-3242, or 3222-3243 of the nucleotide sequence of SEQ ID NO:1 and the antisense strand comprises at least 15 contiguous nucleotides differing by no more than 3 nucleotides from the complementary portion of the nucleotide sequence of SEQ ID NO:2, wherein substantially all of the nucleotides of the sense strand comprise a nucleotide modification selected from the group consisting of a 2′-O-methyl modification and a 2′-fluoro modification, wherein the sense strand comprises two phosphorothioate internucleotide linkages at the 5′-terminus, wherein substantially all of the nucleotides of the antisense strand comprise a nucleotide modification selected from the group consisting of a 2′-O-methyl modification and a 2′-fluoro modification, wherein the antisense strand comprises two phosphorothioate internucleotide linkages at the 5′-terminus and two phosphorothioate internucleotide linkages at the 3′-terminus, and wherein the sense strand is conjugated to one or more GalNAc derivatives attached through a branched bivalent or trivalent linker at the 3′-terminus. 
     In certain embodiments, all of the nucleotides of the sense strand and all of the nucleotides of the antisense strand are modified nucleotides. In certain embodiments, each strand has 19-30 nucleotides. 
     In certain embodiments, substantially all of the nucleotides of the sense strand are modified. In certain embodiments, substantially all of the nucleotides of the antisense strand are modified. In certain embodiments, substantially all of the nucleotides of both the sense strand and the antisense strand are modified. 
     In one aspect, the invention provides a cell containing the RNAi agent as described herein. 
     In one aspect, the invention provides a vector encoding at least one strand of a RNAi agent, wherein the RNAi agent comprises a region of complementarity to at least a part of an mRNA encoding PD-L1, wherein the RNAi is 30 base pairs or less in length, and wherein the RNAi agent targets the mRNA for cleavage. In certain embodiments, the region of complementarity is at least 15 nucleotides in length. In certain embodiments, the region of complementarity is 19 to 23 nucleotides in length. 
     In one aspect, the invention provides a cell comprising a vector as described herein. 
     In one aspect, the invention provides a pharmaceutical composition for inhibiting expression of a PD-L1 gene comprising the RNAi agent of the invention. In one embodiment, the RNAii agent is administered in an unbuffered solution. In certain embodiments, the unbuffered solution is saline or water. In other embodiments, the RNAii agent is administered in a buffered solution. In such embodiments, the buffer solution can comprise acetate, citrate, prolamine, carbonate, or phosphate, or any combination thereof. For example, the buffer solution can be phosphate buffered saline (PBS). 
     In one aspect, the invention provides a pharmaceutical composition comprising the double stranded RNAi agent of the invention and a lipid formulation. In certain embodiments, the lipid formulation comprises a LNP. In certain embodiments, the lipid formulation comprises an MC3. 
     In one aspect, the invention provides a method of inhibiting PD-L1 expression in a cell, the method comprising (a) contacting the cell with the double stranded RNAi agent of the invention or a pharmaceutical composition of the invention; and (b) maintaining the cell produced in step (a) for a time sufficient to obtain degradation of the mRNA transcript of a PD-L1 gene, thereby inhibiting expression of the PD-L1 gene in the cell. In certain embodiments, the cell is within a subject, for example, a human subject, for example a female human or a male human. In preferred embodiments, PD-L1 expression is inhibited by at least 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%, or to below the threshold of detection of the assay method used. 
     In one aspect, the invention provides a method of treating a subject having a disease or disorder that would benefit from reduction in PD-L1 expression, the method comprising administering to the subject a therapeutically effective amount of the RNAi agent of the invention or a pharmaceutical composition of the invention, thereby treating the subject. 
     In one aspect, the invention provides a method of preventing at least one symptom in a subject having a disease or disorder that would benefit from reduction in PD-L1 expression, the method comprising administering to the subject a prophylactically effective amount of the RNAi agent of the invention or a pharmaceutical composition of the invention, thereby preventing at least one symptom in the subject having a disorder that would benefit from reduction in PD-L1 expression. 
     In certain embodiments, the administration of the RNAi to the subject causes a decrease in the PD-L1 signaling pathway. In certain embodiments, the administration of the RNAi causes a decrease in the level of PD-L1 in the subject, e.g., serum levels of PD-L1 in the subject. 
     In certain embodiments, the PD-L1-associated disease is an infectious disease, such as a chronic, intracellular infectious disease, e.g., a viral disease, e.g., hepatitis infection, or a bacterial infection, e.g., tuberculosis infection. 
     In certain embodiments, the PD-L1-associated disease is cancer, e.g., a hepatic cancer, e.g., hepatocellular carcinoma. 
     In certain embodiments, the invention further comprises administering an anti-viral agent to a subject with a PD-L1-associated disease. In certain embodiments, the anti-viral agent is a nucleotide or nucleoside analog. In certain embodiments, the anti-viral agent is for treatment of a hepatitis virus infection, e.g., an HBV infection, an HDV infection. In certain embodiments, the anti-viral agent is not an immune stimulatory agent. 
     In certain embodiments, the invention further comprises administering a chemotherapeutic agent to a subject with a PD-L1-associated disease. 
     In certain embodiments wherein the PD-L1-associated disease is cancer, the subject is further treated for cancer. In certain embodiments, the treatment for cancer includes surgery. In certain embodiments, the treatment for cancer includes radiation. In certain embodiments, the treatment for cancer includes administration of a chemotherapeutic agent. 
     In various embodiments, the RNAi agent is administered at a dose of about 0.01 mg/kg to about 10 mg/kg or about 0.5 mg/kg to about 50 mg/kg. In some embodiments, the RNAi agent is administered at a dose of about 10 mg/kg to about 30 mg/kg. In certain embodiments, the RNAi agent is administered at a dose selected from about 0.5 mg/kg 1 mg/kg, 1.5 mg/kg, 3 mg/kg, 5 mg/kg, 10 mg/kg, and 30 mg/kg. In certain embodiments, the RNAi agent is administered about once per week, once per month, once every other two months, or once a quarter (i.e., once every three months) at a dose of about 0.1 mg/kg to about 5.0 mg/kg. 
     In certain embodiments, the RNAi agent is administered to the subject once a week. In certain embodiments, the RNAii agent is administered to the subject once a month. In certain embodiments, the RNAii agent is administered once per quarter (i.e., every three months). 
     In some embodiment, the RNAi agent is administered to the subject subcutaneously. 
     In various embodiments, the methods of the invention further comprise measuring PD-L1 levels in the subject. In certain embodiments, a decrease in the levels of expression or activity of the PD-L1 signaling pathway indicates that the PD-L1-associated disease is being treated. 
     In various embodiments, a surrogate marker of PD-L1 expression is measured. For example, in the treatment of infectious disease, the presence of the pathogen is detected, e.g., a protein or nucleic acid from the pathogen, e.g., HBsAg, HBeAg, HB cccDNA. In certain embodiments, an indicator of an immune response against the pathogen is detected, e.g., anti-HBs antibody. In certain embodiments, a change, preferably a clinically relevant change in the surrogate marker indicating effective treatment of the infection is detected. In the treatment of cancer, a demonstration of stabilization or reduction of tumor burden using RECIST criteria can be used as a surrogate marker for a reduction of PD-L1 expression or activity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic showing a PD-L1 signaling between an antigen presenting cell and a T-cell. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides iRNA compositions which effect the RNA-induced silencing complex (RISC)-mediated cleavage of RNA transcripts of an programmed cell death 1 ligand 1 (PD-L1) gene. The gene may be within a cell, e.g., a cell within a subject, such as a human. The use of these iRNAs enables the targeted degradation of mRNAs of the corresponding gene (PD-L1 gene) in mammals. 
     The iRNAs of the invention have been designed to target the human PD-L1 gene, including portions of the gene that are conserved in the PD-L1 orthologs of other mammalian species. Without intending to be limited by theory, it is believed that a combination or sub-combination of the foregoing properties and the specific target sites or the specific modifications in these iRNA agents confer to the iRNAs of the invention improved efficacy, stability, potency, durability, and safety. 
     Accordingly, the present invention also provides methods for treating a subject having a disorder that would benefit from inhibiting or reducing the expression of a PD-L1 gene, e.g., an PD-L1-associated disease, such as infection, e.g., a viral infection, e.g., a hepatitis virus infection, or cancer, such as a liver cancer, e.g., hepatic cellular carcinoma, using iRNA compositions which effect the RNA-induced silencing complex (RISC)-mediated cleavage of RNA transcripts of an PD-L1 gene. 
     Very low dosages of the iRNAs of the invention, in particular, can specifically and efficiently mediate RNA interference (RNAi), resulting in significant inhibition of expression of the corresponding gene (PD-L1 gene). 
     The iRNAs of the invention include an RNA strand (the antisense strand) having a region which is about 30 nucleotides or less in length, e.g., 15-30, 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 nucleotides in length, which region is substantially complementary to at least part of an mRNA transcript of a PD-L1 gene. In certain embodiments, the iRNAs of the invention include an RNA strand (the antisense strand) which can include longer lengths, for example up to 66 nucleotides, e.g., 36-66, 26-36, 25-36, 31-60, 22-43, 27-53 nucleotides in length with a region of at least 19 contiguous nucleotides that is substantially complementary to at least a part of an mRNA transcript of a PD-L1 gene. These iRNAs with the longer length antisense strands preferably include a second RNA strand (the sense strand) of 20-60 nucleotides in length wherein the sense and antisense strands form a duplex of 18-30 contiguous nucleotides. The use of these iRNAs enables the targeted degradation of mRNAs of the corresponding gene (PD-L1 gene) in mammals. Very low dosages of the iRNAs of the invention, in particular, can specifically and efficiently mediate RNA interference (RNAi), resulting in significant inhibition of expression of the corresponding gene (PD-L1 gene). Using in vitro and in vivo assays, the present inventors have demonstrated that iRNAs targeting a PD-L1 gene can mediate RNAi, resulting in significant inhibition of expression of PD-L1, as well as reducing signaling through the PD-L1 pathway which will decrease one or more of the symptoms associated with a PD-L1-associated disease, such as an infectious disease, e.g., a viral disease or chronic intracellular infection; or cancer. Thus, methods and compositions including these iRNAs are useful for treating a subject having a PD-L1-associated disease, such as an infectious disease, e.g., a viral disease or chronic intracellular infection, or cancer. The methods and compostions herein are useful for reducing the level of PD-L1 in a subject, e.g., liver PD-L1 in a subject, especially in a subject with a chronic intracellular infection, especially a chronic hepatic infection, or tumor. 
     The following detailed description discloses how to make and use compositions containing iRNAs to inhibit the expression of a PD-L1 gene as well as compositions, uses, and methods for treating subjects having diseases and disorders that would benefit from reduction of the expression of a PD-L1 gene. 
     I. Definitions 
     In order that the present invention may be more readily understood, certain terms are first defined. In addition, it should be noted that whenever a value or range of values of a parameter are recited, it is intended that values and ranges intermediate to the recited values are also intended to be part of this invention. 
     The articles “a” and “an” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element, e.g., a plurality of elements. 
     The term “including” is used herein to mean, and is used interchangeably with, the phrase “including but not limited to”. 
     The term “or” is used herein to mean, and is used interchangeably with, the term “and/or,” unless context clearly indicates otherwise. For example, “sense strand or antisense strand” is understood as “sense strand or antisense strand or sense strand and antisense strand.” 
     The term “about” is used herein to mean within the typical ranges of tolerances in the art. For example, “about” can be understood as about 2 standard deviations from the mean. In certain embodiments, about means±10%. In certain embodiments, about means±5%. When about is present before a series of numbers or a range, it is understood that “about” can modify each of the numbers in the series or range. 
     The term “at least” prior to a number or series of numbers is understood to include the number adjacent to the term “at least”, and all subsequent numbers or integers that could logically be included, as clear from context. For example, the number of nucleotides in a nucleic acid molecule must be an integer. For example, “at least 18 nucleotides of a 21 nucleotide nucleic acid molecule” means that 18, 19, 20, or 21 nucleotides have the indicated property. When at least is present before a series of numbers or a range, it is understood that “at least” can modify each of the numbers in the series or range. 
     As used herein, “no more than” or “less than” is understood as the value adjacent to the phrase and logical lower values or intergers, as logical from context, to zero. For example, a duplex with an overhang of “no more than 2 nucleotides” has a 2, 1, or 0 nucleotide overhang. When “no more than” is present before a series of numbers or a range, it is understood that “no more than” can modify each of the numbers in the series or range. 
     In the event of a conflict between a sequence and its indicated site on a transcript or other sequence, the nucleotide sequence recited in the specification takes precedence. 
     Various embodiments of the invention can be combined as determined appropriate by one of skill in the art. 
     “Programmed cell death 1 ligand 1”, “PD-L1”, or “CD274,” also known as B7-H; B7H1; PDL1; PD-L1; PDCD1L1; PDCD1LG1, B7 homolog 1, PDCD1 ligand 1, and programmed cell death ligand 1, has been shown to be constitutively expressed on mouse T and B cells, DCs, macrophages, mesenchymal stem cells, and bone marrow—derived mast cells. PD-L1 expression is also found on a wide range of nonhematopoietic cells and is upregulated on a number of cell types after activation. Upon IFN-γ stimulation, PD-L1 is expressed on T cells, NK cells, macrophages, myeloid DCs, B cells, epithelial cells, and vascular endothelial cells (Flies D B and Chen L (2007)  J Immunother.  30 (3): 251-60). PD-L1 is notably expressed on macrophages. Further information on PD-L1 is provided, for example in the NCBI Gene database at www.ncbi.nlm.nih.gov/gene/29126 (which is incorporated herein by reference as of the date of filing this application). 
     As used herein, “programmed cell death 1 ligand 1” is used interchangeably with the term “PD-L1” (and optionally any of the other recognized names listed above) refers to the naturally occurring gene that encodes a programmed cell death 1 ligand 1 protein. The amino acid and complete coding sequences of the reference sequence of the human PDL-1 gene may be found in, for example, GenBank Accession No. GI: 390979638 (RefSeq Accession No. NM_001267706.1; SEQ ID NO:1; SEQ ID NO:2) and GenBank Accession No. GI: 292658763 (RefSeq Accession No. NM_014143.3; SEQ ID NO: 9 and 10). Further splice variants are provided, for example, in Grzywnowicz et al.,  PLoS One.  2012; 7:e35178 which is incorporated herein by reference. Mammalian orthologs of the human PD-L1 gene may be found in, for example, GI: 755563510 (RefSeq Accession No. XM_006527249.2, mouse; SEQ ID NO:3 and SEQ ID NO:4); GI: 672040129 (RefSeq Accession No. XM_006231248.2, rat; SEQ ID NO:5 and SEQ ID NO:6); GenBank Accession Nos. GI: 544494555 (RefSeq Accession No. XM_005581779.1, cynomolgus monkey; SEQ ID NO:7 and SEQ ID NO:8). 
     A number of naturally occurring SNPs are known and can be found, for example, in the SNP database at the NCBI at www.ncbi.nlm.nih.gov/SNP/snp_refcgi?locusId=29126 (which is incorporated herein by reference as of the date of filing this application) which lists SNPs in human PD-L1. In preferred embodiments, such naturally occurring variants are included within the scope of the PD-L1 gene sequence. 
     Additional examples of PD-L1 mRNA sequences are readily available using publicly available databases, e.g., GenBank, UniProt, and OMIM. 
     As used herein, “target sequence” refers to a contiguous portion of the nucleotide sequence of an mRNA molecule formed during the transcription of a PD-L1 gene, including mRNA that is a product of RNA processing of a primary transcription product. The target portion of the sequence will be at least long enough to serve as a substrate for iRNA-directed cleavage at or near that portion of the nucleotide sequence of an mRNA molecule formed during the transcription of a PD-L1 gene. In one embodiment, the target sequence is within the protein coding region of PD-L1. 
     The target sequence may be from about 9-36 nucleotides in length, e.g., about 15-30 nucleotides in length. For example, the target sequence can be from about 15-30 nucleotides, 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 nucleotides in length. Ranges and lengths intermediate to the above recited ranges and lengths are also contemplated to be part of the invention. 
     As used herein, the term “strand comprising a sequence” refers to an oligonucleotide comprising a chain of nucleotides that is described by the sequence referred to using the standard nucleotide nomenclature. 
     “G,” “C,” “A,” “T,” and “U” each generally stand for a nucleotide that contains guanine, cytosine, adenine, thymidine, and uracil as a base, respectively. However, it will be understood that the term “ribonucleotide” or “nucleotide” can also refer to a modified nucleotide, as further detailed below, or a surrogate replacement moiety (see, e.g., Table 2). The skilled person is well aware that guanine, cytosine, adenine, and uracil can be replaced by other moieties without substantially altering the base pairing properties of an oligonucleotide comprising a nucleotide bearing such replacement moiety. For example, without limitation, a nucleotide comprising inosine as its base can base pair with nucleotides containing adenine, cytosine, or uracil. Hence, nucleotides containing uracil, guanine, or adenine can be replaced in the nucleotide sequences of dsRNA featured in the invention by a nucleotide containing, for example, inosine. In another example, adenine and cytosine anywhere in the oligonucleotide can be replaced with guanine and uracil, respectively to form G-U Wobble base pairing with the target mRNA. Sequences containing such replacement moieties are suitable for the compositions and methods featured in the invention. 
     The terms “iRNA”, “RNAi agent,” and “iRNA agent,” “RNA interference agent” as used interchangeably herein, refer to an agent that contains RNA as that term is defined herein, and which mediates the targeted cleavage of an RNA transcript via an RNA-induced silencing complex (RISC) pathway. iRNA directs the sequence-specific degradation of mRNA through a process known as RNA interference (RNAi). The iRNA modulates, e.g., inhibits, the expression of a PD-L1 gene in a cell, e.g., a cell within a subject, such as a mammalian subject. 
     In one embodiment, an RNAi agent of the invention includes a single stranded RNA that interacts with a target RNA sequence, e.g., a PD-L1 target mRNA sequence, to direct the cleavage of the target RNA. Without wishing to be bound by theory it is believed that long double stranded RNA introduced into cells is broken down into siRNA by a Type III endonuclease known as Dicer (Sharp et al. (2001)  Genes Dev.  15:485). Dicer, a ribonuclease-III-like enzyme, processes the dsRNA into 19-23 base pair short interfering RNAs with characteristic two base 3′ overhangs (Bernstein, et al., (2001)  Nature  409:363). The siRNAs are then incorporated into an RNA-induced silencing complex (RISC) where one or more helicases unwind the siRNA duplex, enabling the complementary antisense strand to guide target recognition (Nykanen, et al., (2001)  Cell  107:309). Upon binding to the appropriate target mRNA, one or more endonucleases within the RISC cleave the target to induce silencing (Elbashir, et al., (2001)  Genes Dev.  15:188). Thus, in one aspect the invention relates to a single stranded RNA (siRNA) generated within a cell and which promotes the formation of a RISC complex to effect silencing of the target gene, i.e., a PD-L1 gene. Accordingly, the term “siRNA” is also used herein to refer to an iRNA as described above. 
     In certain embodiments, the RNAi agent may be a single-stranded siRNA (ssRNAi) that is introduced into a cell or organism to inhibit a target mRNA. Single-stranded RNAi agents bind to the RISC endonuclease, Argonaute 2, which then cleaves the target mRNA. The single-stranded siRNAs are generally 15-30 nucleotides and are chemically modified. The design and testing of single-stranded siRNAs are described in U.S. Pat. No. 8,101,348 and in Lima et al., (2012)  Cell  150:883-894, the entire contents of each of which are hereby incorporated herein by reference. Any of the antisense nucleotide sequences described herein may be used as a single-stranded siRNA as described herein or as chemically modified by the methods described in Lima et al., (2012)  Cell  150:883-894. 
     In certain embodiments, an “iRNA” for use in the compositions, uses, and methods of the invention is a double stranded RNA and is referred to herein as a “double stranded RNAi agent,” “double stranded RNA (dsRNA) molecule,” “dsRNA agent,” or “dsRNA”. The term “dsRNA”, refers to a complex of ribonucleic acid molecules, having a duplex structure comprising two anti-parallel and substantially complementary nucleic acid strands, referred to as having “sense” and “antisense” orientations with respect to a target RNA, i.e., a PD-L1 gene. In some embodiments of the invention, a double stranded RNA (dsRNA) triggers the degradation of a target RNA, e.g., an mRNA, through a post-transcriptional gene-silencing mechanism referred to herein as RNA interference or RNAi. 
     In general, the majority of nucleotides of each strand of a dsRNA molecule are ribonucleotides, but as described in detail herein, each or both strands can also include one or more non-ribonucleotides, e.g., a deoxyribonucleotide or a modified nucleotide. In addition, as used in this specification, an “iRNA” may include ribonucleotides with chemical modifications; an iRNA may include substantial modifications at multiple nucleotides. As used herein, the term “modified nucleotide” refers to a nucleotide having, independently, a modified sugar moiety, a modified internucleotide linkage, or modified nucleobase, or any combination thereof. Thus, the term modified nucleotide encompasses substitutions, additions or removal of, e.g., a functional group or atom, to internucleoside linkages, sugar moieties, or nucleobases. The modifications suitable for use in the agents of the invention include all types of modifications disclosed herein or known in the art. Any such modifications, as used in a siRNA type molecule, are encompassed by “iRNA” or “RNAi agent” for the purposes of this specification and claims. 
     The duplex region may be of any length that permits specific degradation of a desired target RNA through a RISC pathway, and may range from about 9 to 36 base pairs in length, e.g., about 15-30 base pairs in length, for example, about 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36 base pairs in length, such as about 15-30, 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 base pairs in length. Ranges and lengths intermediate to the above recited ranges and lengths are also contemplated to be part of the invention. 
     The two strands forming the duplex structure may be different portions of one larger RNA molecule, or they may be separate RNA molecules. Where the two strands are part of one larger molecule, and therefore are connected by an uninterrupted chain of nucleotides between the 3′-end of one strand and the 5′-end of the respective other strand forming the duplex structure, the connecting RNA chain is referred to as a “hairpin loop.” A hairpin loop can comprise at least one unpaired nucleotide. In some embodiments, the hairpin loop can comprise at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 23 or more unpaired nucleotides. In some embodiments, the hairpin loop can be 10 or fewer nucleotides. In some embodiments, the hairpin loop can be 8 or fewer unpaired nucleotides. In some embodiments, the hairpin loop can be 4-10 unpaired nucleotides. In some embodiments, the hairpin loop can be 4-8 nucleotides. 
     Where the two substantially complementary strands of a dsRNA are comprised by separate RNA molecules, those molecules need not, but can be covalently connected. Where the two strands are connected covalently by means other than an uninterrupted chain of nucleotides between the 3′-end of one strand and the 5′-end of the respective other strand forming the duplex structure, the connecting structure is referred to as a “linker.” The RNA strands may have the same or a different number of nucleotides. The maximum number of base pairs is the number of nucleotides in the shortest strand of the dsRNA minus any overhangs that are present in the duplex. In addition to the duplex structure, an RNAi may comprise one or more nucleotide overhangs. 
     In certain embodiments, an iRNA agent of the invention is a dsRNA, each strand of which comprises 19-23 nucleotides, that interacts with a target RNA sequence, e.g., a PD-L1 gene, without wishing to be bound by theory, long double stranded RNA introduced into cells is broken down into siRNA by a Type III endonuclease known as Dicer (Sharp et al. (2001)  Genes Dev.  15:485). Dicer, a ribonuclease-III-like enzyme, processes the dsRNA into 19-23 base pair short interfering RNAs with characteristic two base 3′ overhangs (Bernstein, et al., (2001)  Nature  409:363). The siRNAs are then incorporated into an RNA-induced silencing complex (RISC) where one or more helicases unwind the siRNA duplex, enabling the complementary antisense strand to guide target recognition (Nykanen, et al., (2001)  Cell  107:309). Upon binding to the appropriate target mRNA, one or more endonucleases within the RISC cleave the target to induce silencing (Elbashir, et al., (2001)  Genes Dev.  15:188). 
     In some embodiments, an iRNA of the invention is a dsRNA of 24-30 nucleotides, or possibly even longer, e.g., 25-35, 27-53, or 27-49 nucleotides, that interacts with a target RNA sequence, e.g., a PD-L1 target mRNA sequence, to direct the cleavage of the target RNA. Without wishing to be bound by theory, long double stranded RNA introduced into cells is broken down into siRNA by a Type III endonuclease known as Dicer (Sharp et al. (2001)  Genes Dev.  15:485). Dicer, a ribonuclease-III-like enzyme, processes the dsRNA into 19-23 base pair short interfering RNAs with characteristic two base 3′ overhangs (Bernstein, et al., (2001)  Nature  409:363). The siRNAs are then incorporated into an RNA-induced silencing complex (RISC) where one or more helicases unwind the siRNA duplex, enabling the complementary antisense strand to guide target recognition (Nykanen, et al., (2001)  Cell  107:309). Upon binding to the appropriate target mRNA, one or more endonucleases within the RISC cleave the target to induce silencing (Elbashir, et al., (2001)  Genes Dev.  15:188). 
     As used herein, the term “nucleotide overhang” refers to at least one unpaired nucleotide that protrudes from the duplex structure of a double stranded iRNA. For example, when a 3′-end of one strand of a dsRNA extends beyond the 5′-end of the other strand, or vice versa, there is a nucleotide overhang. A dsRNA can comprise an overhang of at least one nucleotide; alternatively the overhang can comprise at least two nucleotides, at least three nucleotides, at least four nucleotides, at least five nucleotides or more. A nucleotide overhang can comprise or consist of a nucleotide/nucleoside analog, including a deoxynucleotide/nucleoside. The overhang(s) can be on the sense strand, the antisense strand, or any combination thereof. Furthermore, the nucleotide(s) of an overhang can be present on the 5′-end, 3′-end, or both ends of either an antisense or sense strand of a dsRNA. 
     In certain embodiments, the antisense strand of a dsRNA has a 1-10 nucleotide, e.g., 0-3, 1-3, 2-4, 2-5, 4-10, 5-10, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nucleotide, overhang at the 3′-end or the 5′-end. In certain embodiments, the overhang on the sense strand or the antisense strand, or both, can include extended lengths longer than 10 nucleotides, e.g., 1-30 nucleotides, 2-30 nucleotides, 10-30 nucleotides, or 10-15 nucleotides in length. In certain embodiments, an extended overhang is on the sense strand of the duplex. In certain embodiments, an extended overhang is present on the 3′end of the sense strand of the duplex. In certain embodiments, an extended overhang is present on the 5′end of the sense strand of the duplex. In certain embodiments, an extended overhang is on the antisense strand of the duplex. In certain embodiments, an extended overhang is present on the 3′end of the antisense strand of the duplex. In certain embodiments, an extended overhang is present on the 5′end of the antisense strand of the duplex. In certain embodiments, one or more of the nucleotides in the overhang is replaced with a nucleoside thiophosphate. 
     “Blunt” or “blunt end” means that there are no unpaired nucleotides at that end of the double stranded RNAi agent, i.e., no nucleotide overhang. A “blunt ended” double stranded RNAi agent is double stranded over its entire length, i.e., no nucleotide overhang at either end of the molecule. The RNAi agents of the invention include RNAi agents with no nucleotide overhang at one end (i.e., agents with one overhang and one blunt end) or with no nucleotide overhangs at either end. 
     The term “antisense strand” or “guide strand” refers to the strand of an iRNA, e.g., a dsRNA, which includes a region that is substantially complementary to a target sequence, e.g., a PD-L1 mRNA. As used herein, the term “region of complementarity” refers to the region on the antisense strand that is substantially complementary to a sequence, for example a target sequence, e.g., a PD-L1 nucleotide sequence, as defined herein. Where the region of complementarity is not fully complementary to the target sequence, the mismatches can be in the internal or terminal regions of the molecule. Generally, the most tolerated mismatches are in the terminal regions, e.g., within 5, 4, 3, 2, or 1 nucleotides of the 5′- or 3′-end of the iRNA. In some embodiments, a double stranded RNAi agent of the invention includes a nucleotide mismatch in the antisense strand. In some embodiments, a double stranded RNAi agent of the invention includes a nucleotide mismatch in the sense strand. In some embodiments, the nucleotide mismatch is, for example, within 5, 4, 3, 2, or 1 nucleotides from the 3′-end of the iRNA. In another embodiment, the nucleotide mismatch is, for example, in the 3′-terminal nucleotide of the iRNA. 
     The term “sense strand” or “passenger strand” as used herein, refers to the strand of an iRNA that includes a region that is substantially complementary to a region of the antisense strand as that term is defined herein. 
     As used herein, the term “cleavage region” refers to a region that is located immediately adjacent to the cleavage site. The cleavage site is the site on the target at which cleavage occurs. In some embodiments, the cleavage region comprises three bases on either end of, and immediately adjacent to, the cleavage site. In some embodiments, the cleavage region comprises two bases on either end of, and immediately adjacent to, the cleavage site. In some embodiments, the cleavage site specifically occurs at the site bound by nucleotides 10 and 11 of the antisense strand, and the cleavage region comprises nucleotides 11, 12 and 13. 
     As used herein, and unless otherwise indicated, the term “complementary,” when used to describe a first nucleotide sequence in relation to a second nucleotide sequence, refers to the ability of an oligonucleotide or polynucleotide comprising the first nucleotide sequence to hybridize and form a duplex structure under certain conditions with an oligonucleotide or polynucleotide comprising the second nucleotide sequence, as will be understood by the skilled person. Such conditions can, for example, be stringent conditions, where stringent conditions can include: 400 mM NaCl, 40 mM PIPES pH 6.4, 1 mM EDTA, 50° C. or 70° C. for 12-16 hours followed by washing (see, e.g., “ Molecular Cloning: A Laboratory Manual , Sambrook, et al. (1989) Cold Spring Harbor Laboratory Press). Other conditions, such as physiologically relevant conditions as can be encountered inside an organism, can apply. The skilled person will be able to determine the set of conditions most appropriate for a test of complementarity of two sequences in accordance with the ultimate application of the hybridized nucleotides. 
     Complementary sequences within an iRNA, e.g., within a dsRNA as described herein, include base-pairing of the oligonucleotide or polynucleotide comprising a first nucleotide sequence to an oligonucleotide or polynucleotide comprising a second nucleotide sequence over the entire length of one or both nucleotide sequences. Such sequences can be referred to as “fully complementary” with respect to each other herein. However, where a first sequence is referred to as “substantially complementary” with respect to a second sequence herein, the two sequences can be fully complementary, or they can form one or more, but generally not more than 5, 4, 3, or 2 mismatched base pairs upon hybridization for a duplex up to 30 base pairs, while retaining the ability to hybridize under the conditions most relevant to their ultimate application, e.g., inhibition of gene expression via a RISC pathway. However, where two oligonucleotides are designed to form, upon hybridization, one or more single stranded overhangs, such overhangs shall not be regarded as mismatches with regard to the determination of complementarity. For example, a dsRNA comprising one oligonucleotide 21 nucleotides in length and another oligonucleotide 23 nucleotides in length, wherein the longer oligonucleotide comprises a sequence of 21 nucleotides that is fully complementary to the shorter oligonucleotide, can yet be referred to as “fully complementary” for the purposes described herein. 
     “Complementary” sequences, as used herein, can also include, or be formed entirely from, non-Watson-Crick base pairs or base pairs formed from non-natural and modified nucleotides, in so far as the above requirements with respect to their ability to hybridize are fulfilled. Such non-Watson-Crick base pairs include, but are not limited to, G:U Wobble or Hoogstein base pairing. 
     The terms “complementary,” “fully complementary” and “substantially complementary” herein can be used with respect to the base matching between the sense strand and the antisense strand of a dsRNA, or between the antisense strand of a double stranded RNAi agent and a target sequence, as will be understood from the context of their use. 
     As used herein, a polynucleotide that is “substantially complementary to at least part of” a messenger RNA (mRNA) refers to a polynucleotide that is substantially complementary to a contiguous portion of the mRNA of interest (e.g., an mRNA encoding a PD-L1 gene). For example, a polynucleotide is complementary to at least a part of a PD-L1 mRNA if the sequence is substantially complementary to a non-interrupted portion of an mRNA encoding a PD-L1 gene. 
     Accordingly, in some embodiments, the sense strand polynucleotides and the antisense polynucleotides disclosed herein are fully complementary to the target PD-L1 sequence. 
     In other embodiments, the antisense polynucleotides disclosed herein are substantially complementary to the target PD-L1 sequence and comprise a contiguous nucleotide sequence which is at least about 80% complementary over its entire length to the equivalent region of the nucleotide sequence of any one of SEQ ID NO:1, or a fragment of any one of SEQ ID NO:1, such as at least about 85%, 86%, 87%, 88%, 89%, about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% complementary or 100% complementary. 
     In some embodiments, an iRNA of the invention includes a sense strand that is substantially complementary to an antisense polynucleotide which, in turn, is complementary to a target PD-L1 sequence and comprises a contiguous nucleotide sequence which is at least about 80% complementary over its entire length to the equivalent region of the nucleotide sequence of any one of the antisense strands in Table 3 or Table 5, or a fragment of any one of the antisense strands in Table 3 and Table 5, such as about 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% complementary, or 100% complementary. 
     In some embodiments, an iRNA of the invention includes an antisense strand that is substantially complementary to the target PD-L1 sequence and comprises a contiguous nucleotide sequence which is at least 80% complementary over its entire length to the equivalent region of the nucleotide sequence of any one of the isense strands in Table 3 or 5, or a fragment of any one of the sense strands in Table 3 and 5, such as about 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% complementary, or 100% complementary. 
     In an aspect of the invention, an agent for use in the methods and compositions of the invention is a single-stranded antisense oligonucleotide molecule that inhibits a target mRNA via an antisense inhibition mechanism. The single-stranded antisense oligonucleotide molecule is complementary to a sequence within the target mRNA. The single-stranded antisense oligonucleotides can inhibit translation in a stoichiometric manner by base pairing to the mRNA and physically obstructing the translation machinery, see Dias, N. et al., (2002)  Mol Cancer Ther  1:347-355. The single-stranded antisense oligonucleotide molecule may be about 14 to about 30 nucleotides in length and have a sequence that is complementary to a target sequence. For example, the single-stranded antisense oligonucleotide molecule may comprise a sequence that is at least 14, 15, 16, 17, 18, 19, 20, or more contiguous nucleotides from any one of the antisense sequences described herein. 
     The phrase “contacting a cell with an iRNA,” such as a dsRNA, as used herein, includes contacting a cell by any possible means. Contacting a cell with an iRNA includes contacting a cell in vitro with the iRNA or contacting a cell in vivo with the iRNA. The contacting may be done directly or indirectly. Thus, for example, the iRNA may be put into physical contact with the cell by the individual performing the method, or alternatively, the iRNA may be put into a situation that will permit or cause it to subsequently come into contact with the cell. 
     Contacting a cell in vitro may be done, for example, by incubating the cell with the iRNA. Contacting a cell in vivo may be done, for example, by injecting the iRNA into or near the tissue where the cell is located, or by injecting the iRNA into another area, e.g., the bloodstream or the subcutaneous space, such that the agent will subsequently reach the tissue where the cell to be contacted is located. For example, the iRNA may contain or be coupled to a ligand, e.g., GalNAc, e.g., GalNAc3, that directs the iRNA to a site of interest, e.g., the liver. Combinations of in vitro and in vivo methods of contacting are also possible. For example, a cell may also be contacted in vitro with an iRNA and subsequently transplanted into a subject. 
     In certain embodiments, contacting a cell with an iRNA includes “introducing” or “delivering the iRNA into the cell” by facilitating or effecting uptake or absorption into the cell. Absorption or uptake of an iRNA can occur through unaided diffusion or active cellular processes, or by auxiliary agents or devices. Introducing an iRNA into a cell may be in vitro or in vivo. For example, for in vivo introduction, iRNA can be injected into a tissue site or administered systemically. In vivo delivery can also be done by a beta-glucan delivery system, such as those described in U.S. Pat. Nos. 5,032,401 and 5,607,677, and US Publication No. 2005/0281781, the entire contents of which are hereby incorporated herein by reference. In vitro introduction into a cell includes methods known in the art such as electroporation and lipofection. Further approaches are described herein below or are known in the art. 
     The term “lipid nanoparticle” or “LNP” is a vesicle comprising a lipid layer encapsulating a pharmaceutically active molecule, such as a nucleic acid molecule, e.g., an iRNA or a plasmid from which an iRNA is transcribed. LNPs are described in, for example, U.S. Pat. Nos. 6,858,225, 6,815,432, 8,158,601, and 8,058,069, the entire contents of which are hereby incorporated herein by reference. 
     As used herein, a “subject” is an animal, such as a mammal, including a primate (such as a human, a non-human primate, e.g., a monkey, and a chimpanzee), a non-primate (such as a cow, a pig, a camel, a llama, a horse, a goat, a rabbit, a sheep, a hamster, a guinea pig, a cat, a dog, a rat, a mouse, a horse, and a whale), or a bird (e.g., a duck or a goose) that expresses the target gene, either endogenously or heterologously, when the target gene sequence has sufficient complementarity to the iRNA agent to promote target knockdown. In certain embodiments, the subject is a human, such as a human being treated or assessed for a disease, disorder or condition that would benefit from reduction in PD-L1 gene expression or replication; a human at risk for a disease, disorder or condition that would benefit from reduction in PD-L1 gene expression; a human having a disease, disorder or condition that would benefit from reduction in PD-L1 gene expression; or human being treated for a disease, disorder or condition that would benefit from reduction in PD-L1 gene expression, as described herein. In some embodiments, the subject is a female human. In other embodiments, the subject is a male human. 
     As used herein, the terms “treating” or “treatment” refer to a beneficial or desired result including, but not limited to, alleviation or amelioration of one or more symptoms associated with PD-L1 gene expression or PD-L1 protein production, e.g., infection, especially a chronic, intracellular infection, e.g., a chronic viral infection, or cancer. “Treatment” can also mean prolonging survival as compared to expected survival in the absence of treatment. Treatment can include prevention of development of co-morbidities, e.g., reduced liver damage in a subject with a hepatic infection. 
     The term “lower” in the context of the level of PD-L1 gene expression or PD-L1 protein production in a subject, or a disease marker or symptom refers to a statistically significant decrease in such level. The decrease can be, for example, at least 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, as compared to an appropriate control, or to below the level of detection for the detection method. In certain embodiments, the expression of the target is normalized, i.e., decreased to a level accepted as within the range of normal for an individual without such disorder. In certain embodiments, the methods include a clinically relevant inhibition of expression of PD-L1, e.g. as demonstrated by a clinically relevant outcome after treatment of a subject with an agent to reduce the expression of PD-L1. 
     As used herein, the term “Programmed cell death 1 ligand 1-associated disease” or “PD-L1-associated disease,” is a disease or disorder that is caused by, or associated with PD-L1 gene expression or PD-L1 protein production. The term “PD-L1-associated disease” includes a disease, disorder or condition that would benefit from a decrease in PD-L1 gene expression, replication, or protein activity. Non-limiting examples of PD-L1-associated diseases include, for example, infection, especially a chronic intracellular infection, e.g., viral infection, e.g., hepatitis infection, or cancer. 
     In certain embodiments, a PD-L1-associated disease is infection, especially a chronic, intracellular infection, e.g., viral infection, e.g., hepatitis virus infection, e.g., hepatitis B infection or hepatitis D infection. In certain embodiments, the infection is a chronic bacterial infection, e.g., tuberculosis. In certain embodiments, a PD-L1-associated disease is cancer, especially liver cancer, e.g., heptatocellular carcinoma (HCC). 
     “Therapeutically effective amount,” as used herein, is intended to include the amount of an iRNA that, when administered to a patient for treating a subject having an infection, especially a chronic intracellular infection, or cancer, or other PD-L1-associated disease, is sufficient to effect treatment of the disease (e.g., by diminishing, ameliorating or maintaining the existing disease or one or more symptoms of disease or its related comorbidities). The “therapeutically effective amount” may vary depending on the iRNA, how it is administered, the disease and its severity and the history, age, weight, family history, genetic makeup, stage of pathological processes mediated by PD-L1 gene expression, the types of preceding or concomitant treatments, if any, and other individual characteristics of the patient to be treated. 
     A “therapeutically-effective amount” also includes an amount of an iRNA that produces some desired local or systemic effect at a reasonable benefit/risk ratio applicable to any treatment. iRNAs employed in the methods of the present invention may be administered in a sufficient amount to produce a reasonable benefit/risk ratio applicable to such treatment. A therapeutically effective amount includes an amount that results in a clinically relevant change or stabilization, as appropriate, of an indicator of a disease or condition. 
     The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human subjects and animal subjects without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. 
     The phrase “pharmaceutically-acceptable carrier” as used herein means a pharmaceutically-acceptable material, composition, or vehicle, such as a liquid or solid filler, diluent, excipient, manufacturing aid (e.g., lubricant, talc magnesium, calcium or zinc stearate, or steric acid), or solvent encapsulating material, involved in carrying or transporting the subject compound from one organ, or portion of the body, to another organ, or portion of the body. Each carrier must be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the subject being treated. Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) lubricating agents, such as magnesium state, sodium lauryl sulfate and talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer&#39;s solution; (19) ethyl alcohol; (20) pH buffered solutions; (21) polyesters, polycarbonates and/or polyanhydrides; (22) bulking agents, such as polypeptides and amino acids (23) serum component, such as serum albumin, HDL and LDL; and (22) other non-toxic compatible substances employed in pharmaceutical formulations. 
     The term “sample,” as used herein, includes a collection of similar fluids, cells, or tissues isolated from a subject, as well as fluids, cells, or tissues present within a subject. Examples of biological fluids include blood, serum and serosal fluids, plasma, cerebrospinal fluid, ocular fluids, lymph, urine, saliva, and the like. Tissue samples may include samples from tissues, organs, or localized regions. For example, samples may be derived from particular organs, parts of organs, or fluids or cells within those organs. In certain embodiments, samples may be derived from the liver (e.g., whole liver or certain segments of liver or certain types of cells in the liver, such as, e.g., hepatocytes). A “sample derived from a subject” can refer to blood drawn from the subject, or plasma derived therefrom. In certain embodiments when detecting a level of PD-L1, a “sample” preferably refers to a tissue or body fluid from a subject in which PD-L1 is detectable prior to administration of an agent of the invention, e.g., a liver biopsy from a subject with a hepatic infection, a tumor biopsy. In certain subjects, e.g., healthy subjects, the level of PD-L1 may not be detectable in a number of body fluids, cell types, and tissues. 
     I. iRNAs of the Invention 
     The present invention provides iRNAs which inhibit the expression of a PD-L1 gene. In preferred embodiments, the iRNA includes double stranded ribonucleic acid (dsRNA) molecules for inhibiting the expression of a PD-L1 gene in a cell, such as a cell within a subject, e.g., a mammal, such as a human having a PD-L1-associated disease, e.g., a chronic infection. The dsRNAi agent includes an antisense strand having a region of complementarity which is complementary to at least a part of an mRNA formed in the expression of a PD-L1 gene. The region of complementarity is about 30 nucleotides or less in length (e.g., about 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, or 18 nucleotides or less in length). Upon contact with a cell expressing the PD-L1 gene, the iRNA inhibits the expression of the PD-L1 gene (e.g., a human, a primate, a non-primate, or a bird PD-L1 gene) by at least about 20%, preferably by at least 30%, as assayed by, for example, a PCR or branched DNA (bDNA)-based method, or by a protein-based method, such as by immunofluorescence analysis, using, for example, western blotting or flowcytometric techniques. In preferred embodiments, inhibition of expression is determined by the qPCR method provided in the examples, e.g., at a 10 nM concentration of the duplex. The level of reduction can be compared to, for example, an appropriate historical control or a pooled population sample control. 
     A dsRNA includes two RNA strands that are complementary and hybridize to form a duplex structure under conditions in which the dsRNA will be used. One strand of a dsRNA (the antisense strand) includes a region of complementarity that is substantially complementary, and generally fully complementary, to a target sequence. The target sequence can be derived from the sequence of an mRNA formed during the expression of a PD-L1 gene. The other strand (the sense strand) includes a region that is complementary to the antisense strand, such that the two strands hybridize and form a duplex structure when combined under suitable conditions. As described elsewhere herein and as known in the art, the complementary sequences of a dsRNA can also be contained as self-complementary regions of a single nucleic acid molecule, as opposed to being on separate oligonucleotides. 
     Generally, the duplex structure is about 15 to 30 base pairs in length, e.g., 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 base pairs in length. Ranges and lengths intermediate to the above recited ranges and lengths are also contemplated to be part of the invention. 
     Similarly, the region of complementarity to the target sequence is about 15 to 30 nucleotides in length, e.g., 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 nucleotides in length. Ranges and lengths intermediate to the above recited ranges and lengths are also contemplated to be part of the invention. 
     In some embodiments, the dsRNA is about 15 to 23 nucleotides in length, or about 25 to 30 nucleotides in length. In general, the dsRNA is long enough to serve as a substrate for the Dicer enzyme. For example, it is well-known in the art that dsRNAs longer than about 21-23 nucleotides in length may serve as substrates for Dicer. As the ordinarily skilled person will also recognize, the region of an RNA targeted for cleavage will most often be part of a larger RNA molecule, often an mRNA molecule. Where relevant, a “part” of an mRNA target is a contiguous sequence of an mRNA target of sufficient length to allow it to be a substrate for RNAi-directed cleavage (i.e., cleavage through a RISC pathway). 
     One of skill in the art will also recognize that the duplex region is a primary functional portion of a dsRNA, e.g., a duplex region of about 9 to about 36 base pairs, e.g., 10-36, 11-36, 12-36, 13-36, 14-36, 15-36, 9-35, 10-35, 11-35, 12-35, 13-35, 14-35, 15-35, 9-34, 10-34, 11-34, 12-34, 13-34, 14-34, 15-34, 9-33, 10-33, 11-33, 12-33, 13-33, 14-33, 15-33, 9-32, 10-32, 11-32, 12-32, 13-32, 14-32, 15-32, 9-31, 10-31, 11-31, 12-31, 13-32, 14-31, 15-31, 15-30, 15-29, 15-28, 15-27, 15-26, 15-25, 15-24, 15-23, 15-22, 15-21, 15-20, 15-19, 15-18, 15-17, 18-30, 18-29, 18-28, 18-27, 18-26, 18-25, 18-24, 18-23, 18-22, 18-21, 18-20, 19-30, 19-29, 19-28, 19-27, 19-26, 19-25, 19-24, 19-23, 19-22, 19-21, 19-20, 20-30, 20-29, 20-28, 20-27, 20-26, 20-25, 20-24, 20-23, 20-22, 20-21, 21-30, 21-29, 21-28, 21-27, 21-26, 21-25, 21-24, 21-23, or 21-22 base pairs. Thus, in one embodiment, to the extent that it becomes processed to a functional duplex, of e.g., 15-30 base pairs, that targets a desired RNA for cleavage, an RNA molecule or complex of RNA molecules having a duplex region greater than 30 base pairs is a dsRNA. Thus, an ordinarily skilled artisan will recognize that in one embodiment, a miRNA is a dsRNA. In another embodiment, a dsRNA is not a naturally occurring miRNA. In another embodiment, an iRNA agent useful to target PD-L1 gene expression is not generated in the target cell by cleavage of a larger dsRNA. 
     A dsRNA as described herein can further include one or more single-stranded nucleotide overhangs e.g., 1-4, 2-4, 1-3, 2-3, 1, 2, 3, or 4 nucleotides. dsRNAs having at least one nucleotide overhang can have superior inhibitory properties relative to their blunt-ended counterparts. A nucleotide overhang can comprise or consist of a nucleotide/nucleoside analog, including a deoxynucleotide/nucleoside. The overhang(s) can be on the sense strand, the antisense strand, or any combination thereof. Furthermore, the nucleotide(s) of an overhang can be present on the 5′-end, 3′-end, or both ends of an antisense or sense strand of a dsRNA. 
     A dsRNA can be synthesized by standard methods known in the art as further discussed below, e.g., by use of an automated DNA synthesizer, such as are commercially available from, for example, Biosearch, Applied Biosystems, Inc. 
     Double stranded RNAi compounds of the invention may be prepared using a two-step procedure. First, the individual strands of the double stranded RNA molecule are prepared separately. Then, the component strands are annealed. The individual strands of the siRNA compound can be prepared using solution-phase or solid-phase organic synthesis or both. Organic synthesis offers the advantage that the oligonucleotide strands comprising unnatural or modified nucleotides can be easily prepared. Similarly, single-stranded oligonucleotides of the invention can be prepared using solution-phase or solid-phase organic synthesis or both. 
     In an aspect, a dsRNA of the invention includes at least two nucleotide sequences, a sense sequence and an anti-sense sequence. The sense strand is selected from the group of sequences provided in Tables 3 and 5, and the corresponding antisense strand of the sense strand is selected from the group of sequences of Tables 3 and 5. In this aspect, one of the two sequences is complementary to the other of the two sequences, with one of the sequences being substantially complementary to a sequence of an mRNA generated in the expression of a PD-L1 gene. As such, in this aspect, a dsRNA will include two oligonucleotides, where one oligonucleotide is described as the sense strand in Table 3 or 5, and the second oligonucleotide is described as the corresponding antisense strand of the sense strand in Table 3 or 5. In certain embodiments, the substantially complementary sequences of the dsRNA are contained on separate oligonucleotides. In other embodiments, the substantially complementary sequences of the dsRNA are contained on a single oligonucleotide. 
     It will be understood that, although the sequences in Table 3 are not described as modified or conjugated sequences, the RNA of the iRNA of the invention e.g., a dsRNA of the invention, may comprise any one of the sequences set forth in Table 3, or the sequences of Table 5 that are modified, or the sequences of Table 5 that are conjugated. In other words, the invention encompasses dsRNA of Tables 3 and 5 which are un-modified, un-conjugated, modified, or conjugated, as described herein. 
     The skilled person is well aware that dsRNAs having a duplex structure of between about 20 and 23 base pairs, e.g., 21, base pairs have been hailed as particularly effective in inducing RNA interference (Elbashir et al.,  EMBO  2001, 20:6877-6888). However, others have found that shorter or longer RNA duplex structures can also be effective (Chu and Rana (2007)  RNA  14:1714-1719; Kim et al. (2005)  Nat Biotech  23:222-226). In the embodiments described above, by virtue of the nature of the oligonucleotide sequences provided in any one of Tables 3 and 5, dsRNAs described herein can include at least one strand of a length of minimally 21 nucleotides. It can be reasonably expected that shorter duplexes having one of the sequences of Tables 3 and 5 minus only a few nucleotides on one or both ends can be similarly effective as compared to the dsRNAs described above. Hence, dsRNAs having a sequence of at least 15, 16, 17, 18, 19, 20, or more contiguous nucleotides derived from one of the sequences of Tables 3 and 5, and differing in their ability to inhibit the expression of a PD-L1 gene by not more than about 5, 10, 15, 20, 25, or 30% inhibition from a dsRNA comprising the full sequence, are contemplated to be within the scope of the present invention. 
     In addition, the RNAs provided in Tables 3 and 5 identify a site(s) in a PD-L1 transcript that is susceptible to RISC-mediated cleavage. As such, the present invention further features iRNAs that target within one of these sites. As used herein, an iRNA is said to target within a particular site of an RNA transcript if the iRNA promotes cleavage of the transcript anywhere within that particular site. Such an iRNA will generally include at least about 15 contiguous nucleotides from one of the sequences provided in Tables 3 and 5 coupled to additional nucleotide sequences taken from the region contiguous to the selected sequence in a PD-L1 gene. 
     While a target sequence is generally about 15-30 nucleotides in length, there is wide variation in the suitability of particular sequences in this range for directing cleavage of any given target RNA. Various software packages and the guidelines set out herein provide guidance for the identification of optimal target sequences for any given gene target, but an empirical approach can also be taken in which a “window” or “mask” of a given size (as a non-limiting example, 21 nucleotides) is literally or figuratively (including, e.g., in silico) placed on the target RNA sequence to identify sequences in the size range that can serve as target sequences. By moving the sequence “window” progressively one nucleotide upstream or downstream of an initial target sequence location, the next potential target sequence can be identified, until the complete set of possible sequences is identified for any given target size selected. This process, coupled with systematic synthesis and testing of the identified sequences (using assays as described herein or as known in the art or provided herein) to identify those sequences that perform optimally can identify those RNA sequences that, when targeted with an iRNA agent, mediate the best inhibition of target gene expression. Thus, while the sequences identified, for example, in Tables 3 and 5 represent effective target sequences, it is contemplated that further optimization of inhibition efficiency can be achieved by progressively “walking the window” one nucleotide upstream or downstream of the given sequences to identify sequences with equal or better inhibition characteristics. 
     Further, it is contemplated that for any sequence identified, e.g., in Tables 3 and 5, further optimization could be achieved by systematically either adding or removing nucleotides to generate longer or shorter sequences and testing those sequences generated by walking a window of the longer or shorter size up or down the target RNA from that point. Again, coupling this approach to generating new candidate targets with testing for effectiveness of iRNAs based on those target sequences in an inhibition assay as known in the art or as described herein can lead to further improvements in the efficiency of inhibition. Further still, such optimized sequences can be adjusted by, e.g., the introduction of modified nucleotides as described herein or as known in the art, addition or changes in overhang, or other modifications as known in the art or discussed herein to further optimize the molecule (e.g., increasing serum stability or circulating half-life, increasing thermal stability, enhancing transmembrane delivery, targeting to a particular location or cell type, increasing interaction with silencing pathway enzymes, increasing release from endosomes) as an expression inhibitor. 
     An iRNA as described herein can contain one or more mismatches to the target sequence. In one embodiment, an iRNA as described herein contains no more than 3 mismatches. If the antisense strand of the iRNA contains mismatches to a target sequence, it is preferable that the area of mismatch is not located in the center of the region of complementarity. If the antisense strand of the iRNA contains mismatches to the target sequence, it is preferable that the mismatch be restricted to be within the last 5 nucleotides from either the 5′- or 3′-end of the region of complementarity. For example, for a 23 nucleotide iRNA agent the strand which is complementary to a region of a PD-L1 gene, generally does not contain any mismatch within the central 13 nucleotides. The methods described herein or methods known in the art can be used to determine whether an iRNA containing a mismatch to a target sequence is effective in inhibiting the expression of a PD-L1 gene. Consideration of the efficacy of iRNAs with mismatches in inhibiting expression of a PD-L1 gene is important, especially if the particular region of complementarity in a PD-L1 gene is known to have polymorphic sequence variation within the population. 
     II. Modified iRNAs of the Invention 
     In certain embodiments, the RNA of the iRNA of the invention e.g., a dsRNA, is unmodified, and does not comprise, e.g., chemical modifications or conjugations known in the art and described herein. In other embodiments, the RNA of an iRNA of the invention, e.g., a dsRNA, is chemically modified to enhance stability or other beneficial characteristics. In certain embodiments of the invention, substantially all of the nucleotides of an iRNA of the invention are modified. In other embodiments of the invention, all of the nucleotides of an iRNA or substantially all of the nucleotides of an iRNA are modified, i.e., not more than 5, 4, 3, 2, or 1 unmodified nucleotides are present in a strand of the iRNA. 
     The nucleic acids featured in the invention can be synthesized or modified by methods well established in the art, such as those described in “Current protocols in nucleic acid chemistry,” Beaucage, S. L. et al. (Edrs.), John Wiley &amp; Sons, Inc., New York, N.Y., USA, which is hereby incorporated herein by reference. Modifications include, for example, end modifications, e.g., 5′-end modifications (phosphorylation, conjugation, inverted linkages) or 3′-end modifications (conjugation, DNA nucleotides, inverted linkages, etc.); base modifications, e.g., replacement with stabilizing bases, destabilizing bases, or bases that base pair with an expanded repertoire of partners, removal of bases (abasic nucleotides), or conjugated bases; sugar modifications (e.g., at the 2′-position or 4′-position) or replacement of the sugar; or backbone modifications, including modification or replacement of the phosphodiester linkages. Specific examples of iRNA compounds useful in the embodiments described herein include, but are not limited to RNAs containing modified backbones or no natural internucleoside linkages. RNAs having modified backbones include, among others, those that do not have a phosphorus atom in the backbone. For the purposes of this specification, and as sometimes referenced in the art, modified RNAs that do not have a phosphorus atom in their internucleoside backbone can also be considered to be oligonucleosides. In some embodiments, a modified iRNA will have a phosphorus atom in its internucleoside backbone. 
     Modified RNA backbones include, for example, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates including 3′-alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates including 3′-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3′-5′ linkages, 2′-5′-linked analogs of these, and those having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′. Various salts, mixed salts and free acid forms are also included. 
     Representative US Patents that teach the preparation of the above phosphorus-containing linkages include, but are not limited to, U.S. Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,195; 5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131; 5,399,676; 5,405,939; 5,453,496; 5,455,233; 5,466,677; 5,476,925; 5,519,126; 5,536,821; 5,541,316; 5,550,111; 5,563,253; 5,571,799; 5,587,361; 5,625,050; 6,028,188; 6,124,445; 6,160,109; 6,169,170; 6,172,209; 6,239,265; 6,277,603; 6,326,199; 6,346,614; 6,444,423; 6,531,590; 6,534,639; 6,608,035; 6,683,167; 6,858,715; 6,867,294; 6,878,805; 7,015,315; 7,041,816; 7,273,933; 7,321,029; and U.S. Pat. No. RE39464, the entire contents of each of which are hereby incorporated herein by reference. 
     Modified RNA backbones that do not include a phosphorus atom therein have backbones that are formed by short chain alkyl or cycloalkyl internucleoside linkages, mixed heteroatoms and alkyl or cycloalkyl internucleoside linkages, or one or more short chain heteroatomic or heterocyclic internucleoside linkages. These include those having morpholino linkages (formed in part from the sugar portion of a nucleoside); siloxane backbones; sulfide, sulfoxide and sulfone backbones; formacetyl and thioformacetyl backbones; methylene formacetyl and thioformacetyl backbones; alkene containing backbones; sulfamate backbones; methyleneimino and methylenehydrazino backbones; sulfonate and sulfonamide backbones; amide backbones; and others having mixed N, O, S, and CH 2  component parts. 
     Representative US Patents that teach the preparation of the above oligonucleosides include, but are not limited to, U.S. Pat. Nos. 5,034,506; 5,166,315; 5,185,444; 5,214,134; 5,216,141; 5,235,033; 5,64,562; 5,264,564; 5,405,938; 5,434,257; 5,466,677; 5,470,967; 5,489,677; 5,541,307; 5,561,225; 5,596,086; 5,602,240; 5,608,046; 5,610,289; 5,618,704; 5,623,070; 5,663,312; 5,633,360; 5,677,437; and 5,677,439, the entire contents of each of which are hereby incorporated herein by reference. 
     Suitable RNA mimetics are contemplated for use in iRNAs provided herein, in which both the sugar and the internucleoside linkage, i.e., the backbone, of the nucleotide units are replaced with novel groups. The base units are maintained for hybridization with an appropriate nucleic acid target compound. One such oligomeric compound in which an RNA mimetic that has been shown to have excellent hybridization properties is referred to as a peptide nucleic acid (PNA). In PNA compounds, the sugar backbone of an RNA is replaced with an amide containing backbone, in particular an aminoethylglycine backbone. The nucleobases are retained and are bound directly or indirectly to aza nitrogen atoms of the amide portion of the backbone. Representative US patents that teach the preparation of PNA compounds include, but are not limited to, U.S. Pat. Nos. 5,539,082; 5,714,331; and 5,719,262, the entire contents of each of which are hereby incorporated herein by reference. Additional PNA compounds suitable for use in the iRNAs of the invention are described in, for example, in Nielsen et al.,  Science,  1991, 254, 1497-1500. 
     Some embodiments featured in the invention include RNAs with phosphorothioate backbones and oligonucleosides with heteroatom backbones, and in particular —CH 2 —NH—CH 2 -, —CH 2 —N(CH 3 )—O-CH 2 -[known as a methylene (methylimino) or MMI backbone], —CH 2 —O—N(CH 3 )—CH 2 —, —CH 2 —N(CH 3 )—N(CH 3 )—CH 2 —and —N(CH 3 )—CH 2 —CH 2 -[wherein the native phosphodiester backbone is represented as —O—P-O-CH 2 —] of the above-referenced U.S. Pat. No. 5,489,677, and the amide backbones of the above-referenced U.S. Pat. No. 5,602,240. In some embodiments, the RNAs featured herein have morpholino backbone structures of the above-referenced U.S. Pat. No. 5,034,506. 
     Modified RNAs can also contain one or more substituted sugar moieties. The iRNAs, e.g., dsRNAs, featured herein can include one of the following at the 2′-position: OH; F; O-, S-, or N-alkyl; O-, S-, or N-alkenyl; O-, S- or N-alkynyl; or O-alkyl-O-alkyl, wherein the alkyl, alkenyl and alkynyl can be substituted or unsubstituted C 1  to C 10  alkyl or C 2  to C 10  alkenyl and alkynyl. Exemplary suitable modifications include O[(CH 2 ) n O] m CH 3 , O(CH 2 ). n OCH 3 , O(CH 2 ) n NH 2 , O(CH 2 ) n CH 3 , O(CH 2 ) n ONH 2 , and O(CH 2 ) n ON[(CH 2 ) n CH 3 )] 2 , where n and m are from 1 to about 10. In other embodiments, dsRNAs include one of the following at the 2′ position: C 1  to C 10  lower alkyl, substituted lower alkyl, alkaryl, aralkyl, O-alkaryl or O-aralkyl, SH, SCH 3 , OCN, Cl, Br, CN, CF 3 , OCF 3 , SOCH 3 , SO 2 CH 3 , ONO 2 , NO 2 , N 3 , NH 2 , heterocycloalkyl, heterocycloalkaryl, aminoalkylamino, polyalkylamino, substituted silyl, an RNA cleaving group, a reporter group, an intercalator, a group for improving the pharmacokinetic properties of an iRNA, or a group for improving the pharmacodynamic properties of an iRNA, and other substituents having similar properties. In some embodiments, the modification includes a 2′-methoxyethoxy (2′-O-CH 2 CH 2 OCH 3 , also known as 2′-O-(2-methoxyethyl) or 2′-MOE) (Martin et al.,  Helv. Chim. Acta,  1995, 78:486-504) i.e., an alkoxy-alkoxy group. Another exemplary modification is 2′-dimethylaminooxyethoxy, i.e., a O(CH 2 ) 2 ON(CH 3 ) 2  group, also known as 2′-DMAOE, as described in examples herein below, and 2′-dimethylaminoethoxyethoxy (also known in the art as 2′-O-dimethylaminoethoxyethyl or 2′-DMAEOE), i.e., 2′-O—CH 2 —O—CH 2 —N(CH 2 ) 2 . Further exemplary modifications include: 5′-Me-2′-F nucleotides, 5′-Me-2′-OMe nucleotides, 5′-Me-2′-deoxynucleotides, (both R and S isomers in these three families); 2′-alkoxyalkyl; and 2′-NMA (N-methylacetamide). 
     Other modifications include 2′-methoxy (2′-OCH 3 ), 2′-aminopropoxy (2′-OCH 2 CH 2 CH 2 NH 2 ) and 2′-fluoro (2′-F). Similar modifications can also be made at other positions on the RNA of an iRNA, particularly the 3′ position of the sugar on the 3′ terminal nucleotide or in 2′-5′ linked dsRNAs and the 5′ position of 5′ terminal nucleotide. iRNAs can also have sugar mimetics such as cyclobutyl moieties in place of the pentofuranosyl sugar. Representative US patents that teach the preparation of such modified sugar structures include, but are not limited to, U.S. Pat. Nos. 4,981,957; 5,118,800; 5,319,080; 5,359,044; 5,393,878; 5,446,137; 5,466,786; 5,514,785; 5,519,134; 5,567,811; 5,576,427; 5,591,722; 5,597,909; 5,610,300; 5,627,053; 5,639,873; 5,646,265; 5,658,873; 5,670,633; and 5,700,920, certain of which are commonly owned with the instant application. The entire contents of each of the foregoing are hereby incorporated herein by reference. 
     An iRNA can also include nucleobase (often referred to in the art simply as “base”) modifications or substitutions. As used herein, “unmodified” or “natural” nucleobases include the purine bases adenine (A) and guanine (G), and the pyrimidine bases thymine (T), cytosine (C), and uracil (U). Modified nucleobases include other synthetic and natural nucleobases such as deoxy-thymine (dT), 5-methylcytosine (5-me-C), 5-hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives of adenine and guanine, 2-propyl and other alkyl derivatives of adenine and guanine, 2-thiouracil, 2-thiothymine and 2-thiocytosine, 5-halouracil and cytosine, 5-propynyl uracil and cytosine, 6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil), 4-thiouracil, 8-halo, 8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl anal other 8-substituted adenines and guanines, 5-halo, particularly 5-bromo, 5-trifluoromethyl and other 5-substituted uracils and cytosines, 7-methylguanine and 7-methyladenine, 8-azaguanine and 8-azaadenine, 7-deazaguanine and 7-deazaadenine and 3-deazaguanine and 3-deazaadenine. Further nucleobases include those disclosed in U.S. Pat. No. 3,687,808, those disclosed in Modified Nucleosides in Biochemistry, Biotechnology and Medicine, Herdewijn, P. ed. Wiley-VCH, 2008; those disclosed in The Concise Encyclopedia Of Polymer Science And Engineering, pages 858-859, Kroschwitz, J. L, ed. John Wiley &amp; Sons, 1990, these disclosed by Englisch et al., Angewandte Chemie, International Edition, 1991, 30, 613, and those disclosed by Sanghvi, Y S., Chapter 15, dsRNA Research and Applications, pages 289-302, Crooke, S. T. and Lebleu, B., Ed., CRC Press, 1993. Certain of these nucleobases are particularly useful for increasing the binding affinity of the oligomeric compounds featured in the invention. These include 5-substituted pyrimidines, 6-azapyrimidines and N-2, N-6 and 0-6 substituted purines, including 2-aminopropyladenine, 5-propynyluracil and 5-propynylcytosine. 5-methylcytosine substitutions have been shown to increase nucleic acid duplex stability by 0.6-1.2° C. (Sanghvi, Y. S., Crooke, S. T. and Lebleu, B., Eds., dsRNA Research and Applications, CRC Press, Boca Raton, 1993, pp. 276-278) and are exemplary base substitutions, even more particularly when combined with 2′-O-methoxyethyl sugar modifications. 
     Representative US Patents that teach the preparation of certain of the above noted modified nucleobases as well as other modified nucleobases include, but are not limited to, the above noted U.S. Pat. Nos. 3,687,808, 4,845,205; 5,130,30; 5,134,066; 5,175,273; 5,367,066; 5,432,272; 5,457,187; 5,459,255; 5,484,908; 5,502,177; 5,525,711; 5,552,540; 5,587,469; 5,594,121, 5,596,091; 5,614,617; 5,681,941; 5,750,692; 6,015,886; 6,147,200; 6,166,197; 6,222,025; 6,235,887; 6,380,368; 6,528,640; 6,639,062; 6,617,438; 7,045,610; 7,427,672; and 7,495,088, the entire contents of each of which are hereby incorporated herein by reference. 
     The RNA of an iRNA can also be modified to include one or more locked nucleic acids (LNA). A locked nucleic acid is a nucleotide having a modified ribose moiety in which the ribose moiety comprises an extra bridge connecting the 2′ and 4′ carbons. This structure effectively “locks” the ribose in the 3′-endo structural conformation. The addition of locked nucleic acids to siRNAs has been shown to increase siRNA stability in serum, and to reduce off-target effects (Elmen, J. et al., (2005)  Nucleic Acids Research  33(1):439-447; Mook, O R. et al., (2007)  Mol Canc Ther  6(3):833-843; Grunweller, A. et al., (2003)  Nucleic Acids Research  31(12):3185-3193). 
     In some embodiments, the iRNA of the invention comprises one or more monomers that are UNA (unlocked nucleic acid) nucleotides. UNA is unlocked acyclic nucleic acid, wherein any of the bonds of the sugar has been removed, forming an unlocked “sugar” residue. In one example, UNA also encompasses monomer with bonds between C1′-C4′ have been removed (i.e. the covalent carbon-oxygen-carbon bond between the C1′ and C4′ carbons). In another example, the C2′-C3′ bond (i.e. the covalent carbon-carbon bond between the C2′ and C3′ carbons) of the sugar has been removed (see Nuc. Acids Symp. Series, 52, 133-134 (2008) and Fluiter et al.,  Mol. Biosyst.,  2009, 10, 1039 hereby incorporated by reference). 
     The RNA of an iRNA can also be modified to include one or more bicyclic sugar moities. A “bicyclic sugar” is a furanosyl ring modified by the bridging of two atoms. A “bicyclic nucleoside” (“BNA”) is a nucleoside having a sugar moiety comprising a bridge connecting two carbon atoms of the sugar ring, thereby forming a bicyclic ring system. In certain embodiments, the bridge connects the 4′-carbon and the 2′-carbon of the sugar ring. Thus, in some embodiments an agent of the invention may include one or more locked nucleic acids (LNA). A locked nucleic acid is a nucleotide having a modified ribose moiety in which the ribose moiety comprises an extra bridge connecting the 2′ and 4′ carbons. In other words, an LNA is a nucleotide comprising a bicyclic sugar moiety comprising a 4′-CH 2 -O-2′ bridge. This structure effectively “locks” the ribose in the 3′-endo structural conformation. The addition of locked nucleic acids to siRNAs has been shown to increase siRNA stability in serum, and to reduce off-target effects (Elmen, J. et al., (2005)  Nucleic Acids Research  33(1):439-447; Mook, O R. et al., (2007)  Mol Canc Ther  6(3):833-843; Grunweller, A. et al., (2003)  Nucleic Acids Research  31(12):3185-3193). Examples of bicyclic nucleosides for use in the polynucleotides of the invention include without limitation nucleosides comprising a bridge between the 4′ and the 2′ ribosyl ring atoms. In certain embodiments, the antisense polynucleotide agents of the invention include one or more bicyclic nucleosides comprising a 4′ to 2′ bridge. Examples of such 4′ to 2′ bridged bicyclic nucleosides, include but are not limited to 4′-(CH 2 )—O-2′ (LNA); 4′-(CH 2 )—S-2; 4′-(CH 2 ) 2 -O-2′ (ENA); 4′-CH(CH 3 )—O-2′ (also referred to as “constrained ethyl” or “cEt”) and 4′-CH(CH 2 OCH 3 )—O-2′ (and analogs thereof; see, e.g., U.S. Pat. No. 7,399,845); 4′-C(CH 3 )(CH 3 )—O-2′ (and analogs thereof; see e.g., U.S. Pat. No. 8,278,283); 4′-CH 2 —N(OCH 3 )-2′ (and analogs thereof; see e.g., U.S. Pat. No. 8,278,425); 4′-CH 2 -O—N(CH 3 )-2′ (see, e.g., US Patent Publication No. 2004/0171570); 4′-CH 2 —N(R)-O-2′, wherein R is H, C1-C12 alkyl, or a protecting group (see, e.g., U.S. Pat. No. 7,427,672); 4′-CH 2 —C(H)(CH 3 )-2′ (see, e.g., Chattopadhyaya et al.,  J. Org. Chem.,  2009, 74, 118-134); and 4′-CH 2 —C(H 2 )-2′ (and analogs thereof; see, e.g., U.S. Pat. No. 8,278,426). The entire contents of each of the foregoing are hereby incorporated herein by reference. 
     Additional representative US Patents and US Patent Publications that teach the preparation of locked nucleic acid nucleotides include, but are not limited to, the following: U.S. Pat. Nos. 6,268,490; 6,525,191; 6,670,461; 6,770,748; 6,794,499; 6,998,484; 7,053,207; 7,034,133; 7,084,125; 7,399,845; 7,427,672; 7,569,686; 7,741,457; 8,022,193; 8,030,467; 8,278,425; 8,278,426; 8,278,283; US 2008/0039618; and US 2009/0012281, the entire contents of each of which are hereby incorporated herein by reference. 
     Any of the foregoing bicyclic nucleosides can be prepared having one or more stereochemical sugar configurations including for example α-L-ribofuranose and β-D-ribofuranose (see WO 99/14226). 
     The RNA of an iRNA can also be modified to include one or more constrained ethyl nucleotides. As used herein, a “constrained ethyl nucleotide” or “cEt” is a locked nucleic acid comprising a bicyclic sugar moiety comprising a 4′-CH(CH 3 )—O-2′ bridge. In one embodiment, a constrained ethyl nucleotide is in the S conformation referred to herein as “S-cEt.” 
     An iRNA of the invention may also include one or more “conformationally restricted nucleotides” (“CRN”). CRN are nucleotide analogs with a linker connecting the C2′ and C4′ carbons of ribose or the C3 and C5′ carbons of ribose. CRN lock the ribose ring into a stable conformation and increase the hybridization affinity to mRNA. The linker is of sufficient length to place the oxygen in an optimal position for stability and affinity resulting in less ribose ring puckering. 
     Representative publications that teach the preparation of certain of the above noted CRN include, but are not limited to, US Patent Publication No. 2013/0190383; and PCT publication WO 2013/036868, the entire contents of each of which are hereby incorporated herein by reference. 
     In some embodiments, the iRNA of the invention comprises one or more monomers that are UNA (unlocked nucleic acid) nucleotides. UNA is unlocked acyclic nucleic acid, wherein any of the bonds of the sugar has been removed, forming an unlocked “sugar” residue. In one example, UNA also encompasses monomer with bonds between C1′-C4′ have been removed (i.e. the covalent carbon-oxygen-carbon bond between the C1′ and C4′ carbons). In another example, the C2′-C3′ bond (i.e. the covalent carbon-carbon bond between the C2′ and C3′ carbons) of the sugar has been removed (see Nuc. Acids Symp. Series, 52, 133-134 (2008) and Fluiter et al.,  Mol. Biosyst.,  2009, 10, 1039 hereby incorporated by reference). 
     Representative US publications that teach the preparation of UNA include, but are not limited to, U.S. Pat. No. 8,314,227; and US Patent Publication Nos. 2013/0096289; 2013/0011922; and 2011/0313020, the entire contents of each of which are hereby incorporated herein by reference. 
     Potentially stabilizing modifications to the ends of RNA molecules can include N-(acetylaminocaproyl)-4-hydroxyprolinol (Hyp-C6-NHAc), N-(caproyl-4-hydroxyprolinol (Hyp-C6), N-(acetyl-4-hydroxyprolinol (Hyp-NHAc), thymidine-2′-O-deoxythymidine (ether), N-(aminocaproyl)-4-hydroxyprolinol (Hyp-C6-amino), 2-docosanoyl-uridine-3″-phosphate, inverted base dT(idT) and others. Disclosure of this modification can be found in PCT Publication No. WO 2011/005861. 
     Other modifications of the nucleotides of an iRNA of the invention include a 5′ phosphate or 5′ phosphate mimic, e.g., a 5′-terminal phosphate or phosphate mimic on the antisense strand of an iRNA. Suitable phosphate mimics are disclosed in, for example US Patent Publication No. 2012/0157511, the entire contents of which are incorporated herein by reference. 
     A. Modified iRNAs Comprising Motifs of the Invention 
     In certain aspects of the invention, the double stranded RNAi agents of the invention include agents with chemical modifications as disclosed, for example, in WO2013/075035, the entire contents of each of which are incorporated herein by reference. WO2013/075035 provides motifs of three identical modifications on three consecutive nucleotides into a sense strand or antisense strand of a dsRNAi agent, particularly at or near the cleavage site. In some embodiments, the sense strand and antisense strand of the dsRNAi agent may otherwise be completely modified. The introduction of these motifs interrupts the modification pattern, if present, of the sense or antisense strand. The dsRNAi agent may be optionally conjugated with a GalNAc derivative ligand, for instance on the sense strand. 
     More specifically, when the sense strand and antisense strand of the double stranded RNAi agent are completely modified to have one or more motifs of three identical modifications on three consecutive nucleotides at or near the cleavage site of at least one strand of a dsRNAi agent, the gene silencing activity of the dsRNAi agent was observed. 
     Accordingly, the invention provides double stranded RNAi agents capable of inhibiting the expression of a target gene (i.e., PD-L1 gene) in vivo. The RNAi agent comprises a sense strand and an antisense strand. Each strand of the RNAi agent may be, independently, 12-30 nucleotides in length. For example, each strand may independently be 14-30 nucleotides in length, 17-30 nucleotides in length, 25-30 nucleotides in length, 27-30 nucleotides in length, 17-23 nucleotides in length, 17-21 nucleotides in length, 17-19 nucleotides in length, 19-25 nucleotides in length, 19-23 nucleotides in length, 19-21 nucleotides in length, 21-25 nucleotides in length, or 21-23 nucleotides in length. 
     The sense strand and antisense strand typically form a duplex double stranded RNA (“dsRNA”), also referred to herein as “dsRNAi agent.” The duplex region of an dsRNAi agent may be 12-30 nucleotide pairs in length. For example, the duplex region can be 14-30 nucleotide pairs in length, 17-30 nucleotide pairs in length, 27-30 nucleotide pairs in length, 17-23 nucleotide pairs in length, 17-21 nucleotide pairs in length, 17-19 nucleotide pairs in length, 19-25 nucleotide pairs in length, 19-23 nucleotide pairs in length, 19-21 nucleotide pairs in length, 21-25 nucleotide pairs in length, or 21-23 nucleotide pairs in length. In another example, the duplex region is selected from 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 nucleotides in length. 
     In certain embodiments, the sense and antisense strands may be even longer. For example, in certain embodiments, the sense strand and the antisense strand are independently 25-35 nucleotides in length. In certain embodiments, each the sense and the antisense strand are independently 27-53 nucleotides in length, e.g., 27-49, 31-49, 33-49, 35-49, 37-49, and 39-49 nucleotides in length. 
     In certain embodiments, the dsRNAi agent may contain one or more overhang regions or capping groups at the 3′-end, 5′-end, or both ends of one or both strands. The overhang can be, independently, 1-6 nucleotides in length, for instance 2-6 nucleotides in length, 1-5 nucleotides in length, 2-5 nucleotides in length, 1-4 nucleotides in length, 2-4 nucleotides in length, 1-3 nucleotides in length, 2-3 nucleotides in length, or 1-2 nucleotides in length. In certain embodiments, the overhang regions can include extended overhang regions as provided above. The overhangs can be the result of one strand being longer than the other, or the result of two strands of the same length being staggered. The overhang can form a mismatch with the target mRNA or it can be complementary to the gene sequences being targeted or can be another sequence. The first and second strands can also be joined, e.g., by additional bases to form a hairpin, or by other non-base linkers. 
     In certain embodiments, the nucleotides in the overhang region of the dsRNAi agent can each independently be a modified or unmodified nucleotide including, but no limited to 2′-sugar modified, such as, 2′-F, 2′-O-methyl, thymidine (T), 2′-O-methoxyethyl-5-methyluridine (Teo), 2′-O-methoxyethyladenosine (Aeo), 2′-O-methoxyethyl-5-methylcytidine (m5Ceo), and any combinations thereof. For example, TT can be an overhang sequence for either end on either strand. The overhang can form a mismatch with the target mRNA or it can be complementary to the gene sequences being targeted or can be another sequence. 
     The 5′- or 3′-overhangs at the sense strand, antisense strand, or both strands of the dsRNAi agent may be phosphorylated. In some embodiments, the overhang region(s) contains two nucleotides having a phosphorothioate between the two nucleotides, where the two nucleotides can be the same or different. In some embodiments, the overhang is present at the 3′-end of the sense strand, antisense strand, or both strands. In some embodiments, this 3′-overhang is present in the antisense strand. In some embodiments, this 3′-overhang is present in the sense strand. 
     The dsRNAi agent may contain only a single overhang, which can strengthen the interference activity of the RNAi, without affecting its overall stability. For example, the single-stranded overhang may be located at the 3′-end of the sense strand or, alternatively, at the 3′-end of the antisense strand. The RNAi may also have a blunt end, located at the 5′-end of the antisense strand (or the 3′-end of the sense strand) or vice versa. Generally, the antisense strand of the dsRNAi agent has a nucleotide overhang at the 3′-end, and the 5′-end is blunt. While not wishing to be bound by theory, the asymmetric blunt end at the 5′-end of the antisense strand and 3′-end overhang of the antisense strand favor the guide strand loading into RISC process. 
     In certain embodiments, the dsRNAi agent is a double ended bluntmer of 19 nucleotides in length, wherein the sense strand contains at least one motif of three 2′-F modifications on three consecutive nucleotides at positions 7, 8, 9 from the 5′end. The antisense strand contains at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at positions 11, 12, 13 from the 5′end. 
     In other embodiments, the dsRNAi agent is a double ended bluntmer of 20 nucleotides in length, wherein the sense strand contains at least one motif of three 2′-F modifications on three consecutive nucleotides at positions 8, 9, 10 from the 5′end. The antisense strand contains at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at positions 11, 12, 13 from the 5′end. 
     In yet other embodiments, the dsRNAi agent is a double ended bluntmer of 21 nucleotides in length, wherein the sense strand contains at least one motif of three 2′-F modifications on three consecutive nucleotides at positions 9, 10, 11 from the 5′end. The antisense strand contains at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at positions 11, 12, 13 from the 5′end. 
     In certain embodiments, the dsRNAi agent comprises a 21 nucleotide sense strand and a 23 nucleotide antisense strand, wherein the sense strand contains at least one motif of three 2′-F modifications on three consecutive nucleotides at positions 9, 10, 11 from the 5′end; the antisense strand contains at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at positions 11, 12, 13 from the 5′end, wherein one end of the RNAi agent is blunt, while the other end comprises a 2 nucleotide overhang. Preferably, the 2 nucleotide overhang is at the 3′-end of the antisense strand. 
     When the 2 nucleotide overhang is at the 3′-end of the antisense strand, there may be two phosphorothioate internucleotide linkages between the terminal three nucleotides, wherein two of the three nucleotides are the overhang nucleotides, and the third nucleotide is a paired nucleotide next to the overhang nucleotide. In one embodiment, the RNAi agent additionally has two phosphorothioate internucleotide linkages between the terminal three nucleotides at both the 5′-end of the sense strand and at the 5′-end of the antisense strand. In certain embodiments, every nucleotide in the sense strand and the antisense strand of the dsRNAi agent, including the nucleotides that are part of the motifs are modified nucleotides. In certain embodiments each residue is independently modified with a 2′-O-methyl or 3′-fluoro, e.g., in an alternating motif. Optionally, the dsRNAi agent further comprises a ligand (preferably GalNAc3). 
     In certain embodiments, the dsRNAi agent comprises a sense and an antisense strand, wherein the sense strand is 25-30 nucleotide residues in length, wherein starting from the 5′ terminal nucleotide (position 1) positions 1 to 23 of the first strand comprise at least 8 ribonucleotides; the antisense strand is 36-66 nucleotide residues in length and, starting from the 3′ terminal nucleotide, comprises at least 8 ribonucleotides in the positions paired with positions 1-23 of sense strand to form a duplex; wherein at least the 3 ‘ terminal nucleotide of antisense strand is unpaired with sense strand, and up to 6 consecutive 3’ terminal nucleotides are unpaired with sense strand, thereby forming a 3′ single stranded overhang of 1-6 nucleotides; wherein the 5′-terminus of antisense strand comprises from 10-30 consecutive nucleotides which are unpaired with sense strand, thereby forming a 10-30 nucleotide single stranded 5′ overhang; wherein at least the sense strand 5′ terminal and 3′ terminal nucleotides are base paired with nucleotides of antisense strand when sense and antisense strands are aligned for maximum complementarity, thereby forming a substantially duplexed region between sense and antisense strands; and antisense strand is sufficiently complementary to a target RNA along at least 19 ribonucleotides of antisense strand length to reduce target gene expression when the double stranded nucleic acid is introduced into a mammalian cell; and wherein the sense strand contains at least one motif of three 2′-F modifications on three consecutive nucleotides, where at least one of the motifs occurs at or near the cleavage site. The antisense strand contains at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at or near the cleavage site. 
     In certain embodiments, the dsRNAi agent comprises sense and antisense strands, wherein the dsRNAi agent comprises a first strand having a length which is at least 25 and at most 29 nucleotides and a second strand having a length which is at most 30 nucleotides with at least one motif of three 2′-O-methyl modifications on three consecutive nucleotides at position 11, 12, 13 from the 5′ end; wherein the 3′ end of the first strand and the 5′ end of the second strand form a blunt end and the second strand is 1-4 nucleotides longer at its 3′ end than the first strand, wherein the duplex region region which is at least 25 nucleotides in length, and the second strand is sufficiently complementary to a target mRNA along at least 19 nucleotide of the second strand length to reduce target gene expression when the RNAi agent is introduced into a mammalian cell, and wherein Dicer cleavage of the dsRNAi agent preferentially results in an siRNA comprising the 3′-end of the second strand, thereby reducing expression of the target gene in the mammal. Optionally, the dsRNAi agent further comprises a ligand. 
     In certain embodiments, the sense strand of the dsRNAi agent contains at least one motif of three identical modifications on three consecutive nucleotides, where one of the motifs occurs at the cleavage site in the sense strand. 
     In certain embodiments, the antisense strand of the dsRNAi agent can also contain at least one motif of three identical modifications on three consecutive nucleotides, where one of the motifs occurs at or near the cleavage site in the antisense strand. 
     For a dsRNAi agent having a duplex region of 17-23 nucleotides in length, the cleavage site of the antisense strand is typically around the 10, 11, and 12 positions from the 5′-end. Thus the motifs of three identical modifications may occur at the 9, 10, 11 positions; the 10, 11, 12 positions; the 11, 12, 13 positions; the 12, 13, 14 positions; or the 13, 14, 15 positions of the antisense strand, the count starting from the first nucleotide from the 5′-end of the antisense strand, or, the count starting from the first paired nucleotide within the duplex region from the 5′-end of the antisense strand. The cleavage site in the antisense strand may also change according to the length of the duplex region of the dsRNAi agent from the 5′-end. 
     The sense strand of the dsRNAi agent may contain at least one motif of three identical modifications on three consecutive nucleotides at the cleavage site of the strand; and the antisense strand may have at least one motif of three identical modifications on three consecutive nucleotides at or near the cleavage site of the strand. When the sense strand and the antisense strand form a dsRNA duplex, the sense strand and the antisense strand can be so aligned that one motif of the three nucleotides on the sense strand and one motif of the three nucleotides on the antisense strand have at least one nucleotide overlap, i.e., at least one of the three nucleotides of the motif in the sense strand forms a base pair with at least one of the three nucleotides of the motif in the antisense strand. Alternatively, at least two nucleotides may overlap, or all three nucleotides may overlap. 
     In some embodiments, the sense strand of the dsRNAi agent may contain more than one motif of three identical modifications on three consecutive nucleotides. The first motif may occur at or near the cleavage site of the strand and the other motifs may be a wing modification. The term “wing modification” herein refers to a motif occurring at another portion of the strand that is separated from the motif at or near the cleavage site of the same strand. The wing modification is either adjacent to the first motif or is separated by at least one or more nucleotides. When the motifs are immediately adjacent to each other then the chemistries of the motifs are distinct from each other, and when the motifs are separated by one or more nucleotide than the chemistries can be the same or different. Two or more wing modifications may be present. For instance, when two wing modifications are present, each wing modification may occur at one end relative to the first motif which is at or near cleavage site or on either side of the lead motif. 
     Like the sense strand, the antisense strand of the dsRNAi agent may contain more than one motifs of three identical modifications on three consecutive nucleotides, with at least one of the motifs occurring at or near the cleavage site of the strand. This antisense strand may also contain one or more wing modifications in an alignment similar to the wing modifications that may be present on the sense strand. 
     In some embodiments, the wing modification on the sense strand or antisense strand of the dsRNAi agent typically does not include the first one or two terminal nucleotides at the 3′-end, 5′-end, or both ends of the strand. 
     In other embodiments, the wing modification on the sense strand or antisense strand of the dsRNAi agent typically does not include the first one or two paired nucleotides within the duplex region at the 3′-end, 5′-end, or both ends of the strand. 
     When the sense strand and the antisense strand of the dsRNAi agent each contain at least one wing modification, the wing modifications may fall on the same end of the duplex region, and have an overlap of one, two, or three nucleotides. 
     When the sense strand and the antisense strand of the dsRNAi agent each contain at least two wing modifications, the sense strand and the antisense strand can be so aligned that two modifications each from one strand fall on one end of the duplex region, having an overlap of one, two, or three nucleotides; two modifications each from one strand fall on the other end of the duplex region, having an overlap of one, two or three nucleotides; two modifications one strand fall on each side of the lead motif, having an overlap of one, two or three nucleotides in the duplex region. 
     In some embodiments, every nucleotide in the sense strand and antisense strand of the dsRNAi agent, including the nucleotides that are part of the motifs, may be modified. Each nucleotide may be modified with the same or different modification which can include one or more alteration of one or both of the non-linking phosphate oxygens or of one or more of the linking phosphate oxygens; alteration of a constituent of the ribose sugar, e.g., of the 2′-hydroxyl on the ribose sugar; wholesale replacement of the phosphate moiety with “dephospho” linkers; modification or replacement of a naturally occurring base; and replacement or modification of the ribose-phosphate backbone. 
     As nucleic acids are polymers of subunits, many of the modifications occur at a position which is repeated within a nucleic acid, e.g., a modification of a base, or a phosphate moiety, or a non-linking 0 of a phosphate moiety. In some cases the modification will occur at all of the subject positions in the nucleic acid but in many cases it will not. By way of example, a modification may only occur at a 3′- or 5′-terminal position, may only occur in a terminal region, e.g., at a position on a terminal nucleotide or in the last 2, 3, 4, 5, or 10 nucleotides of a strand. A modification may occur in a double strand region, a single strand region, or in both. A modification may occur only in the double strand region of a dsRNAi agent or may only occur in a single strand region of a dsRNAi agent. For example, a phosphorothioate modification at a non-linking 0 position may only occur at one or both ends, may only occur in a terminal region, e.g., at a position on a terminal nucleotide, or in the last 2, 3, 4, 5, or 10 nucleotides of a strand, or may occur in double strand and single strand regions, particularly at the ends. The 5′-end or ends can be phosphorylated. 
     It may be possible, e.g., to enhance stability, to include particular bases in overhangs, or to include modified nucleotides or nucleotide surrogates, in single strand overhangs, e.g., in a 5′- or 3′-overhang, or in both. For example, it can be desirable to include purine nucleotides in overhangs. In some embodiments all or some of the bases in a 3′- or 5′-overhang may be modified, e.g., with a modification described herein. Modifications can include, e.g., the use of modifications at the 2′ position of the ribose sugar with modifications that are known in the art, e.g., the use of deoxyribonucleotides, 2′-deoxy-2′-fluoro (2′-F) or 2′-O-methyl modified instead of the ribosugar of the nucleobase, and modifications in the phosphate group, e.g., phosphorothioate modifications. Overhangs need not be homologous with the target sequence. 
     In some embodiments, each residue of the sense strand and antisense strand is independently modified with LNA, CRN, cET, UNA, HNA, CeNA, 2′-methoxyethyl, 2′-O-methyl, 2′-O-allyl, 2′-C-allyl, 2′-deoxy, 2′-hydroxyl, or 2′-fluoro. The strands can contain more than one modification. In one embodiment, each residue of the sense strand and antisense strand is independently modified with 2′-O-methyl or 2′-fluoro. 
     At least two different modifications are typically present on the sense strand and antisense strand. Those two modifications may be the 2′-O-methyl or 2′-fluoro modifications, or others. 
     In certain embodiments, the N a  or N b  comprise modifications of an alternating pattern. The term “alternating motif” as used herein refers to a motif having one or more modifications, each modification occurring on alternating nucleotides of one strand. The alternating nucleotide may refer to one per every other nucleotide or one per every three nucleotides, or a similar pattern. For example, if A, B and C each represent one type of modification to the nucleotide, the alternating motif can be “ABABABABABAB . . . ,” “AABBAABBAABB . . . ,” “AABAABAABAAB . . . ,” “AAABAAABAAAB . . . ,” “AAABBBAAABBB . . . ,” or “ABCABCABCABC . . . ,” etc. 
     The type of modifications contained in the alternating motif may be the same or different. For example, if A, B, C, D each represent one type of modification on the nucleotide, the alternating pattern, i.e., modifications on every other nucleotide, may be the same, but each of the sense strand or antisense strand can be selected from several possibilities of modifications within the alternating motif such as “ABABAB . . . ”, “ACACAC . . . ” “BDBDBD . . . ” or “CDCDCD . . . ,” etc. 
     In some embodiments, the dsRNAi agent of the invention comprises the modification pattern for the alternating motif on the sense strand relative to the modification pattern for the alternating motif on the antisense strand is shifted. The shift may be such that the modified group of nucleotides of the sense strand corresponds to a differently modified group of nucleotides of the antisense strand and vice versa. For example, the sense strand when paired with the antisense strand in the dsRNA duplex, the alternating motif in the sense strand may start with “ABABAB” from 5′ to 3′ of the strand and the alternating motif in the antisense strand may start with “BABABA” from 5′ to 3′ of the strand within the duplex region. As another example, the alternating motif in the sense strand may start with “AABBAABB” from 5′ to 3′ of the strand and the alternating motif in the antisense strand may start with “BBAABBAA” from 5′ to 3′ of the strand within the duplex region, so that there is a complete or partial shift of the modification patterns between the sense strand and the antisense strand. 
     In some embodiments, the dsRNAi agent comprises the pattern of the alternating motif of 2′-O-methyl modification and 2′-F modification on the sense strand initially has a shift relative to the pattern of the alternating motif of 2′-O-methyl modification and 2′-F modification on the antisense strand initially, i.e., the 2′-O-methyl modified nucleotide on the sense strand base pairs with a 2′-F modified nucleotide on the antisense strand and vice versa. The 1 position of the sense strand may start with the 2′-F modification, and the 1 position of the antisense strand may start with the 2′-O-methyl modification. 
     The introduction of one or more motifs of three identical modifications on three consecutive nucleotides to the sense strand or antisense strand interrupts the initial modification pattern present in the sense strand or antisense strand. This interruption of the modification pattern of the sense or antisense strand by introducing one or more motifs of three identical modifications on three consecutive nucleotides to the sense or antisense strand may enhance the gene silencing activity against the target gene. 
     In some embodiments, when the motif of three identical modifications on three consecutive nucleotides is introduced to any of the strands, the modification of the nucleotide next to the motif is a different modification than the modification of the motif. For example, the portion of the sequence containing the motif is “ . . . N a YYYN b  . . . ,” where “Y” represents the modification of the motif of three identical modifications on three consecutive nucleotide, and “N a ” and “N b ” represent a modification to the nucleotide next to the motif “YYY” that is different than the modification of Y, and where N a  and N b  can be the same or different modifications. Alternatively, N a  or N b  may be present or absent when there is a wing modification present. 
     The iRNA may further comprise at least one phosphorothioate or methylphosphonate internucleotide linkage. The phosphorothioate or methylphosphonate internucleotide linkage modification may occur on any nucleotide of the sense strand, antisense strand, or both strands in any position of the strand. For instance, the internucleotide linkage modification may occur on every nucleotide on the sense strand or antisense strand; each internucleotide linkage modification may occur in an alternating pattern on the sense strand or antisense strand; or the sense strand or antisense strand may contain both internucleotide linkage modifications in an alternating pattern. The alternating pattern of the internucleotide linkage modification on the sense strand may be the same or different from the antisense strand, and the alternating pattern of the internucleotide linkage modification on the sense strand may have a shift relative to the alternating pattern of the internucleotide linkage modification on the antisense strand. In one embodiment, a double-stranded RNAi agent comprises 6-8 phosphorothioate internucleotide linkages. In some embodiments, the antisense strand comprises two phosphorothioate internucleotide linkages at the 5′-end and two phosphorothioate internucleotide linkages at the 3′-end, and the sense strand comprises at least two phosphorothioate internucleotide linkages at either the 5′-end or the 3′-end. 
     In some embodiments, the dsRNAi agent comprises a phosphorothioate or methylphosphonate internucleotide linkage modification in the overhang region. For example, the overhang region may contain two nucleotides having a phosphorothioate or methylphosphonate internucleotide linkage between the two nucleotides. Internucleotide linkage modifications also may be made to link the overhang nucleotides with the terminal paired nucleotides within the duplex region. For example, at least 2, 3, 4, or all the overhang nucleotides may be linked through phosphorothioate or methylphosphonate internucleotide linkage, and optionally, there may be additional phosphorothioate or methylphosphonate internucleotide linkages linking the overhang nucleotide with a paired nucleotide that is next to the overhang nucleotide. For instance, there may be at least two phosphorothioate internucleotide linkages between the terminal three nucleotides, in which two of the three nucleotides are overhang nucleotides, and the third is a paired nucleotide next to the overhang nucleotide. These terminal three nucleotides may be at the 3′-end of the antisense strand, the 3′-end of the sense strand, the 5′-end of the antisense strand, or the 5′end of the antisense strand. 
     In some embodiments, the 2-nucleotide overhang is at the 3′-end of the antisense strand, and there are two phosphorothioate internucleotide linkages between the terminal three nucleotides, wherein two of the three nucleotides are the overhang nucleotides, and the third nucleotide is a paired nucleotide next to the overhang nucleotide. Optionally, the dsRNAi agent may additionally have two phosphorothioate internucleotide linkages between the terminal three nucleotides at both the 5′-end of the sense strand and at the 5′-end of the antisense strand. 
     In one embodiment, the dsRNAi agent comprises mismatch(es) with the target, within the duplex, or combinations thereof. The mismatch may occur in the overhang region or the duplex region. The base pair may be ranked on the basis of their propensity to promote dissociation or melting (e.g., on the free energy of association or dissociation of a particular pairing, the simplest approach is to examine the pairs on an individual pair basis, though next neighbor or similar analysis can also be used). In terms of promoting dissociation: A:U is preferred over G:C; G:U is preferred over G:C; and I:C is preferred over G:C (I=inosine). Mismatches, e.g., non-canonical or other than canonical pairings (as described elsewhere herein) are preferred over canonical (A:T, A:U, G:C) pairings; and pairings which include a universal base are preferred over canonical pairings. 
     In certain embodiments, the dsRNAi agent comprises at least one of the first 1, 2, 3, 4, or 5 base pairs within the duplex regions from the 5′-end of the antisense strand independently selected from the group of: A:U, G:U, I:C, and mismatched pairs, e.g., non-canonical or other than canonical pairings or pairings which include a universal base, to promote the dissociation of the antisense strand at the 5′-end of the duplex. 
     In certain embodiments, the nucleotide at the 1 position within the duplex region from the 5′-end in the antisense strand is selected from A, dA, dU, U, and dT. Alternatively, at least one of the first 1, 2, or 3 base pair within the duplex region from the 5′-end of the antisense strand is an AU base pair. For example, the first base pair within the duplex region from the 5′-end of the antisense strand is an AU base pair. 
     In other embodiments, the nucleotide at the 3′-end of the sense strand is deoxy-thymine (dT) or the nucleotide at the 3′-end of the antisense strand is deoxy-thymine (dT). For example, there is a short sequence of deoxy-thymine nucleotides, for example, two dT nucleotides on the 3′-end of the sense, antisense strand, or both strands. 
     In certain embodiments, the sense strand sequence may be represented by formula (I): 
       5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′  (I)
 
     wherein: 
     i and j are each independently 0 or 1; 
     p and q are each independently 0-6; 
     each N a  independently represents an oligonucleotide sequence comprising 0-25 modified nucleotides, each sequence comprising at least two differently modified nucleotides; 
     each N b  independently represents an oligonucleotide sequence comprising 0-10 modified nucleotides; 
     each n p  and n q  independently represent an overhang nucleotide; 
     wherein N b  and Y do not have the same modification; and 
     XXX, YYY, and ZZZ each independently represent one motif of three identical modifications on three consecutive nucleotides. Preferably YYY is all 2′-F modified nucleotides. 
     In some embodiments, the N a  or N b  comprises modifications of alternating pattern. 
     In some embodiments, the YYY motif occurs at or near the cleavage site of the sense strand. For example, when the dsRNAi agent has a duplex region of 17-23 nucleotides in length, the YYY motif can occur at or the vicinity of the cleavage site (e.g.: can occur at positions 6, 7, 8; 7, 8, 9; 8, 9, 10; 9, 10, 11; 10, 11, 12; or 11, 12, 13) of the sense strand, the count starting from the first nucleotide, from the 5′-end; or optionally, the count starting at the first paired nucleotide within the duplex region, from the 5′-end. 
     In one embodiment, i is 1 and j is 0, or i is 0 and j is 1, or both i and j are 1. The sense strand can therefore be represented by the following formulas: 
       5′ n   p -N a -YYY-N b -ZZZ-N a - n   q 3′  (Ib);
 
       5′ n   p -N a -XXX-N b -YYY-N a - n   q 3′  (Ic); or
 
       5′ n   p -N a -XXX-N b -YYY-N b -ZZZ-N a - n   q 3′  (Id).
 
     When the sense strand is represented by formula (Ib), N b  represents an oligonucleotide sequence comprising 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a  independently can represent an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the sense strand is represented as formula (Ic), N b  represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a  can independently represent an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the sense strand is represented as formula (Id), each N b  independently represents an oligonucleotide sequence comprising 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Preferably, N b  is 0, 1, 2, 3, 4, 5, or 6 Each N a  can independently represent an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     Each of X, Y and Z may be the same or different from each other. 
     In other embodiments, i is 0 and j is 0, and the sense strand may be represented by the formula: 
       5′ n   p -N a -YYY-N a - n   q 3′  (Ia).
 
     When the sense strand is represented by formula (Ia), each N a  independently can represent an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     In one embodiment, the antisense strand sequence of the RNAi may be represented by formula (II): 
       5′ n   q′ -N a ′-(Z′Z′Z′) k —N b ′-Y′Y′Y′-N b ′-(X′X′X′) l -N a ′- n   p ′3′  (II)
 
     wherein: 
     k and 1 are each independently 0 or 1; 
     p′ and q′ are each independently 0-6; 
     each N a ′ independently represents an oligonucleotide sequence comprising 0-25 modified nucleotides, each sequence comprising at least two differently modified nucleotides; 
     each N b ′ independently represents an oligonucleotide sequence comprising 0-10 modified nucleotides; 
     each n p ′ and n q ′ independently represent an overhang nucleotide; 
     wherein N b ′ and Y′ do not have the same modification; and 
     X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides. 
     In some embodiments, the N a ′ or N b ′ comprises modifications of alternating pattern. 
     The Y′Y′Y′ motif occurs at or near the cleavage site of the antisense strand. For example, when the dsRNAi agent has a duplex region of 17-23 nucleotides in length, the Y′Y′Y′ motif can occur at positions 9, 10, 11; 10, 11, 12; 11, 12, 13; 12, 13, 14; or 13, 14, 15 of the antisense strand, with the count starting from the first nucleotide, from the 5′-end; or optionally, the count starting at the first paired nucleotide within the duplex region, from the 5′-end. Preferably, the Y′Y′Y′ motif occurs at positions 11, 12, 13. 
     In certain embodiments, Y′Y′Y′ motif is all 2′-OMe modified nucleotides. 
     In certain embodiments, k is 1 and 1 is 0, or k is 0 and 1 is 1, or both k and 1 are 1. 
     The antisense strand can therefore be represented by the following formulas: 
       5′ n   q′ -N a ′-Z′Z′Z′—N b ′-Y′Y′Y′-N a ′- n   p′ 3′  (IIb);
 
       5′ n   q′ -N a ′-Y′Y′Y′-N b ′-X′X′X′- n   p′ 3′  (IIc); or
 
       5′ n   q′ -N a ′-Z′Z′Z′-N b ′-Y′Y′Y′-N b ′-X′X′X′-N a ′- n   p′ 3′  (IId).
 
     When the antisense strand is represented by formula (IIb), N b ′ represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a ′ independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the antisense strand is represented as formula (IIc), N b ′ represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a ′ independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the antisense strand is represented as formula (IId), each N b ′ independently represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a ′ independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. Preferably, N b  is 0, 1, 2, 3, 4, 5, or 6. 
     In other embodiments, k is 0 and 1 is 0 and the antisense strand may be represented by the formula: 
       5′ n   p′ -N a′ -Y′Y′Y′-N a′ - n   q′ 3′  (Ia).
 
     When the antisense strand is represented as formula (IIa), each N a ′ independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. Each of X′, Y′ and Z′ may be the same or different from each other. 
     Each nucleotide of the sense strand and antisense strand may be independently modified with LNA, CRN, UNA, cEt, HNA, CeNA, 2′-methoxyethyl, 2′-O-allyl, 2′-C-allyl, 2′-hydroxyl, or 2′-fluoro. For example, each nucleotide of the sense strand and antisense strand is independently modified with 2′-O-methyl or 2′-fluoro. Each X, Y, Z, X′, Y′, and Z′, in particular, may represent a 2′-O-methyl modification or a 2′-fluoro modification. 
     In some embodiments, the sense strand of the dsRNAi agent may contain YYY motif occurring at 9, 10, and 11 positions of the strand when the duplex region is 21 nt, the count starting from the first nucleotide from the 5′-end, or optionally, the count starting at the first paired nucleotide within the duplex region, from the 5′-end; and Y represents 2′-F modification. The sense strand may additionally contain XXX motif or ZZZ motifs as wing modifications at the opposite end of the duplex region; and XXX and ZZZ each independently represents a 2′-OMe modification or 2′-F modification. 
     In some embodiments the antisense strand may contain Y′Y′Y′ motif occurring at positions 11, 12, 13 of the strand, the count starting from the first nucleotide from the 5′-end, or optionally, the count starting at the first paired nucleotide within the duplex region, from the 5′-end; and Y′ represents 2′-O-methyl modification. The antisense strand may additionally contain X′X′X′ motif or Z′Z′Z′ motifs as wing modifications at the opposite end of the duplex region; and X′X′X′ and Z′Z′Z′ each independently represents a 2′-OMe modification or 2′-F modification. 
     The sense strand represented by any one of the above formulas (Ia), (Ib), (Ic), and (Id) forms a duplex with a antisense strand being represented by any one of formulas (IIa), (IIb), (IIc), and (IId), respectively. 
     Accordingly, the dsRNAi agents for use in the methods of the invention may comprise a sense strand and an antisense strand, each strand having 14 to 30 nucleotides, the iRNA duplex represented by formula (III): 
       sense: 5′ n   p -N a -(XXX) i -N b -YYY-N b -(ZZZ) j -N a - n   q 3′
 
       antisense: 3′  n   p ′-N a ′-(X′X′X′) k -N b ′-Y′Y′Y′-N b ′-(Z′Z′Z′) l -N a ′- n   q ′5′  (III)
 
     wherein: 
     j, k, and 1 are each independently 0 or 1; 
     p, p′, q, and q′ are each independently 0-6; 
     each N a  and N a ′ independently represents an oligonucleotide sequence comprising 0-25 modified nucleotides, each sequence comprising at least two differently modified nucleotides; 
     each N b  and N b ′ independently represents an oligonucleotide sequence comprising 0-10 modified nucleotides; 
     wherein each n p ′, n p , n q ′, and n q , each of which may or may not be present, independently represents an overhang nucleotide; and 
     XXX, YYY, ZZZ, X′X′X′, Y′Y′Y′, and Z′Z′Z′ each independently represent one motif of three identical modifications on three consecutive nucleotides. 
     In one embodiment, i is 0 and j is 0; or i is 1 and j is 0; or i is 0 and j is 1; or both i and j are 0; or both i and j are 1. In another embodiment, k is 0 and 1 is 0; or k is 1 and 1 is 0; k is 0 and 1 is 1; or both k and 1 are 0; or both k and 1 are 1. 
     Exemplary combinations of the sense strand and antisense strand forming an iRNA duplex include the formulas below: 
       5′ n   p -N a -YYY-N a - n   q 3′
 
       3′ n   p ′-N a ′-Y′Y′Y′-N a   ′n   q ′5′  (IIIa)
 
       5′ n   p -N a -YYY-N b -ZZZ-N a - n   q 3′
 
       3′ n   p ′-N a ′-Y′Y′Y′-N b ′-Z′Z′Z′-N a   ′n   q ′5′  (IIIb)
 
       5′ n   p -N a -XXX-N b -YYY-N a - n   q 3′
 
       3′  n   p ′-N a ′-X′X′X′-N b ′-Y′Y′Y′-N a ′- n   q ′5′  (IIIc)
 
       5′ n   p -N a -XXX-N b -YYY-N b -ZZZ-N a - n   q 3′
 
       3′ n   p ′-N a ′-X′X′X′-N b ′-Y′Y′Y′-N b ′-Z′Z′Z′-N a - n   q ′5′  (IIId)
 
     When the dsRNAi agent is represented by formula (IIIa), each N a  independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the dsRNAi agent is represented by formula (IIIb), each N b  independently represents an oligonucleotide sequence comprising 1-10, 1-7, 1-5, or 1-4 modified nucleotides. Each N a  independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the dsRNAi agent is represented as formula (IIIc), each N b , N b ′ independently represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a  independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. 
     When the dsRNAi agent is represented as formula (IIId), each N b , N b ′ independently represents an oligonucleotide sequence comprising 0-10, 0-7, 0-10, 0-7, 0-5, 0-4, 0-2, or 0 modified nucleotides. Each N a , N a ′ independently represents an oligonucleotide sequence comprising 2-20, 2-15, or 2-10 modified nucleotides. Each of N a , N a ′, N b , and N b ′ independently comprises modifications of alternating pattern. 
     Each of X, Y, and Z in formulas (III), (IIIa), (IIIb), (IIIc), and (IIId) may be the same or different from each other. 
     When the dsRNAi agent is represented by formula (III), (IIIa), (IIIb), (IIIc), and (IIId), at least one of the Y nucleotides may form a base pair with one of the Y′ nucleotides. Alternatively, at least two of the Y nucleotides form base pairs with the corresponding Y′ nucleotides; or all three of the Y nucleotides all form base pairs with the corresponding Y′ nucleotides. 
     When the dsRNAi agent is represented by formula (IIIb) or (IIId), at least one of the Z nucleotides may form a base pair with one of the Z′ nucleotides. Alternatively, at least two of the Z nucleotides form base pairs with the corresponding Z′ nucleotides; or all three of the Z nucleotides all form base pairs with the corresponding Z′ nucleotides. 
     When the dsRNAi agent is represented as formula (IIIc) or (IIId), at least one of the X nucleotides may form a base pair with one of the X′ nucleotides. Alternatively, at least two of the X nucleotides form base pairs with the corresponding X′ nucleotides; or all three of the X nucleotides all form base pairs with the corresponding X′ nucleotides. 
     In certain embodiments, the modification on the Y nucleotide is different than the modification on the Y′ nucleotide, the modification on the Z nucleotide is different than the modification on the Z′ nucleotide, and/or the modification on the X nucleotide is different than the modification on the X′ nucleotide. 
     In certain embodiments, when the dsRNAi agent is represented by formula (IIId), the N a  modifications are 2′-O-methyl or 2′-fluoro modifications. In other embodiments, when the RNAi agent is represented by formula (IIId), the N a  modifications are 2′-O-methyl or 2′-fluoro modifications and n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide a via phosphorothioate linkage. In yet other embodiments, when the RNAi agent is represented by formula (IIId), the N a  modifications are 2′-O-methyl or 2′-fluoro modifications, n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via phosphorothioate linkage, and the sense strand is conjugated to one or more GalNAc derivatives attached through a bivalent or trivalent branched linker (described below). In other embodiments, when the RNAi agent is represented by formula (IIId), the N a  modifications are 2′-O-methyl or 2′-fluoro modifications, n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via phosphorothioate linkage, the sense strand comprises at least one phosphorothioate linkage, and the sense strand is conjugated to one or more GalNAc derivatives attached through a bivalent or trivalent branched linker. 
     In some embodiments, when the dsRNAi agent is represented by formula (IIIa), the N a  modifications are 2′-O-methyl or 2′-fluoro modifications, n p ′&gt;0 and at least one n p ′ is linked to a neighboring nucleotide via phosphorothioate linkage, the sense strand comprises at least one phosphorothioate linkage, and the sense strand is conjugated to one or more GalNAc derivatives attached through a bivalent or trivalent branched linker. 
     In some embodiments, the dsRNAi agent is a multimer containing at least two duplexes represented by formula (III), (IIIa), (IIIb), (IIIc), and (IIId), wherein the duplexes are connected by a linker. The linker can be cleavable or non-cleavable. Optionally, the multimer further comprises a ligand. Each of the duplexes can target the same gene or two different genes; or each of the duplexes can target same gene at two different target sites. 
     In some embodiments, the dsRNAi agent is a multimer containing three, four, five, six, or more duplexes represented by formula (III), (IIIa), (IIIb), (IIIc), and (IIId), wherein the duplexes are connected by a linker. The linker can be cleavable or non-cleavable. Optionally, the multimer further comprises a ligand. Each of the duplexes can target the same gene or two different genes; or each of the duplexes can target same gene at two different target sites. 
     In one embodiment, two dsRNAi agents represented by at least one of formulas (III), (IIIa), (IIIb), (IIIc), and (IIId) are linked to each other at the 5′ end, and one or both of the 3′ ends, and are optionally conjugated to to a ligand. Each of the agents can target the same gene or two different genes; or each of the agents can target same gene at two different target sites. 
     Various publications describe multimeric iRNAs that can be used in the methods of the invention. Such publications include U.S. Pat. No. 7,858,769, WO2007/091269, WO2010/141511, WO2007/117686, WO2009/014887, and WO2011/031520 the entire contents of each of which are hereby incorporated herein by reference. 
     As described in more detail below, the iRNA that contains conjugations of one or more carbohydrate moieties to an iRNA can optimize one or more properties of the iRNA. In many cases, the carbohydrate moiety will be attached to a modified subunit of the iRNA. For example, the ribose sugar of one or more ribonucleotide subunits of a iRNA can be replaced with another moiety, e.g., a non-carbohydrate (preferably cyclic) carrier to which is attached a carbohydrate ligand. A ribonucleotide subunit in which the ribose sugar of the subunit has been so replaced is referred to herein as a ribose replacement modification subunit (RRMS). A cyclic carrier may be a carbocyclic ring system, i.e., all ring atoms are carbon atoms, or a heterocyclic ring system, i.e., one or more ring atoms may be a heteroatom, e.g., nitrogen, oxygen, sulfur. The cyclic carrier may be a monocyclic ring system, or may contain two or more rings, e.g. fused rings. The cyclic carrier may be a fully saturated ring system, or it may contain one or more double bonds. 
     The ligand may be attached to the polynucleotide via a carrier. The carriers include (i) at least one “backbone attachment point,” preferably two “backbone attachment points” and (ii) at least one “tethering attachment point.” A “backbone attachment point” as used herein refers to a functional group, e.g. a hydroxyl group, or generally, a bond available for, and that is suitable for incorporation of the carrier into the backbone, e.g., the phosphate, or modified phosphate, e.g., sulfur containing, backbone, of a ribonucleic acid. A “tethering attachment point” (TAP) in some embodiments refers to a constituent ring atom of the cyclic carrier, e.g., a carbon atom or a heteroatom (distinct from an atom which provides a backbone attachment point), that connects a selected moiety. The moiety can be, e.g., a carbohydrate, e.g. monosaccharide, disaccharide, trisaccharide, tetrasaccharide, oligosaccharide, or polysaccharide. Optionally, the selected moiety is connected by an intervening tether to the cyclic carrier. Thus, the cyclic carrier will often include a functional group, e.g., an amino group, or generally, provide a bond, that is suitable for incorporation or tethering of another chemical entity, e.g., a ligand to the constituent ring. 
     The iRNA may be conjugated to a ligand via a carrier, wherein the carrier can be cyclic group or acyclic group; preferably, the cyclic group is selected from pyrrolidinyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, [1,3]dioxolane, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl, quinoxalinyl, pyridazinonyl, tetrahydrofuryl, and decalin; preferably, the acyclic group is a serinol backbone or diethanolamine backbone. 
     In certain embodiments, the iRNA is an agent selected from agents listed in Table 3 and Table 5. In one embodiment, the iRNA agent targets nucleotides 3221-3243 of SEQ ID NO:1. In one embodiment, the RNAi agent is AD-67635 (targeting nucleotides 3224-3243 of SEQ ID NO:1). In another embodiment, the RNAi agent is AD-67637 (targeting nucleotides 3223-3242 of SEQ ID NO:1). These agents may further comprise a ligand. 
     III. iRNAs Conjugated to Ligands 
     Another modification of the RNA of an iRNA of the invention involves chemically linking to the iRNA one or more ligands, moieties or conjugates that enhance the activity, cellular distribution, or cellular uptake of the iRNA e.g., into a cell. Such moieties include but are not limited to lipid moieties such as a cholesterol moiety (Letsinger et al.,  Proc. Natl. Acid. Sci. USA,  1989, 86: 6553-6556), cholic acid (Manoharan et al.,  Biorg. Med. Chem. Let.,  1994, 4:1053-1060). In certain embodiments, the modification can include a thioether, e.g., beryl-S-tritylthiol (Manoharan et al.,  Ann. N.Y. Acad. Sci.,  1992, 660:306-309; Manoharan et al.,  Biorg. Med. Chem. Let.,  1993, 3:2765-2770), a thiocholesterol (Oberhauser et al.,  Nucl. Acids Res.,  1992, 20:533-538), an aliphatic chain, e.g., dodecandiol or undecyl residues (Saison-Behmoaras et al.,  EMBO J,  1991, 10:1111-1118; Kabanov et al.,  FEBS Lett.,  1990, 259:327-330; Svinarchuk et al.,  Biochimie,  1993, 75:49-54), a phospholipid, e.g., di-hexadecyl-rac-glycerol or triethyl-ammonium 1,2-di-O-hexadecyl-rac-glycero-3-phosphonate (Manoharan et al.,  Tetrahedron Lett.,  1995, 36:3651-3654; Shea et al.,  Nucl. Acids Res.,  1990, 18:3777-3783), a polyamine or a polyethylene glycol chain (Manoharan et al.,  Nucleosides  &amp;  Nucleotides,  1995, 14:969-973), or adamantane acetic acid (Manoharan et al.,  Tetrahedron Lett.,  1995, 36:3651-3654), a palmityl moiety (Mishra et al.,  Biochim. Biophys. Acta,  1995, 1264:229-237), or an octadecylamine or hexylamino-carbonyloxycholesterol moiety (Crooke et al.,  J. Pharmacol. Exp. Ther.,  1996, 277:923-937). 
     In certain embodiments, a ligand alters the distribution, targeting or lifetime of an iRNA agent into which it is incorporated. In preferred embodiments a ligand provides an enhanced affinity for a selected target, e.g., molecule, cell or cell type, compartment, e.g., a cellular or organ compartment, tissue, organ or region of the body, as, e.g., compared to a species absent such a ligand. Preferred ligands do not take part in duplex pairing in a duplexed nucleic acid. 
     Ligands can include a naturally occurring substance, such as a protein (e.g., human serum albumin (HSA), low-density lipoprotein (LDL), or globulin); carbohydrate (e.g., a dextran, pullulan, chitin, chitosan, inulin, cyclodextrin, N-acetylgalactosamine, or hyaluronic acid); or a lipid. The ligand can also be a recombinant or synthetic molecule, such as a synthetic polymer, e.g., a synthetic polyamino acid. Examples of polyamino acids include polyamino acid is a polylysine (PLL), poly L-aspartic acid, poly L-glutamic acid, styrene-maleic acid anhydride copolymer, poly(L-lactide-co-glycolied) copolymer, divinyl ether-maleic anhydride copolymer, N-(2-hydroxypropyl)methacrylamide copolymer (HMPA), polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyurethane, poly(2-ethylacryllic acid), N-isopropylacrylamide polymers, or polyphosphazine Example of polyamines include: polyethylenimine, polylysine (PLL), spermine, spermidine, polyamine, pseudopeptide-polyamine, peptidomimetic polyamine, dendrimer polyamine, arginine, amidine, protamine, cationic lipid, cationic porphyrin, quaternary salt of a polyamine, or an alpha helical peptide. 
     Ligands can also include targeting groups, e.g., a cell or tissue targeting agent, e.g., a lectin, glycoprotein, lipid or protein, e.g., an antibody, that binds to a specified cell type such as a kidney cell. A targeting group can be a thyrotropin, melanotropin, lectin, glycoprotein, surfactant protein A, Mucin carbohydrate, multivalent lactose, multivalent galactose, monovalent or multivalent N-acetyl-galactosamine, N-acetyl-gulucoseamine multivalent mannose, multivalent fucose, glycosylated polyaminoacids, multivalent galactose, transferrin, bisphosphonate, polyglutamate, polyaspartate, a lipid, cholesterol, a steroid, bile acid, folate, vitamin B12, vitamin A, biotin, or an RGD peptide or RGD peptide mimetic. In certain embodiments, the ligand is monovalent or multivalent N-acetyl-galactosamine. In certain embodiments, the ligand is cholesterol. 
     Other examples of ligands include dyes, intercalating agents (e.g. acridines), cross-linkers (e.g. psoralene, mitomycin C), porphyrins (TPPC4, texaphyrin, Sapphyrin), polycyclic aromatic hydrocarbons (e.g., phenazine, dihydrophenazine), artificial endonucleases (e.g. EDTA), lipophilic molecules, e.g., cholesterol, cholic acid, adamantane acetic acid, 1-pyrene butyric acid, dihydrotestosterone, 1,3-Bis-O(hexadecyl)glycerol, geranyloxyhexyl group, hexadecylglycerol, borneol, menthol, 1,3-propanediol, heptadecyl group, palmitic acid, myristic acid, O3-(oleoyl)lithocholic acid, O3-(oleoyl)cholenic acid, dimethoxytrityl, or phenoxazine) and peptide conjugates (e.g., antennapedia peptide, Tat peptide), alkylating agents, phosphate, amino, mercapto, PEG (e.g., PEG-40K), MPEG, [MPEG] 2 , polyamino, alkyl, substituted alkyl, radiolabeled markers, enzymes, haptens (e.g. biotin), transport/absorption facilitators (e.g., aspirin, vitamin E, folic acid), synthetic ribonucleases (e.g., imidazole, bisimidazole, histamine, imidazole clusters, acridine-imidazole conjugates, Eu3+ complexes of tetraazamacrocycles), dinitrophenyl, HRP, or AP. 
     Ligands can be proteins, e.g., glycoproteins, or peptides, e.g., molecules having a specific affinity for a co-ligand, or antibodies e.g., an antibody, that binds to a specified cell type such as a hepatic cell. Ligands can also include hormones and hormone receptors. They can also include non-peptidic species, such as lipids, lectins, carbohydrates, vitamins, cofactors, multivalent lactose, multivalent galactose, N-acetyl-galactosamine, N-acetyl-gulucosamine multivalent mannose, or multivalent fucose. The ligand can be, for example, a lipopolysaccharide, an activator of p38 MAP kinase, or an activator of NF-κB. 
     The ligand can be a substance, e.g., a drug, which can increase the uptake of the iRNA agent into the cell, for example, by disrupting the cell&#39;s cytoskeleton, e.g., by disrupting the cell&#39;s microtubules, microfilaments, or intermediate filaments. The drug can be, for example, taxon, vincristine, vinblastine, cytochalasin, nocodazole, japlakinolide, latrunculin A, phalloidin, swinholide A, indanocine, or myoservin. 
     In some embodiments, a ligand attached to an iRNA as described herein acts as a pharmacokinetic modulator (PK modulator). PK modulators include lipophiles, bile acids, steroids, phospholipid analogues, peptides, protein binding agents, PEG, vitamins etc. Exemplary PK modulators include, but are not limited to, cholesterol, fatty acids, cholic acid, lithocholic acid, dialkylglycerides, diacylglyceride, phospholipids, sphingolipids, naproxen, ibuprofen, vitamin E, biotin etc. Oligonucleotides that comprise a number of phosphorothioate linkages are also known to bind to serum protein, thus short oligonucleotides, e.g., oligonucleotides of about 5 bases, 10 bases, 15 bases, or 20 bases, comprising multiple of phosphorothioate linkages in the backbone are also amenable to the present invention as ligands (e.g. as PK modulating ligands). In addition, aptamers that bind serum components (e.g. serum proteins) are also suitable for use as PK modulating ligands in the embodiments described herein. 
     Ligand-conjugated iRNAs of the invention may be synthesized by the use of an oligonucleotide that bears a pendant reactive functionality, such as that derived from the attachment of a linking molecule onto the oligonucleotide (described below). This reactive oligonucleotide may be reacted directly with commercially-available ligands, ligands that are synthesized bearing any of a variety of protecting groups, or ligands that have a linking moiety attached thereto. 
     The oligonucleotides used in the conjugates of the present invention may be conveniently and routinely made through the well-known technique of solid-phase synthesis. Equipment for such synthesis is sold by several vendors including, for example, Applied Biosystems (Foster City, Calif.). Any other means for such synthesis known in the art may additionally or alternatively be employed. It is also known to use similar techniques to prepare other oligonucleotides, such as the phosphorothioates and alkylated derivatives. 
     In the ligand-conjugated iRNAs and ligand-molecule bearing sequence-specific linked nucleosides of the present invention, the oligonucleotides and oligonucleosides may be assembled on a suitable DNA synthesizer utilizing standard nucleotide or nucleoside precursors, or nucleotide or nucleoside conjugate precursors that already bear the linking moiety, ligand-nucleotide or nucleoside-conjugate precursors that already bear the ligand molecule, or non-nucleoside ligand-bearing building blocks. 
     When using nucleotide-conjugate precursors that already bear a linking moiety, the synthesis of the sequence-specific linked nucleosides is typically completed, and the ligand molecule is then reacted with the linking moiety to form the ligand-conjugated oligonucleotide. In some embodiments, the oligonucleotides or linked nucleosides of the present invention are synthesized by an automated synthesizer using phosphoramidites derived from ligand-nucleoside conjugates in addition to the standard phosphoramidites and non-standard phosphoramidites that are commercially available and routinely used in oligonucleotide synthesis. 
     A. Lipid Conjugates 
     In certain embodiments, the ligand or conjugate is a lipid or lipid-based molecule. Such a lipid or lipid-based molecule preferably binds a serum protein, e.g., human serum albumin (HSA). An HSA binding ligand allows for distribution of the conjugate to a target tissue, e.g., a non-kidney target tissue of the body. For example, the target tissue can be the liver, including parenchymal cells of the liver. Other molecules that can bind HSA can also be used as ligands. For example, naproxen or aspirin can be used. A lipid or lipid-based ligand can (a) increase resistance to degradation of the conjugate, (b) increase targeting or transport into a target cell or cell membrane, or (c) can be used to adjust binding to a serum protein, e.g., HSA. 
     A lipid based ligand can be used to inhibit, e.g., control the binding of the conjugate to a target tissue. For example, a lipid or lipid-based ligand that binds to HSA more strongly will be less likely to be targeted to the kidney and therefore less likely to be cleared from the body. A lipid or lipid-based ligand that binds to HSA less strongly can be used to target the conjugate to the kidney. 
     In certain embodiments, the lipid based ligand binds HSA. Preferably, it binds HSA with a sufficient affinity such that the conjugate will be preferably distributed to a non-kidney tissue. However, it is preferred that the affinity not be so strong that the HSA-ligand binding cannot be reversed. 
     In other embodiments, the lipid based ligand binds HSA weakly or not at all, such that the conjugate will be preferably distributed to the kidney. Other moieties that target to kidney cells can also be used in place of, or in addition to, the lipid based ligand. 
     In another aspect, the ligand is a moiety, e.g., a vitamin, which is taken up by a target cell, e.g., a proliferating cell. These are particularly useful for treating disorders characterized by unwanted cell proliferation, e.g., of the malignant or non-malignant type, e.g., cancer cells. Exemplary vitamins include vitamin A, E, and K. Other exemplary vitamins include are B vitamin, e.g., folic acid, B12, riboflavin, biotin, pyridoxal or other vitamins or nutrients taken up by target cells such as liver cells. Also included are HSA and low density lipoprotein (LDL). 
     B. Cell Permeation Agents 
     In another aspect, the ligand is a cell-permeation agent, preferably a helical cell-permeation agent. Preferably, the agent is amphipathic. An exemplary agent is a peptide such as tat or antennopedia. If the agent is a peptide, it can be modified, including a peptidylmimetic, invertomers, non-peptide or pseudo-peptide linkages, and use of D-amino acids. The helical agent is preferably an alpha-helical agent, which preferably has a lipophilic and a lipophobic phase. 
     The ligand can be a peptide or peptidomimetic. A peptidomimetic (also referred to herein as an oligopeptidomimetic) is a molecule capable of folding into a defined three-dimensional structure similar to a natural peptide. The attachment of peptide and peptidomimetics to iRNA agents can affect pharmacokinetic distribution of the iRNA, such as by enhancing cellular recognition and absorption. The peptide or peptidomimetic moiety can be about 5-50 amino acids long, e.g., about 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 amino acids long. 
     A peptide or peptidomimetic can be, for example, a cell permeation peptide, cationic peptide, amphipathic peptide, or hydrophobic peptide (e.g., consisting primarily of Tyr, Trp, or Phe). The peptide moiety can be a dendrimer peptide, constrained peptide or crosslinked peptide. In another alternative, the peptide moiety can include a hydrophobic membrane translocation sequence (MTS). An exemplary hydrophobic MTS-containing peptide is RFGF having the amino acid sequence AAVALLPAVLLALLAP (SEQ ID NO: 14). An RFGF analogue (e.g., amino acid sequence AALLPVLLAAP (SEQ ID NO:15) containing a hydrophobic MTS can also be a targeting moiety. The peptide moiety can be a “delivery” peptide, which can carry large polar molecules including peptides, oligonucleotides, and protein across cell membranes. For example, sequences from the HIV Tat protein (GRKKRRQRRRPPQ (SEQ ID NO:16) and the  Drosophila  Antennapedia protein (RQIKIWFQNRRMKWKK (SEQ ID NO:17) have been found to be capable of functioning as delivery peptides. A peptide or peptidomimetic can be encoded by a random sequence of DNA, such as a peptide identified from a phage-display library, or one-bead-one-compound (OBOC) combinatorial library (Lam et al., Nature, 354:82-84, 1991). Examples of a peptide or peptidomimetic tethered to a dsRNA agent via an incorporated monomer unit for cell targeting purposes is an arginine-glycine-aspartic acid (RGD)-peptide, or RGD mimic. A peptide moiety can range in length from about 5 amino acids to about 40 amino acids. The peptide moieties can have a structural modification, such as to increase stability or direct conformational properties. Any of the structural modifications described below can be utilized. 
     An RGD peptide for use in the compositions and methods of the invention may be linear or cyclic, and may be modified, e.g., glycosylated or methylated, to facilitate targeting to a specific tissue(s). RGD-containing peptides and peptidiomimemtics may include D-amino acids, as well as synthetic RGD mimics. In addition to RGD, one can use other moieties that target the integrin ligand. Preferred conjugates of this ligand target PECAM-1 or VEGF. 
     A “cell permeation peptide” is capable of permeating a cell, e.g., a microbial cell, such as a bacterial or fungal cell, or a mammalian cell, such as a human cell. A microbial cell-permeating peptide can be, for example, an α-helical linear peptide (e.g., LL-37 or Ceropin P1), a disulfide bond-containing peptide (e.g., α-defensin, β-defensin or bactenecin), or a peptide containing only one or two dominating amino acids (e.g., PR-39 or indolicidin). A cell permeation peptide can also include a nuclear localization signal (NLS). For example, a cell permeation peptide can be a bipartite amphipathic peptide, such as MPG, which is derived from the fusion peptide domain of HIV-1 gp41 and the NLS of SV40 large T antigen (Simeoni et al., Nucl. Acids Res. 31:2717-2724, 2003). 
     C. Carbohydrate Conjugates 
     In some embodiments of the compositions and methods of the invention, an iRNA further comprises a carbohydrate. The carbohydrate conjugated iRNA is advantageous for the in vivo delivery of nucleic acids, as well as compositions suitable for in vivo therapeutic use, as described herein. As used herein, “carbohydrate” refers to a compound which is either a carbohydrate per se made up of one or more monosaccharide units having at least 6 carbon atoms (which can be linear, branched or cyclic) with an oxygen, nitrogen or sulfur atom bonded to each carbon atom; or a compound having as a part thereof a carbohydrate moiety made up of one or more monosaccharide units each having at least six carbon atoms (which can be linear, branched or cyclic), with an oxygen, nitrogen or sulfur atom bonded to each carbon atom. Representative carbohydrates include the sugars (mono-, di-, tri-, and oligosaccharides containing from about 4, 5, 6, 7, 8, or 9 monosaccharide units), and polysaccharides such as starches, glycogen, cellulose and polysaccharide gums. Specific monosaccharides include HBV and above (e.g., C5, C6, C7, or C8) sugars; di- and trisaccharides include sugars having two or three monosaccharide units (e.g., C5, C6, C7, or C8). 
     In one embodiment, a carbohydrate conjugate for use in the compositions and methods of the invention is a monosaccharide. In another embodiment, a carbohydrate conjugate for use in the compositions and methods of the invention is selected from the group consisting of: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In one embodiment, the monosaccharide is an N-acetylgalactosamine, such as 
     
       
         
         
             
             
         
       
     
     Another representative carbohydrate conjugate for use in the embodiments described herein includes, but is not limited to, 
     
       
         
         
             
             
         
       
     
     when one of X or Y is an oligonucleotide, the other is a hydrogen. 
     In certain embodiments of the invention, the GalNAc or GalNAc derivative is attached to an iRNA agent of the invention via a monovalent linker. In some embodiments, the GalNAc or GalNAc derivative is attached to an iRNA agent of the invention via a bivalent linker. In yet other embodiments of the invention, the GalNAc or GalNAc derivative is attached to an iRNA agent of the invention via a trivalent linker. 
     In one embodiment, the double stranded RNAi agents of the invention comprise one GalNAc or GalNAc derivative attached to the iRNA agent. In another embodiment, the double stranded RNAi agents of the invention comprise a plurality (e.g., 2, 3, 4, 5, or 6) GalNAc or GalNAc derivatives, each independently attached to a plurality of nucleotides of the double stranded RNAi agent through a plurality of monovalent linkers. 
     In some embodiments, for example, when the two strands of an iRNA agent of the invention are part of one larger molecule connected by an uninterrupted chain of nucleotides between the 3′-end of one strand and the 5′-end of the respective other strand forming a hairpin loop comprising, a plurality of unpaired nucleotides, each unpaired nucleotide within the hairpin loop may independently comprise a GalNAc or GalNAc derivative attached via a monovalent linker. The hairpin loop may also be formed by an extended overhang in one strand of the duplex. 
     In some embodiments, the carbohydrate conjugate further comprises one or more additional ligands as described above, such as, but not limited to, a PK modulator or a cell permeation peptide. 
     Additional carbohydrate conjugates suitable for use in the present invention include those described in PCT Publication Nos. WO 2014/179620 and WO 2014/179627, the entire contents of each of which are incorporated herein by reference. 
     D. Linkers 
     In some embodiments, the conjugate or ligand described herein can be attached to an iRNA oligonucleotide with various linkers that can be cleavable or non-cleavable. 
     The term “linker” or “linking group” means an organic moiety that connects two parts of a compound, e.g., covalently attaches two parts of a compound. Linkers typically comprise a direct bond or an atom such as oxygen or sulfur, a unit such as NR8, C(O), C(O)NH, SO, SO 2 , SO 2 NH or a chain of atoms, such as, but not limited to, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, arylalkyl, arylalkenyl, arylalkynyl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, heterocyclylalkyl, heterocyclylalkenyl, heterocyclylalkynyl, aryl, heteroaryl, heterocyclyl, cycloalkyl, cycloalkenyl, alkylarylalkyl, alkylarylalkenyl, alkylarylalkynyl, alkenylarylalkyl, alkenylarylalkenyl, alkenylarylalkynyl, alkynylarylalkyl, alkynylarylalkenyl, alkynylarylalkynyl, alkylheteroarylalkyl, alkylheteroarylalkenyl, alkylheteroarylalkynyl, alkenylheteroarylalkyl, alkenylheteroarylalkenyl, alkenylheteroarylalkynyl, alkynylheteroarylalkyl, alkynylheteroarylalkenyl, alkynylheteroarylalkynyl, alkylheterocyclylalkyl, alkylheterocyclylalkenyl, alkylhererocyclylalkynyl, alkenylheterocyclylalkyl, alkenylheterocyclylalkenyl, alkenylheterocyclylalkynyl, alkynylheterocyclylalkyl, alkynylheterocyclylalkenyl, alkynylheterocyclylalkynyl, alkylaryl, alkenylaryl, alkynylaryl, alkylheteroaryl, alkenylheteroaryl, alkynylhereroaryl, which one or more methylenes can be interrupted or terminated by O, S, S(O), SO 2 , N(R8), C(O), substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted heterocyclic; where R8 is hydrogen, acyl, aliphatic, or substituted aliphatic. In one embodiment, the linker is between about 1-24 atoms, 2-24, 3-24, 4-24, 5-24, 6-24, 6-18, 7-18, 8-18, 7-17, 8-17, 6-16, 7-16, or 8-16 atoms. 
     A cleavable linking group is one which is sufficiently stable outside the cell, but which upon entry into a target cell is cleaved to release the two parts the linker is holding together. In a preferred embodiment, the cleavable linking group is cleaved at least about 10 times, 20, times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, or 100 times faster in a target cell or under a first reference condition (which can, e.g., be selected to mimic or represent intracellular conditions) than in the blood of a subject, or under a second reference condition (which can, e.g., be selected to mimic or represent conditions found in the blood or serum). 
     Cleavable linking groups are susceptible to cleavage agents, e.g., pH, redox potential, or the presence of degradative molecules. Generally, cleavage agents are more prevalent or found at higher levels or activities inside cells than in serum or blood. Examples of such degradative agents include: redox agents which are selected for particular substrates or which have no substrate specificity, including, e.g., oxidative or reductive enzymes or reductive agents such as mercaptans, present in cells, that can degrade a redox cleavable linking group by reduction; esterases; endosomes or agents that can create an acidic environment, e.g., those that result in a pH of five or lower; enzymes that can hydrolyze or degrade an acid cleavable linking group by acting as a general acid, peptidases (which can be substrate specific), and phosphatases. 
     A cleavable linkage group, such as a disulfide bond can be susceptible to pH. The pH of human serum is 7.4, while the average intracellular pH is slightly lower, ranging from about 7.1-7.3. Endosomes have a more acidic pH, in the range of 5.5-6.0, and lysosomes have an even more acidic pH at around 5.0. Some linkers will have a cleavable linking group that is cleaved at a preferred pH, thereby releasing a cationic lipid from the ligand inside the cell, or into the desired compartment of the cell. 
     A linker can include a cleavable linking group that is cleavable by a particular enzyme. The type of cleavable linking group incorporated into a linker can depend on the cell to be targeted. For example, a liver-targeting ligand can be linked to a cationic lipid through a linker that includes an ester group. Liver cells are rich in esterases, and therefore the linker will be cleaved more efficiently in liver cells than in cell types that are not esterase-rich. Other cell-types rich in esterases include cells of the lung, renal cortex, and testis. 
     Linkers that contain peptide bonds can be used when targeting cell types rich in peptidases, such as liver cells and synoviocytes. 
     In general, the suitability of a candidate cleavable linking group can be evaluated by testing the ability of a degradative agent (or condition) to cleave the candidate linking group. It will also be desirable to also test the candidate cleavable linking group for the ability to resist cleavage in the blood or when in contact with other non-target tissue. Thus, one can determine the relative susceptibility to cleavage between a first and a second condition, where the first is selected to be indicative of cleavage in a target cell and the second is selected to be indicative of cleavage in other tissues or biological fluids, e.g., blood or serum. The evaluations can be carried out in cell free systems, in cells, in cell culture, in organ or tissue culture, or in whole animals. It can be useful to make initial evaluations in cell-free or culture conditions and to confirm by further evaluations in whole animals. In preferred embodiments, useful candidate compounds are cleaved at least about 2, 4, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 times faster in the cell (or under in vitro conditions selected to mimic intracellular conditions) as compared to blood or serum (or under in vitro conditions selected to mimic extracellular conditions). 
     i. Redox Cleavable Linking Groups 
     In certain embodiments, a cleavable linking group is a redox cleavable linking group that is cleaved upon reduction or oxidation. An example of reductively cleavable linking group is a disulphide linking group (—S—S—). To determine if a candidate cleavable linking group is a suitable “reductively cleavable linking group,” or for example is suitable for use with a particular iRNA moiety and particular targeting agent one can look to methods described herein. For example, a candidate can be evaluated by incubation with dithiothreitol (DTT), or other reducing agent using reagents know in the art, which mimic the rate of cleavage which would be observed in a cell, e.g., a target cell. The candidates can also be evaluated under conditions which are selected to mimic blood or serum conditions. In one, candidate compounds are cleaved by at most about 10% in the blood. In other embodiments, useful candidate compounds are degraded at least about 2, 4, 10, 20, 30, 40, 50, 60, 70, 80, 90, or about 100 times faster in the cell (or under in vitro conditions selected to mimic intracellular conditions) as compared to blood (or under in vitro conditions selected to mimic extracellular conditions). The rate of cleavage of candidate compounds can be determined using standard enzyme kinetics assays under conditions chosen to mimic intracellular media and compared to conditions chosen to mimic extracellular media. 
     ii. Phosphate-Based Cleavable Linking Groups 
     In other embodiments, a cleavable linker comprises a phosphate-based cleavable linking group. A phosphate-based cleavable linking group is cleaved by agents that degrade or hydrolyze the phosphate group. An example of an agent that cleaves phosphate groups in cells are enzymes such as phosphatases in cells. Examples of phosphate-based linking groups are —O-P(O)(ORk)-O—, —O—P(S)(ORk)-O—, —O—P(S)(SRk)-O—, —S-P(O)(ORk)-O—, —O—P(O)(ORk)-S—, —S-P(O)(ORk)-S—, —O—P(S)(ORk)-S—, —S—P(S)(ORk)-O—, —O-P(O)(Rk)-O—, —O—P(S)(Rk)-O—, —S-P(O)(Rk)-O—, —S—P(S)(Rk)-O—, —S-P(O)(Rk)-S—, —O—P(S)(Rk)-S—. Preferred embodiments are —O—P(O)(OH)—O—, —O—P(S)(OH)—O—, —O—P(S)(SH)—O—, —S—P(O)(OH)—O—, —O—P(O)(OH)—S—, —S—P(O)(OH)—S—, —O—P(S)(OH)—S—, —S—P(S)(OH)—O—, —O—P(O)(H)—O—, —O—P(S)(H)—O—, —S—P(O)(H)—O, —S—P(S)(H)—O—, —S—P(O)(H)—S—, and —O—P(S)(H)—S—. A preferred embodiment is —O—P(O)(OH)—O—. These candidates can be evaluated using methods analogous to those described above. 
     iii. Acid Cleavable Linking Groups 
     In other embodiments, a cleavable linker comprises an acid cleavable linking group. An acid cleavable linking group is a linking group that is cleaved under acidic conditions. In preferred embodiments acid cleavable linking groups are cleaved in an acidic environment with a pH of about 6.5 or lower (e.g., about 6.0, 5.5, 5.0, or lower), or by agents such as enzymes that can act as a general acid. In a cell, specific low pH organelles, such as endosomes and lysosomes can provide a cleaving environment for acid cleavable linking groups. Examples of acid cleavable linking groups include but are not limited to hydrazones, esters, and esters of amino acids. Acid cleavable groups can have the general formula —C═NN—, C(O)O, or —OC(O). A preferred embodiment is when the carbon attached to the oxygen of the ester (the alkoxy group) is an aryl group, substituted alkyl group, or tertiary alkyl group such as dimethyl pentyl or t-butyl. These candidates can be evaluated using methods analogous to those described above. 
     iv. Ester-Based Linking Groups 
     In other embodiments, a cleavable linker comprises an ester-based cleavable linking group. An ester-based cleavable linking group is cleaved by enzymes such as esterases and amidases in cells. Examples of ester-based cleavable linking groups include, but are not limited to, esters of alkylene, alkenylene and alkynylene groups. Ester cleavable linking groups have the general formula —C(O)O—, or —OC(O)—. These candidates can be evaluated using methods analogous to those described above. 
     v. Peptide-Based Cleaving Groups 
     In yet other embodiments, a cleavable linker comprises a peptide-based cleavable linking group. A peptide-based cleavable linking group is cleaved by enzymes such as peptidases and proteases in cells. Peptide-based cleavable linking groups are peptide bonds formed between amino acids to yield oligopeptides (e.g., dipeptides, tripeptides etc.) and polypeptides. Peptide-based cleavable groups do not include the amide group (—C(O)NH—). The amide group can be formed between any alkylene, alkenylene or alkynelene. A peptide bond is a special type of amide bond formed between amino acids to yield peptides and proteins. The peptide based cleavage group is generally limited to the peptide bond (i.e., the amide bond) formed between amino acids yielding peptides and proteins and does not include the entire amide functional group. Peptide-based cleavable linking groups have the general formula —NHCHRAC(O)NHCHRBC(O)—(SEQ ID NO: ______), where RA and RB are the R groups of the two adjacent amino acids. These candidates can be evaluated using methods analogous to those described above. 
     In some embodiments, an iRNA of the invention is conjugated to a carbohydrate through a linker. Non-limiting examples of iRNA carbohydrate conjugates with linkers of the compositions and methods of the invention include, but are not limited to, 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     when one of X or Y is an oligonucleotide, the other is a hydrogen. 
     In certain embodiments of the compositions and methods of the invention, a ligand is one or more “GalNAc” (N-acetylgalactosamine) derivatives attached through a bivalent or trivalent branched linker. 
     In certain embodiments, a dsRNA of the invention is conjugated to a bivalent or trivalent branched linker selected from the group of structures shown in any of formula (XXXII)-(XXXV): 
     
       
         
         
             
             
         
       
     
     wherein: 
     q2A, q2B, q3A, q3B, q4A, q4B, q5A, q5B and q5C represent independently for each occurrence 0-20 and wherein the repeating unit can be the same or different; 
     p 2A , p 2B , p 3A , p 3B , p 4A , p 4B , p 5A , p 5B , p 5C , T 2A , T 2B , T 3A , T 3B , T 4A , T 4B , T 4A , T 5B , T 5C  are each independently for each occurrence absent, CO, NH, O, S, OC(O), NHC(O), CH 2 , CH 2 NH, or CH 2 O; 
     Q 2A , Q 2B , Q 3A , Q 3B , Q 4A , Q 4B , Q 5A , Q 5B , Q 5C  are independently for each occurrence absent, alkylene, substituted alkylene wherein one or more methylenes can be interrupted or terminated by one or more of O, S, S(O), SO 2 , N(R N ), C(R′)═C(R″), C≡C, or C(O); 
     R 2A , R 2B , R 3A , R 3B , R 4A , R 4B , R 5A , R 5B , R 5C  are each independently for each occurrence absent, NH, O, S, CH 2 , C(O)O, C(O)NH, NHCH(R a )C(O), —C(O)—CH(R a )—NH—, CO, CH═N-O, 
     
       
         
         
             
             
         
       
     
     or heterocyclyl; 
     L 2A , L 2B , L 3A , L 3B , L 4A , L 4B , L 5A , L 5B , L 5C  represent the ligand; i.e. each independently for each occurrence a monosaccharide (such as GalNAc), disaccharide, trisaccharide, tetrasaccharide, oligosaccharide, or polysaccharide; and R a  is H or amino acid side chain. Trivalent conjugating GalNAc derivatives are particularly useful for use with RNAi agents for inhibiting the expression of a target gene, such as those of formula (XXXV): 
     
       
         
         
             
             
         
       
         
         
           
             wherein L 5A , L 5B  and L 5C  represent a monosaccharide, such as GalNAc derivative. 
           
         
       
    
     Examples of suitable bivalent and trivalent branched linker groups conjugating GalNAc derivatives include, but are not limited to, the structures recited above as formulas II, VII, XI, X, and XIII. 
     Representative US Patents that teach the preparation of RNA conjugates include, but are not limited to, U.S. Pat. Nos. 4,828,979; 4,948,882; 5,218,105; 5,525,465; 5,541,313; 5,545,730; 5,552,538; 5,578,717, 5,580,731; 5,591,584; 5,109,124; 5,118,802; 5,138,045; 5,414,077; 5,486,603; 5,512,439; 5,578,718; 5,608,046; 4,587,044; 4,605,735; 4,667,025; 4,762,779; 4,789,737; 4,824,941; 4,835,263; 4,876,335; 4,904,582; 4,958,013; 5,082,830; 5,112,963; 5,214,136; 5,082,830; 5,112,963; 5,214,136; 5,245,022; 5,254,469; 5,258,506; 5,262,536; 5,272,250; 5,292,873; 5,317,098; 5,371,241, 5,391,723; 5,416,203, 5,451,463; 5,510,475; 5,512,667; 5,514,785; 5,565,552; 5,567,810; 5,574,142; 5,585,481; 5,587,371; 5,595,726; 5,597,696; 5,599,923; 5,599,928; 5,688,941; 6,294,664; 6,320,017; 6,576,752; 6,783,931; 6,900,297; 7,037,646; and 8,106,022, the entire contents of each of which are hereby incorporated herein by reference. 
     It is not necessary for all positions in a given compound to be uniformly modified, and in fact more than one of the aforementioned modifications can be incorporated in a single compound or even at a single nucleoside within an iRNA. The present invention also includes iRNA compounds that are chimeric compounds. 
     “Chimeric” iRNA compounds or “chimeras,” in the context of this invention, are iRNA compounds, preferably dsRNAi agents, that contain two or more chemically distinct regions, each made up of at least one monomer unit, i.e., a nucleotide in the case of a dsRNA compound. These iRNAs typically contain at least one region wherein the RNA is modified so as to confer upon the iRNA increased resistance to nuclease degradation, increased cellular uptake, or increased binding affinity for the target nucleic acid. An additional region of the iRNA can serve as a substrate for enzymes capable of cleaving RNA:DNA or RNA:RNA hybrids. By way of example, RNase H is a cellular endonuclease which cleaves the RNA strand of an RNA:DNA duplex. Activation of RNase H, therefore, results in cleavage of the RNA target, thereby greatly enhancing the efficiency of iRNA inhibition of gene expression. Consequently, comparable results can often be obtained with shorter iRNAs when chimeric dsRNAs are used, compared to phosphorothioate deoxy dsRNAs hybridizing to the same target region. Cleavage of the RNA target can be routinely detected by gel electrophoresis and, if necessary, associated nucleic acid hybridization techniques known in the art. 
     In certain instances, the RNA of an iRNA can be modified by a non-ligand group. A number of non-ligand molecules have been conjugated to iRNAs in order to enhance the activity, cellular distribution or cellular uptake of the iRNA, and procedures for performing such conjugations are available in the scientific literature. Such non-ligand moieties have included lipid moieties, such as cholesterol (Kubo, T. et al.,  Biochem. Biophys. Res. Comm.,  2007, 365(1):54-61; Letsinger et al.,  Proc. Natl. Acad. Sci. USA,  1989, 86:6553) can be used in the agents of the invention. Other non-ligand moieties have included lipid moieties, cholic acid (Manoharan et al.,  Bioorg. Med. Chem. Lett.,  1994, 4:1053), a thioether, e.g., hexyl-S-tritylthiol (Manoharan et al.,  Ann. N.Y. Acad. Sci.,  1992, 660:306; Manoharan et al.,  Bioorg. Med. Chem. Let.,  1993, 3:2765), a thiocholesterol (Oberhauser et al.,  Nucl. Acids Res.,  1992, 20:533), an aliphatic chain, e.g., dodecandiol or undecyl residues (Saison-Behmoaras et al.,  EMBO J.,  1991, 10:111; Kabanov et al.,  FEBS Lett.,  1990, 259:327; Svinarchuk et al.,  Biochimie,  1993, 75:49), a phospholipid, e.g., di-hexadecyl-rac-glycerol or triethylammonium 1,2-di-O-hexadecyl-rac-glycero-3-H-phosphonate (Manoharan et al.,  Tetrahedron Lett.,  1995, 36:3651; Shea et al.,  Nucl. Acids Res.,  1990, 18:3777), a polyamine or a polyethylene glycol chain (Manoharan et al.,  Nucleosides  &amp;  Nucleotides,  1995, 14:969), or adamantane acetic acid (Manoharan et al.,  Tetrahedron Lett.,  1995, 36:3651), a palmityl moiety (Mishra et al.,  Biochim. Biophys. Acta,  1995, 1264:229), or an octadecylamine or hexylamino-carbonyl-oxycholesterol moiety (Crooke et al.,  J. Pharmacol. Exp. Ther.,  1996, 277:923). Representative United States patents that teach the preparation of such RNA conjugates have been listed above. Typical conjugation protocols involve the synthesis of RNAs bearing an aminolinker at one or more positions of the sequence. The amino group is then reacted with the molecule being conjugated using appropriate coupling or activating reagents. The conjugation reaction can be performed either with the RNA still bound to the solid support or following cleavage of the RNA, in solution phase. Purification of the RNA conjugate by HPLC typically affords the pure conjugate. 
     IV. Delivery of an iRNA of the Invention 
     The delivery of an iRNA of the invention to a cell e.g., a cell within a subject, such as a human subject (e.g., a subject in need thereof, such as a subject having a disease, disorder, or condition associated with PD-L1 gene expression) can be achieved in a number of different ways. For example, delivery may be performed by contacting a cell with an iRNA of the invention either in vitro or in vivo. In vivo delivery may also be performed directly by administering a composition comprising an iRNA, e.g., a dsRNA, to a subject. Alternatively, in vivo delivery may be performed indirectly by administering one or more vectors that encode and direct the expression of the iRNA. These alternatives are discussed further below. 
     In general, any method of delivering a nucleic acid molecule (in vitro or in vivo) can be adapted for use with an iRNA of the invention (see e.g., Akhtar S. and Julian R L. (1992)  Trends Cell. Biol.  2(5):139-144 and WO94/02595, which are incorporated herein by reference in their entireties). For in vivo delivery, factors to consider in order to deliver an iRNA molecule include, for example, biological stability of the delivered molecule, prevention of non-specific effects, and accumulation of the delivered molecule in the target tissue. The non-specific effects of an iRNA can be minimized by local administration, for example, by direct injection or implantation into a tissue or topically administering the preparation. Local administration to a treatment site maximizes local concentration of the agent, limits the exposure of the agent to systemic tissues that can otherwise be harmed by the agent or that can degrade the agent, and permits a lower total dose of the iRNA molecule to be administered. Several studies have shown successful knockdown of gene products when a dsRNAi agent is administered locally. For example, intraocular delivery of a VEGF dsRNA by intravitreal injection in cynomolgus monkeys (Tolentino, M J, et al (2004)  Retina  24:132-138) and subretinal injections in mice (Reich, S J., et al (2003)  Mol. Vis.  9:210-216) were both shown to prevent neovascularization in an experimental model of age-related macular degeneration. In addition, direct intratumoral injection of a dsRNA in mice reduces tumor volume (Pille, J., et al (2005)  Mol. Ther.  11:267-274) and can prolong survival of tumor-bearing mice (Kim, W J., et al (2006)  Mol. Ther.  14:343-350; Li, S., et al (2007)  Mol. Ther.  15:515-523). RNA interference has also shown success with local delivery to the CNS by direct injection (Dorn, G., et al. (2004)  Nucleic Acids  32:e49; Tan, P H., et al (2005)  Gene Ther.  12:59-66; Makimura, H., et al (2002)  BMC Neurosci.  3:18; Shishkina, G T., et al (2004)  Neuroscience  129:521-528; Thakker, E R., et al (2004)  Proc. Natl. Acad. Sci. USA.  101:17270-17275; Akaneya, Y., et al (2005)  J Neurophysiol.  93:594-602) and to the lungs by intranasal administration (Howard, K A., et al (2006)  Mol. Ther.  14:476-484; Zhang, X., et al (2004)  J. Biol. Chem.  279:10677-10684; Bitko, V., et al (2005)  Nat. Med.  11:50-55). For administering an iRNA systemically for the treatment of a disease, the RNA can be modified or alternatively delivered using a drug delivery system; both methods act to prevent the rapid degradation of the dsRNA by endo- and exo-nucleases in vivo. Modification of the RNA or the pharmaceutical carrier can also permit targeting of the iRNA to the target tissue and avoid undesirable off-target effects. iRNA molecules can be modified by chemical conjugation to lipophilic groups such as cholesterol to enhance cellular uptake and prevent degradation. For example, an iRNA directed against ApoB conjugated to a lipophilic cholesterol moiety was injected systemically into mice and resulted in knockdown of apoB mRNA in both the liver and jejunum (Soutschek, J., et al (2004)  Nature  432:173-178). Conjugation of an iRNA to an aptamer has been shown to inhibit tumor growth and mediate tumor regression in a mouse model of prostate cancer (McNamara, J O, et al (2006)  Nat. Biotechnol.  24:1005-1015). In an alternative embodiment, the iRNA can be delivered using drug delivery systems such as a nanoparticle, a dendrimer, a polymer, liposomes, or a cationic delivery system. Positively charged cationic delivery systems facilitate binding of an iRNA molecule (negatively charged) and also enhance interactions at the negatively charged cell membrane to permit efficient uptake of an iRNA by the cell. Cationic lipids, dendrimers, or polymers can either be bound to an iRNA, or induced to form a vesicle or micelle (see e.g., Kim S H, et al (2008)  Journal of Controlled Release  129(2):107-116) that encases an iRNA. The formation of vesicles or micelles further prevents degradation of the iRNA when administered systemically. Methods for making and administering cationic-iRNA complexes are well within the abilities of one skilled in the art (see e.g., Sorensen, D R, et al (2003)  J. Mol. Biol  327:761-766; Verma, U N, et al (2003)  Clin. Cancer Res.  9:1291-1300; Arnold, A S et al (2007)  J. Hypertens.  25:197-205, which are incorporated herein by reference in their entirety). Some non-limiting examples of drug delivery systems useful for systemic delivery of iRNAs include DOTAP (Sorensen, D R., et al (2003), supra; Verma, U N, et al (2003), supra), Oligofectamine, “solid nucleic acid lipid particles” (Zimmermann, T S, et al (2006)  Nature  441:111-114), cardiolipin (Chien, P Y, et al (2005)  Cancer Gene Ther.  12:321-328; Pal, A, et al (2005)  Int J. Oncol.  26:1087-1091), polyethyleneimine (Bonnet M E, et al (2008)  Pharm. Res . August 16 Epub ahead of print;  Aigner, A . (2006)  J. Biomed. Biotechnol.  71659), Arg-Gly-Asp (RGD) peptides (Liu, S. (2006)  Mol. Pharm.  3:472-487), and polyamidoamines (Tomalia, D A, et al (2007)  Biochem. Soc. Trans.  35:61-67; Yoo, H., et al (1999)  Pharm. Res.  16:1799-1804). In some embodiments, an iRNA forms a complex with cyclodextrin for systemic administration. Methods for administration and pharmaceutical compositions of iRNAs and cyclodextrins can be found in U.S. Pat. No. 7,427,605, which is herein incorporated by reference in its entirety. 
     A. Vector Encoded iRNAs of the Invention 
     iRNA targeting the PD-L1 gene can be expressed from transcription units inserted into DNA or RNA vectors (see, e.g., Couture, A, et al.,  TIG . (1996), 12:5-10; Skillern, A, et al., International PCT Publication No. WO 00/22113, Conrad, International PCT Publication No. WO 00/22114, and Conrad, U.S. Pat. No. 6,054,299). Expression can be transient (on the order of hours to weeks) or sustained (weeks to months or longer), depending upon the specific construct used and the target tissue or cell type. These transgenes can be introduced as a linear construct, a circular plasmid, or a viral vector, which can be an integrating or non-integrating vector. The transgene can also be constructed to permit it to be inherited as an extrachromosomal plasmid (Gassmann, et al.,  Proc. Natl. Acad. Sci. USA  (1995) 92:1292). 
     The individual strand or strands of an iRNA can be transcribed from a promoter on an expression vector. Where two separate strands are to be expressed to generate, for example, a dsRNA, two separate expression vectors can be co-introduced (e.g., by transfection or infection) into a target cell. Alternatively each individual strand of a dsRNA can be transcribed by promoters both of which are located on the same expression plasmid. In one embodiment, a dsRNA is expressed as inverted repeat polynucleotides joined by a linker polynucleotide sequence such that the dsRNA has a stem and loop structure. 
     iRNA expression vectors are generally DNA plasmids or viral vectors. Expression vectors compatible with eukaryotic cells, preferably those compatible with vertebrate cells, can be used to produce recombinant constructs for the expression of an iRNA as described herein. Eukaryotic cell expression vectors are well known in the art and are available from a number of commercial sources. Typically, such vectors are provided containing convenient restriction sites for insertion of the desired nucleic acid segment. Delivery of iRNA expressing vectors can be systemic, such as by intravenous or intramuscular administration, by administration to target cells ex-planted from the patient followed by reintroduction into the patient, or by any other means that allows for introduction into a desired target cell. 
     Viral vector systems which can be utilized with the methods and compositions described herein include, but are not limited to, (a) adenovirus vectors; (b) retrovirus vectors, including but not limited to lentiviral vectors, moloney murine leukemia virus, etc.; (c) adeno-associated virus vectors; (d) herpes simplex virus vectors; (e) SV 40 vectors; (f) polyoma virus vectors; (g) papilloma virus vectors; (h) picornavirus vectors; (i) pox virus vectors such as an orthopox, e.g., vaccinia virus vectors or avipox, e.g. canary pox or fowl pox; and (j) a helper-dependent or gutless adenovirus. Replication-defective viruses can also be advantageous. Different vectors will or will not become incorporated into the cells&#39; genome. The constructs can include viral sequences for transfection, if desired. Alternatively, the construct can be incorporated into vectors capable of episomal replication, e.g. EPV and EBV vectors. Constructs for the recombinant expression of an iRNA will generally require regulatory elements, e.g., promoters, enhancers, etc., to ensure the expression of the iRNA in target cells. Other aspects to consider for vectors and constructs are known in the art. 
     V. Pharmaceutical Compositions of the Invention 
     The present invention also includes pharmaceutical compositions and formulations which include the iRNAs of the invention. In one embodiment, provided herein are pharmaceutical compositions containing an iRNA, as described herein, and a pharmaceutically acceptable carrier. The pharmaceutical compositions containing the iRNA are useful for treating a disease or disorder associated with the expression or activity of a PD-L1 gene. Such pharmaceutical compositions are formulated based on the mode of delivery. One example is compositions that are formulated for systemic administration via parenteral delivery, e.g., by subcutaneous (SC) or intravenous (IV) delivery. The pharmaceutical compositions of the invention may be administered in dosages sufficient to inhibit expression of a PD-L1 gene. 
     The pharmaceutical compositions of the invention may be administered in dosages sufficient to inhibit expression of a PD-L1 gene. In general, a suitable dose of an iRNA of the invention will be in the range of about 0.001 to about 200.0 milligrams per kilogram body weight of the recipient per day, generally in the range of about 1 to 50 mg per kilogram body weight per day. Typically, a suitable dose of an iRNA of the invention will be in the range of about 0.1 mg/kg to about 5.0 mg/kg, e.g., about 0.3 mg/kg and about 3.0 mg/kg. A repeat-dose regimine may include administration of a therapeutic amount of iRNA on a regular basis, such as every other day or once a year. In certain embodiments, the iRNA is administered about once per month to about once per quarter (i.e., about once every three months). 
     After an initial treatment regimen, the treatments can be administered on a less frequent basis. For example, after administration weekly or biweekly for three months, administration can be repeated once per month, for six months, or a year; or longer. 
     The pharmaceutical composition can be administered once daily, or the iRNA can be administered as two, three, or more sub-doses at appropriate intervals throughout the day or even using continuous infusion or delivery through a controlled release formulation. In that case, the iRNA contained in each sub-dose must be correspondingly smaller in order to achieve the total daily dosage. The dosage unit can also be compounded for delivery over several days, e.g., using a conventional sustained release formulation which provides sustained release of the iRNA over a several day period. Sustained release formulations are well known in the art and are particularly useful for delivery of agents at a particular site, such as could be used with the agents of the present invention. In this embodiment, the dosage unit contains a corresponding multiple of the daily dose. 
     In other embodiments, a single dose of the pharmaceutical compositions can be long lasting, such that subsequent doses are administered at not more than 3, 4, or 5 day intervals, or at not more than 1, 2, 3, or 4 week intervals. In some embodiments of the invention, a single dose of the pharmaceutical compositions of the invention is administered once per week. In other embodiments of the invention, a single dose of the pharmaceutical compositions of the invention is administered bi-monthly. In certain embodiments, the iRNA is administered about once per month to about once per quarter (i.e., about once every three months). 
     The skilled artisan will appreciate that certain factors can influence the dosage and timing required to effectively treat a subject, including but not limited to the severity of the disease or disorder, previous treatments, the general health or age of the subject, and other diseases present. Moreover, treatment of a subject with a therapeutically effective amount of a composition can include a single treatment or a series of treatments. Estimates of effective dosages and in vivo half-lives for the individual iRNAs encompassed by the invention can be made using conventional methodologies or on the basis of in vivo testing using an appropriate animal model, as known in the art. 
     For example, animal models of hepatitis B infection are known in the art including chimpanzee, woodchuck, and transgenic mouse models of HBV (Wieland, 2015. Cold Spring Harb. Perspect. Med., 5:a021469, 2015; Tennant and Gerin, 2001. ILAR Journal, 42:89-102; and Moriyama et al., 1990. Science, 248:361-364). The chimpanzee model can also be used as a model for hepatitis D infection. A large number of cancer models including chemically induced and xenograft tumors are known in the art. 
     The pharmaceutical compositions of the present invention can be administered in a number of ways depending upon whether local or systemic treatment is desired and upon the area to be treated. Administration can be topical (e.g., by a transdermal patch), pulmonary, e.g., by inhalation or insufflation of powders or aerosols, including by nebulizer; intratracheal, intranasal, epidermal and transdermal, oral or parenteral. Parenteral administration includes intravenous, intraarterial, subcutaneous, intraperitoneal, or intramuscular injection or infusion; subdermal, e.g., via an implanted device; or intracranial, e.g., by intraparenchymal, intrathecal or intraventricular administration. 
     The iRNA can be delivered in a manner to target a particular tissue (e.g., liver cells). 
     Pharmaceutical compositions and formulations for topical or transdermal administration can include transdermal patches, ointments, lotions, creams, gels, drops, suppositories, sprays, liquids and powders. Conventional pharmaceutical carriers, aqueous, powder or oily bases, thickeners and the like can be necessary or desirable. Coated condoms, gloves and the like can also be useful. Suitable topical formulations include those in which the iRNAs featured in the invention are in admixture with a topical delivery agent such as lipids, liposomes, fatty acids, fatty acid esters, steroids, chelating agents and surfactants. Suitable lipids and liposomes include neutral (e.g., dioleoylphosphatidyl DOPE ethanolamine, dimyristoylphosphatidyl choline DMPC, distearolyphosphatidyl choline) negative (e.g., dimyristoylphosphatidyl glycerol DMPG) and cationic (e.g., dioleoyltetramethylaminopropyl DOTAP and dioleoylphosphatidyl ethanolamine DOTMA). iRNAs featured in the invention can be encapsulated within liposomes or can form complexes thereto, in particular to cationic liposomes. Alternatively, iRNAs can be complexed to lipids, in particular to cationic lipids. Suitable fatty acids and esters include but are not limited to arachidonic acid, oleic acid, eicosanoic acid, lauric acid, caprylic acid, capric acid, myristic acid, palmitic acid, stearic acid, linoleic acid, linolenic acid, dicaprate, tricaprate, monoolein, dilaurin, glyceryl 1-monocaprate, 1-dodecylazacycloheptan-2-one, an acylcarnitine, an acylcholine, or a C 1-20  alkyl ester (e.g., isopropylmyristate IPM), monoglyceride, diglyceride or pharmaceutically acceptable salt thereof). Topical formulations are described in detail in U.S. Pat. No. 6,747,014, which is incorporated herein by reference. 
     A. iRNA Formulations Comprising Membranous Molecular Assemblies 
     An iRNA for use in the compositions and methods of the invention can be formulated for delivery in a membranous molecular assembly, e.g., a liposome or a micelle. As used herein, the term “liposome” refers to a vesicle composed of amphiphilic lipids arranged in at least one bilayer, e.g., one bilayer or a plurality of bilayers. Liposomes include unilamellar and multilamellar vesicles that have a membrane formed from a lipophilic material and an aqueous interior. The aqueous portion contains the iRNA. The lipophilic material isolates the aqueous interior from an aqueous exterior, which typically does not include the iRNA composition, although in some examples, it may. Liposomes are useful for the transfer and delivery of active ingredients to the site of action. Because the liposomal membrane is structurally similar to biological membranes, when liposomes are applied to a tissue, the liposomal bilayer fuses with bilayer of the cellular membranes. As the merging of the liposome and cell progresses, the internal aqueous contents that include the iRNA are delivered into the cell where the iRNA can specifically bind to a target RNA and can mediate RNA interference. In some cases the liposomes are also specifically targeted, e.g., to direct the iRNA to particular cell types. 
     A liposome containing an iRNA agent can be prepared by a variety of methods. In one example, the lipid component of a liposome is dissolved in a detergent so that micelles are formed with the lipid component. For example, the lipid component can be an amphipathic cationic lipid or lipid conjugate. The detergent can have a high critical micelle concentration and may be nonionic. Exemplary detergents include cholate, CHAPS, octylglucoside, deoxycholate, and lauroyl sarcosine. The iRNA agent preparation is then added to the micelles that include the lipid component. The cationic groups on the lipid interact with the iRNA agent and condense around the iRNA agent to form a liposome. After condensation, the detergent is removed, e.g., by dialysis, to yield a liposomal preparation of iRNA agent. 
     If necessary a carrier compound that assists in condensation can be added during the condensation reaction, e.g., by controlled addition. For example, the carrier compound can be a polymer other than a nucleic acid (e.g., spermine or spermidine). pH can also adjusted to favor condensation. 
     Methods for producing stable polynucleotide delivery vehicles, which incorporate a polynucleotide/cationic lipid complex as structural components of the delivery vehicle, are further described in, e.g., WO 96/37194, the entire contents of which are incorporated herein by reference. Liposome formation can also include one or more aspects of exemplary methods described in Felgner, P. L. et al.,  Proc. Natl. Acad. Sci., USA  8:7413-7417, 1987; U.S. Pat. Nos. 4,897,355; 5,171,678; Bangham, et al.  M. Mol. Biol.  23:238, 1965; Olson, et al.  Biochim. Biophys. Acta  557:9, 1979; Szoka, et al.  Proc. Natl. Acad. Sci.  75: 4194, 1978; Mayhew, et al.  Biochim. Biophys. Acta  775:169, 1984; Kim, et al.  Biochim. Biophys. Acta  728:339, 1983; and Fukunaga, et al.  Endocrinol.  115:757, 1984. Commonly used techniques for preparing lipid aggregates of appropriate size for use as delivery vehicles include sonication and freeze-thaw plus extrusion (see, e.g., Mayer, et al.  Biochim. Biophys. Acta  858:161, 1986). Microfluidization can be used when consistently small (50 to 200 nm) and relatively uniform aggregates are desired (Mayhew, et al.  Biochim. Biophys. Acta  775:169, 1984). These methods are readily adapted to packaging iRNA agent preparations into liposomes. 
     Liposomes fall into two broad classes. Cationic liposomes are positively charged liposomes which interact with the negatively charged nucleic acid molecules to form a stable complex. The positively charged nucleic acid/liposome complex binds to the negatively charged cell surface and is internalized in an endosome. Due to the acidic pH within the endosome, the liposomes are ruptured, releasing their contents into the cell cytoplasm (Wang et al.,  Biochem. Biophys. Res. Commun.,  1987, 147, 980-985). 
     Liposomes which are pH-sensitive or negatively-charged, entrap nucleic acids rather than complex with it. Since both the nucleic acid and the lipid are similarly charged, repulsion rather than complex formation occurs. Nevertheless, some nucleic acid is entrapped within the aqueous interior of these liposomes. pH-sensitive liposomes have been used to deliver nucleic acids encoding the thymidine kinase gene to cell monolayers in culture. Expression of the exogenous gene was detected in the target cells (Zhou et al.,  Journal of Controlled Release,  1992, 19, 269-274). 
     One major type of liposomal composition includes phospholipids other than naturally-derived phosphatidylcholine. Neutral liposome compositions, for example, can be formed from dimyristoyl phosphatidylcholine (DMPC) or dipalmitoyl phosphatidylcholine (DPPC). Anionic liposome compositions generally are formed from dimyristoyl phosphatidylglycerol, while anionic fusogenic liposomes are formed primarily from dioleoyl phosphatidylethanolamine (DOPE). Another type of liposomal composition is formed from phosphatidylcholine (PC) such as, for example, soybean PC, and egg PC. Another type is formed from mixtures of two or more of phospholipid, phosphatidylcholine, and cholesterol. 
     Examples of other methods to introduce liposomes into cells in vitro and in vivo include U.S. Pat. Nos. 5,283,185 and 5,171,678; WO 94/00569; WO 93/24640; WO 91/16024; Felgner,  J. Biol. Chem.  269:2550, 1994; Nabel,  Proc. Natl. Acad. Sci.  90:11307, 1993; Nabel,  Human Gene Ther.  3:649, 1992; Gershon,  Biochem.  32:7143, 1993; and Strauss  EMBO J.  11:417, 1992. 
     Non-ionic liposomal systems have also been examined to determine their utility in the delivery of drugs to the skin, in particular systems comprising non-ionic surfactant and cholesterol. Non-ionic liposomal formulations comprising Novasome™ I (glyceryl dilaurate/cholesterol/polyoxyethylene-10-stearyl ether) and Novasome™ II (glyceryl distearate/cholesterol/polyoxyethylene-10-stearyl ether) were used to deliver cyclosporin-A into the dermis of mouse skin. Results indicated that such non-ionic liposomal systems were effective in facilitating the deposition of cyclosporine A into different layers of the skin (Hu et al.  S.T.P. Pharma. Sci.,  1994, 4(6) 466). 
     Liposomes also include “sterically stabilized” liposomes, a term which, as used herein, refers to liposomes comprising one or more specialized lipids that, when incorporated into liposomes, result in enhanced circulation lifetimes relative to liposomes lacking such specialized lipids. Examples of sterically stabilized liposomes are those in which part of the vesicle-forming lipid portion of the liposome (A) comprises one or more glycolipids, such as monosialoganglioside G M1 , or (B) is derivatized with one or more hydrophilic polymers, such as a polyethylene glycol (PEG) moiety. While not wishing to be bound by any particular theory, it is thought in the art that, at least for sterically stabilized liposomes containing gangliosides, sphingomyelin, or PEG-derivatized lipids, the enhanced circulation half-life of these sterically stabilized liposomes derives from a reduced uptake into cells of the reticuloendothelial system (RES) (Allen et al.,  FEBS Letters,  1987, 223, 42; Wu et al.,  Cancer Research,  1993, 53, 3765). 
     Various liposomes comprising one or more glycolipids are known in the art. Papahadjopoulos et al. ( Ann. N.Y. Acad. Sci.,  1987, 507, 64) reported the ability of monosialoganglioside G M1 , galactocerebroside sulfate and phosphatidylinositol to improve blood half-lives of liposomes. These findings were expounded upon by Gabizon et al. ( Proc. Natl. Acad. Sci. USA.,  1988, 85, 6949). U.S. Pat. No. 4,837,028 and WO 88/04924, both to Allen et al., disclose liposomes comprising (1) sphingomyelin and (2) the ganglioside G M1  or a galactocerebroside sulfate ester. U.S. Pat. No. 5,543,152 (Webb et al.) discloses liposomes comprising sphingomyelin. Liposomes comprising 1,2-sn-dimyristoylphosphatidylcholine are disclosed in WO 97/13499 (Lim et al). 
     In some embodiments, cationic liposomes are used. Cationic liposomes possess the advantage of being able to fuse to the cell membrane. Non-cationic liposomes, although not able to fuse as efficiently with the plasma membrane, are taken up by macrophages in vivo and can be used to deliver iRNA agents to macrophages. 
     Further advantages of liposomes include: liposomes obtained from natural phospholipids are biocompatible and biodegradable; liposomes can incorporate a wide range of water and lipid soluble drugs; liposomes can protect encapsulated iRNAs in their internal compartments from metabolism and degradation (Rosoff, in “Pharmaceutical Dosage Forms,” Lieberman, Rieger and Banker (Eds.), 1988, volume 1, p. 245). Important considerations in the preparation of liposome formulations are the lipid surface charge, vesicle size, and the aqueous volume of the liposomes. 
     A positively charged synthetic cationic lipid, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) can be used to form small liposomes that interact spontaneously with nucleic acid to form lipid-nucleic acid complexes which are capable of fusing with the negatively charged lipids of the cell membranes of tissue culture cells, resulting in delivery of iRNA agent (see, e.g., Felgner, P. L. et al., Proc. Natl. Acad. Sci., USA 8:7413-7417, 1987 and U.S. Pat. No. 4,897,355 for a description of DOTMA and its use with DNA). 
     A DOTMA analogue, 1,2-bis(oleoyloxy)-3-(trimethylammonia)propane (DOTAP) can be used in combination with a phospholipid to form DNA-complexing vesicles. Lipofectin™ (Bethesda Research Laboratories, Gaithersburg, Md.) is an effective agent for the delivery of highly anionic nucleic acids into living tissue culture cells that comprise positively charged DOTMA liposomes which interact spontaneously with negatively charged polynucleotides to form complexes. When enough positively charged liposomes are used, the net charge on the resulting complexes is also positive. Positively charged complexes prepared in this way spontaneously attach to negatively charged cell surfaces, fuse with the plasma membrane, and efficiently deliver functional nucleic acids into, for example, tissue culture cells. Another commercially available cationic lipid, 1,2-bis(oleoyloxy)-3,3-(trimethylammonia)propane (“DOTAP”) (Boehringer Mannheim, Indianapolis, Ind.) differs from DOTMA in that the oleoyl moieties are linked by ester, rather than ether linkages. 
     Other reported cationic lipid compounds include those that have been conjugated to a variety of moieties including, for example, carboxyspermine which has been conjugated to one of two types of lipids and includes compounds such as 5-carboxyspermylglycine dioctaoleoylamide (“DOGS”) (Transfectam™, Promega, Madison, Wis.) and dipalmitoylphosphatidylethanolamine 5-carboxyspermyl-amide (“DPPES”) (see, e.g., U.S. Pat. No. 5,171,678). 
     Another cationic lipid conjugate includes derivatization of the lipid with cholesterol (“DC-Chol”) which has been formulated into liposomes in combination with DOPE (See, Gao, X. and Huang, L.,  Biochim. Biophys. Res. Commun.  179:280, 1991). Lipopolylysine, made by conjugating polylysine to DOPE, has been reported to be effective for transfection in the presence of serum (Zhou, X. et al.,  Biochim. Biophys. Acta  1065:8, 1991). For certain cell lines, these liposomes containing conjugated cationic lipids, are said to exhibit lower toxicity and provide more efficient transfection than the DOTMA-containing compositions. Other commercially available cationic lipid products include DMRIE and DMRIE-HP (Vical, La Jolla, Calif.) and Lipofectamine (DOSPA) (Life Technology, Inc., Gaithersburg, Md.). Other cationic lipids suitable for the delivery of oligonucleotides are described in WO 98/39359 and WO 96/37194. 
     Liposomal formulations are particularly suited for topical administration, liposomes present several advantages over other formulations. Such advantages include reduced side effects related to high systemic absorption of the administered drug, increased accumulation of the administered drug at the desired target, and the ability to administer iRNA agent into the skin. In some implementations, liposomes are used for delivering iRNA agent to epidermal cells and also to enhance the penetration of iRNA agent into dermal tissues, e.g., into skin. For example, the liposomes can be applied topically. Topical delivery of drugs formulated as liposomes to the skin has been documented (see, e.g., Weiner et al.,  Journal of Drug Targeting,  1992, vol. 2, 405-410 and du Plessis et al.,  Antiviral Research,  18, 1992, 259-265; Mannino, R. J. and Fould-Fogerite, S.,  Biotechniques  6:682-690, 1988; Itani, T. et al.  Gene  56:267-276. 1987; Nicolau, C. et al.  Meth. Enz.  149:157-176, 1987; Straubinger, R. M. and Papahadjopoulos, D.  Meth. Enz.  101:512-527, 1983; Wang, C. Y. and Huang, L.,  Proc. Natl. Acad. Sci. USA  84:7851-7855, 1987). 
     Non-ionic liposomal systems have also been examined to determine their utility in the delivery of drugs to the skin, in particular systems comprising non-ionic surfactant and cholesterol. Non-ionic liposomal formulations comprising Novasome™ I (glyceryl dilaurate/cholesterol/polyoxyethylene-10-stearyl ether) and Novasome™ II (glyceryl distearate/cholesterol/polyoxyethylene-10-stearyl ether) were used to deliver a drug into the dermis of mouse skin. Such formulations with iRNA agent are useful for treating a dermatological disorder. 
     Liposomes that include iRNA can be made highly deformable. Such deformability can enable the liposomes to penetrate through pore that are smaller than the average radius of the liposome. For example, transfersomes are a type of deformable liposomes. Transferosomes can be made by adding surface edge activators, usually surfactants, to a standard liposomal composition. Transfersomes that include iRNAs can be delivered, for example, subcutaneously by infection in order to deliver iRNAs to keratinocytes in the skin. In order to cross intact mammalian skin, lipid vesicles must pass through a series of fine pores, each with a diameter less than 50 nm, under the influence of a suitable transdermal gradient. In addition, due to the lipid properties, these transfersomes can be self-optimizing (adaptive to the shape of pores, e.g., in the skin), self-repairing, and can frequently reach their targets without fragmenting, and often self-loading. 
     Other formulations amenable to the present invention are described in WO/2008/042973. 
     Transfersomes are yet another type of liposomes, and are highly deformable lipid aggregates which are attractive candidates for drug delivery vehicles. Transfersomes can be described as lipid droplets which are so highly deformable that they are easily able to penetrate through pores which are smaller than the droplet. Transfersomes are adaptable to the environment in which they are used, e.g., they are self-optimizing (adaptive to the shape of pores in the skin), self-repairing, frequently reach their targets without fragmenting, and often self-loading. To make transfersomes it is possible to add surface edge-activators, usually surfactants, to a standard liposomal composition. Transfersomes have been used to deliver serum albumin to the skin. The transfersome-mediated delivery of serum albumin has been shown to be as effective as subcutaneous injection of a solution containing serum albumin. 
     Surfactants find wide application in formulations such as emulsions (including microemulsions) and liposomes. The most common way of classifying and ranking the properties of the many different types of surfactants, both natural and synthetic, is by the use of the hydrophile/lipophile balance (HLB). The nature of the hydrophilic group (also known as the “head”) provides the most useful means for categorizing the different surfactants used in formulations (Rieger, in “Pharmaceutical Dosage Forms”, Marcel Dekker, Inc., New York, N.Y., 1988, p. 285). 
     If the surfactant molecule is not ionized, it is classified as a nonionic surfactant. Nonionic surfactants find wide application in pharmaceutical and cosmetic products and are usable over a wide range of pH values. In general their HLB values range from 2 to about 18 depending on their structure. Nonionic surfactants include nonionic esters such as ethylene glycol esters, propylene glycol esters, glyceryl esters, polyglyceryl esters, sorbitan esters, sucrose esters, and ethoxylated esters. Nonionic alkanolamides and ethers such as fatty alcohol ethoxylates, propoxylated alcohols, and ethoxylated/propoxylated block polymers are also included in this class. The polyoxyethylene surfactants are the most popular members of the nonionic surfactant class. 
     If the surfactant molecule carries a negative charge when it is dissolved or dispersed in water, the surfactant is classified as anionic. Anionic surfactants include carboxylates such as soaps, acyl lactylates, acyl amides of amino acids, esters of sulfuric acid such as alkyl sulfates and ethoxylated alkyl sulfates, sulfonates such as alkyl benzene sulfonates, acyl isethionates, acyl taurates and sulfosuccinates, and phosphates. The most important members of the anionic surfactant class are the alkyl sulfates and the soaps. 
     If the surfactant molecule carries a positive charge when it is dissolved or dispersed in water, the surfactant is classified as cationic. Cationic surfactants include quaternary ammonium salts and ethoxylated amines. The quaternary ammonium salts are the most used members of this class. 
     If the surfactant molecule has the ability to carry either a positive or negative charge, the surfactant is classified as amphoteric. Amphoteric surfactants include acrylic acid derivatives, substituted alkylamides, N-alkylbetaines and phosphatides. 
     The use of surfactants in drug products, formulations and in emulsions has been reviewed (Rieger, in “Pharmaceutical Dosage Forms”, Marcel Dekker, Inc., New York, N.Y., 1988, p. 285). 
     The iRNA for use in the methods of the invention can also be provided as micellar formulations. “Micelles” are defined herein as a particular type of molecular assembly in which amphipathic molecules are arranged in a spherical structure such that all the hydrophobic portions of the molecules are directed inward, leaving the hydrophilic portions in contact with the surrounding aqueous phase. The converse arrangement exists if the environment is hydrophobic. 
     A mixed micellar formulation suitable for delivery through transdermal membranes may be prepared by mixing an aqueous solution of iRNA, an alkali metal C 8  to C 22  alkyl sulphate, and a micelle forming compounds. Exemplary micelle forming compounds include lecithin, hyaluronic acid, pharmaceutically acceptable salts of hyaluronic acid, glycolic acid, lactic acid, chamomile extract, cucumber extract, oleic acid, linoleic acid, linolenic acid, monoolein, monooleates, monolaurates, borage oil, evening of primrose oil, menthol, trihydroxy oxo cholanyl glycine and pharmaceutically acceptable salts thereof, glycerin, polyglycerin, lysine, polylysine, triolein, polyoxyethylene ethers and analogues thereof, polidocanol alkyl ethers and analogues thereof, chenodeoxycholate, deoxycholate, and mixtures thereof. The micelle forming compounds may be added at the same time or after addition of the alkali metal alkyl sulphate. Mixed micelles will form with substantially any kind of mixing of the ingredients but vigorous mixing in order to provide smaller size micelles. 
     In one method a first micellar composition is prepared which contains the RNAi and at least the alkali metal alkyl sulphate. The first micellar composition is then mixed with at least three micelle forming compounds to form a mixed micellar composition. In another method, the micellar composition is prepared by mixing the RNAi, the alkali metal alkyl sulphate and at least one of the micelle forming compounds, followed by addition of the remaining micelle forming compounds, with vigorous mixing. 
     Phenol or m-cresol may be added to the mixed micellar composition to stabilize the formulation and protect against bacterial growth. Alternatively, phenol or m-cresol may be added with the micelle forming ingredients. An isotonic agent such as glycerin may also be added after formation of the mixed micellar composition. 
     For delivery of the micellar formulation as a spray, the formulation can be put into an aerosol dispenser and the dispenser is charged with a propellant. The propellant, which is under pressure, is in liquid form in the dispenser. The ratios of the ingredients are adjusted so that the aqueous and propellant phases become one, i.e., there is one phase. If there are two phases, it is necessary to shake the dispenser prior to dispensing a portion of the contents, e.g., through a metered valve. The dispensed dose of pharmaceutical agent is propelled from the metered valve in a fine spray. 
     Propellants may include hydrogen-containing chlorofluorocarbons, hydrogen-containing fluorocarbons, dimethyl ether and diethyl ether. In certain embodiments, HFA 134a (1,1,1,2 tetrafluoroethane) may be used. 
     The specific concentrations of the essential ingredients can be determined by relatively straightforward experimentation. For absorption through the oral cavities, it is often desirable to increase, e.g., at least double or triple, the dosage for through injection or administration through the gastrointestinal tract. 
     B. Lipid Particles 
     iRNAs, e.g., dsRNAi agents of in the invention may be fully encapsulated in a lipid formulation, e.g., a LNP, or other nucleic acid-lipid particle. 
     As used herein, the term “LNP” refers to a stable nucleic acid-lipid particle. LNPs typically contain a cationic lipid, a non-cationic lipid, and a lipid that prevents aggregation of the particle (e.g., a PEG-lipid conjugate). LNPs are extremely useful for systemic applications, as they exhibit extended circulation lifetimes following intravenous (i.v.) injection and accumulate at distal sites (e.g., sites physically separated from the administration site). LNPs include “pSPLP,” which include an encapsulated condensing agent-nucleic acid complex as set forth in PCT Publication No. WO 00/03683. The particles of the present invention typically have a mean diameter of about 50 nm to about 150 nm, more typically about 60 nm to about 130 nm, more typically about 70 nm to about 110 nm, most typically about 70 nm to about 90 nm, and are substantially nontoxic. In addition, the nucleic acids when present in the nucleic acid-lipid particles of the present invention are resistant in aqueous solution to degradation with a nuclease. Nucleic acid-lipid particles and their method of preparation are disclosed in, e.g., U.S. Pat. Nos. 5,976,567; 5,981,501; 6,534,484; 6,586,410; 6,815,432; US Publication No. 2010/0324120 and PCT Publication No. WO 96/40964. 
     In one embodiment, the lipid to drug ratio (mass/mass ratio) (e.g., lipid to dsRNA ratio) will be in the range of from about 1:1 to about 50:1, from about 1:1 to about 25:1, from about 3:1 to about 15:1, from about 4:1 to about 10:1, from about 5:1 to about 9:1, or about 6:1 to about 9:1. Ranges intermediate to the above recited ranges are also contemplated to be part of the invention. 
     The cationic lipid can be, for example, N,N-dioleyl-N,N-dimethylammonium chloride (DODAC), N,N-distearyl-N,N-dimethylammonium bromide (DDAB), N-(I-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP), N-(I-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), N,N-dimethyl-2,3-dioleyloxy)propylamine (DODMA), 1,2-DiLinoleyloxy-N,N-dimethylaminopropane (DLinDMA), 1,2-Dilinolenyloxy-N,N-dimethylaminopropane (DLenDMA), 1,2-Dilinoleylcarbamoyloxy-3-dimethylaminopropane (DLin-C-DAP), 1,2-Dilinoleyoxy-3-(dimethylamino)acetoxypropane (DLin-DAC), 1,2-Dilinoleyoxy-3-morpholinopropane (DLin-MA), 1,2-Dilinoleoyl-3-dimethylaminopropane (DLinDAP), 1,2-Dilinoleylthio-3-dimethylaminopropane (DLin-S-DMA), 1-Linoleoyl-2-linoleyloxy-3-dimethylaminopropane (DLin-2-DMAP), 1,2-Dilinoleyloxy-3-trimethylaminopropane chloride salt (DLin-TMA.Cl), 1,2-Dilinoleoyl-3-trimethylaminopropane chloride salt (DLin-TAP.Cl), 1,2-Dilinoleyloxy-3-(N-methylpiperazino)propane (DLin-MPZ), or 3-(N,N-Dilinoleylamino)-1,2-propanediol (DLinAP), 3-(N,N-Dioleylamino)-1,2-propanedio (DOAP), 1,2-Dilinoleyloxo-3-(2-N,N-dimethylamino)ethoxypropane (DLin-EG-DMA), 1,2-Dilinolenyloxy-N,N-dimethylaminopropane (DLinDMA), 2,2-Dilinoleyl-4-dimethylaminomethyl-[1,3]-dioxolane (DLin-K-DMA) or analogs thereof, (3aR,5s,6aS)—N,N-dimethyl-2,2-di((9Z,12Z)-octadeca-9,12-dienyl)tetrahydro-3aH-cyclopenta[d][1,3]dioxol-5-amine (ALN100), (6Z,9Z,28Z,31Z)-heptatriaconta-6,9,28,31-tetraen-19-yl 4-(dimethylamino)butanoate (MC3), 1,1′-(2-(4-(2-((2-(bis(2-hydroxydodecyl)amino)ethyl)(2-hydroxydodecyl)amino)ethyl)piperazin-1-yl)ethylazanediyl)didodecan-2-ol (Tech G1), or a mixture thereof. The cationic lipid can comprise from about 20 mol % to about 50 mol % or about 40 mol % of the total lipid present in the particle. 
     In some embodiments, the compound 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]-dioxolane can be used to prepare lipid-siRNA nanoparticles. 
     In some embodiments, the lipid-siRNA particle includes 40% 2, 2-Dilinoleyl-4-dimethylaminoethyl-[1,3]-dioxolane: 10% DSPC: 40% Cholesterol: 10% PEG-C-DOMG (mole percent) with a particle size of 63.0±20 nm and a 0.027 siRNA/Lipid Ratio. 
     The ionizable/non-cationic lipid can be an anionic lipid or a neutral lipid including, but not limited to, distearoylphosphatidylcholine (DSPC), dioleoylphosphatidylcholine (DOPC), dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylglycerol (DOPG), dipalmitoylphosphatidylglycerol (DPPG), dioleoyl-phosphatidylethanolamine (DOPE), palmitoyloleoylphosphatidylcholine (POPC), palmitoyloleoylphosphatidylethanolamine (POPE), dioleoyl-phosphatidylethanolamine 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (DOPE-mal), dipalmitoyl phosphatidyl ethanolamine (DPPE), dimyristoylphosphoethanolamine (DMPE), distearoyl-phosphatidyl-ethanolamine (DSPE), 16-O-monomethyl PE, 16-O-dimethyl PE, 18-1-trans PE, 1-stearoyl-2-oleoyl-phosphatidyethanolamine (SOPE), cholesterol, or a mixture thereof. The non-cationic lipid can be from about 5 mol % to about 90 mol %, about 10 mol %, or about 58 mol % if cholesterol is included, of the total lipid present in the particle. 
     The conjugated lipid that inhibits aggregation of particles can be, for example, a polyethyleneglycol (PEG)-lipid including, without limitation, a PEG-diacylglycerol (DAG), a PEG-dialkyloxypropyl (DAA), a PEG-phospholipid, a PEG-ceramide (Cer), or a mixture thereof. The PEG-DAA conjugate can be, for example, a PEG-dilauryloxypropyl (Ci 2 ), a PEG-dimyristyloxypropyl (Ci 4 ), a PEG-dipalmityloxypropyl (Ci 6 ), or a PEG-distearyloxypropyl (C] 8 ). The conjugated lipid that prevents aggregation of particles can be from 0 mol % to about 20 mol % or about 2 mol % of the total lipid present in the particle. 
     In some embodiments, the nucleic acid-lipid particle further includes cholesterol at, e.g., about 10 mol % to about 60 mol % or about 48 mol % of the total lipid present in the particle. 
     In one embodiment, the lipidoid ND98.4HCl (MW 1487) (see US20090023673, which is incorporated herein by reference), Cholesterol (Sigma-Aldrich), and PEG-Ceramide C16 (Avanti Polar Lipids) can be used to prepare lipid-dsRNA nanoparticles (i.e., LNP01 particles). Stock solutions of each in ethanol can be prepared as follows: ND98, 133 mg/ml; Cholesterol, 25 mg/ml, PEG-Ceramide C16, 100 mg/ml. The ND98, Cholesterol, and PEG-Ceramide C16 stock solutions can then be combined in a, e.g., 42:48:10 molar ratio. The combined lipid solution can be mixed with aqueous dsRNA (e.g., in sodium acetate pH 5) such that the final ethanol concentration is about 35-45% and the final sodium acetate concentration is about 100-300 mM. Lipid-dsRNA nanoparticles typically form spontaneously upon mixing. Depending on the desired particle size distribution, the resultant nanoparticle mixture can be extruded through a polycarbonate membrane (e.g., 100 nm cut-off) using, for example, a thermobarrel extruder, such as Lipex Extruder (Northern Lipids, Inc). In some cases, the extrusion step can be omitted. Ethanol removal and simultaneous buffer exchange can be accomplished by, for example, dialysis or tangential flow filtration. Buffer can be exchanged with, for example, phosphate buffered saline (PBS) at about pH 7, e.g., about pH 6.9, about pH 7.0, about pH 7.1, about pH 7.2, about pH 7.3, or about pH 7.4. 
     
       
         
         
             
             
         
       
     
     LNP01 formulations are described, e.g., in International Application Publication No. WO 2008/042973, which is hereby incorporated by reference. 
     Additional exemplary lipid-dsRNA formulations are described in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Exemplary lipid formulations 
               
            
           
           
               
               
               
            
               
                   
                   
                 cationic lipid/non-cationic 
               
               
                   
                   
                 lipid/cholesterol/PEG-lipid conjugate 
               
               
                   
                 Ionizable/Cationic Lipid 
                 Lipid:siRNA ratio 
               
               
                   
               
               
                 SNALP-1 
                 1,2-Dilinolenyloxy-N,N- 
                 DLinDMA/DPPC/Cholesterol/PEG-cDMA 
               
               
                   
                 dimethylaminopropane (DLinDMA) 
                 (57.1/7.1/34.4/1.4) 
               
               
                   
                   
                 lipid:siRNA~7:1 
               
               
                 2-XTC 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DPPC/Cholesterol/PEG-cDMA 
               
               
                   
                 dioxolane (XTC) 
                 57.1/7.1/34.4/1.4 
               
               
                   
                   
                 lipid:siRNA~7:1 
               
               
                 LNP05 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 dioxolane (XTC) 
                 57.5/7.5/31.5/3.5 
               
               
                   
                   
                 lipid:siRNA~6:1 
               
               
                 LNP06 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 dioxolane (XTC) 
                 57.5/7.5/31.5/3.5 
               
               
                   
                   
                 lipid:siRNA~11:1 
               
               
                 LNP07 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 dioxolane (XTC) 
                 60/7.5/31/1.5, 
               
               
                   
                   
                 lipid:siRNA~6:1 
               
               
                 LNP08 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 dioxolane (XTC) 
                 60/7.5/31/1.5, 
               
               
                   
                   
                 lipid:siRNA~11:1 
               
               
                 LNP09 
                 2,2-Dilinoleyl-4-dimethylaminoethyl-[1,3]- 
                 XTC/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 dioxolane (XTC) 
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA 10:1 
               
               
                 LNP10 
                 (3aR,5s,6aS)-N,N-dimethyl-2,2- 
                 ALN100/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 di((9Z,12Z)-octadeca-9,12- 
                 50/10/38.5/1.5 
               
               
                   
                 dienyl)tetrahydro-3aH- 
                 Lipid:siRNA 10:1 
               
               
                   
                 cyclopenta[d][1,3]dioxol-5-amine 
                   
               
               
                   
                 (ALN100) 
                   
               
               
                 LNP11 
                 (6Z,9Z,28Z,31Z)-heptatriaconta-6,9,28,31- 
                 MC-3/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 tetraen-19-yl 4-(dimethylamino)butanoate 
                 50/10/38.5/1.5 
               
               
                   
                 (MC3) 
                 Lipid:siRNA 10:1 
               
               
                 LNP12 
                 1,1′-(2-(4-(24(2-(bis(2- 
                 Tech Gl/DSPC/Cholesterol/PEG-DMG 
               
               
                   
                 hydroxydodecyDamino)ethyl)(2- 
                 50/10/38.5/1.5 
               
               
                   
                 hydroxydodecyl)amino)ethyl)piperazin-1- 
                 Lipid:siRNA 10:1 
               
               
                   
                 yl)ethylazanediyl)didodecan-2-ol (Tech G1) 
                   
               
               
                 LNP13 
                 XTC 
                 XTC/DSPC/Chol/PEG-DMG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 33:1 
               
               
                 LNP14 
                 MC3 
                 MC3/DSPC/Chol/PEG-DMG 
               
               
                   
                   
                 40/15/40/5 
               
               
                   
                   
                 Lipid:siRNA: 11:1 
               
               
                 LNP15 
                 MC3 
                 MC3/DSPC/Chol/PEG-DSG/GalNAc-PEG-DSG 
               
               
                   
                   
                 50/10/35/4.5/0.5 
               
               
                   
                   
                 Lipid:siRNA: 11:1 
               
               
                 LNP16 
                 MC3 
                 MC3/DSPC/Chol/PEG-DMG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 7:1 
               
               
                 LNP17 
                 MC3 
                 MC3/DSPC/Chol/PEG-DSG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 10:1 
               
               
                 LNP18 
                 MC3 
                 MC3/DSPC/Chol/PEG-DMG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 12:1 
               
               
                 LNP19 
                 MC3 
                 MC3/DSPC/Chol/PEG-DMG 
               
               
                   
                   
                 50/10/35/5 
               
               
                   
                   
                 Lipid:siRNA: 8:1 
               
               
                 LNP20 
                 MC3 
                 MC3/DSPC/Chol/PEG-DPG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 10:1 
               
               
                 LNP21 
                 C12-200 
                 C12-200/DSPC/Chol/PEG-DSG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 7:1 
               
               
                 LNP22 
                 XTC 
                 XTC/DSPC/Chol/PEG-DSG 
               
               
                   
                   
                 50/10/38.5/1.5 
               
               
                   
                   
                 Lipid:siRNA: 10:1 
               
               
                   
               
               
                 DSPC: distearoylphosphatidylcholine 
               
               
                 DPPC: dipalmitoylphosphatidylcholine 
               
               
                 PEG-DMG: PEG-didimyristoyl glycerol (C14-PEG, or PEG-C14) (PEG with avg mol wt of 2000) 
               
               
                 PEG-DSG: PEG-distyryl glycerol (C18-PEG, or PEG-C18) (PEG with avg mol wt of 2000) 
               
               
                 PEG-cDMA: PEG-carbamoyl-1,2-dimyristyloxypropylamine (PEG with avg mol wt of 2000) 
               
               
                 SNALP (1,2-Dilinolenyloxy-N,N-dimethylaminopropane (DLinDMA)) comprising formulations are described in International Publication No. WO 2009/127060, the entire contents of which is hereby incorporated herein by reference. 
               
               
                 XTC comprising formulations are described, e.g., in PCT Publication No. WO 2010/088537, the entire contents of which is hereby incorporated herein by reference. 
               
               
                 MC3 comprising formulations are described, e.g., in US Patent Publication No. 2010/0324120, filed Jun. 10, 2010, the entire contents of which are hereby incorporated by reference. 
               
               
                 ALNY-100 comprising formulations are described, e.g., PCT Publication No, WO 2010/054406, the entire contents of which are hereby incorporated herein by reference. 
               
               
                 C12-200 comprising formulations are described in PCT Publication No, WO 2010/129709, the entire contents of which are hereby incorporated herein by reference. 
               
            
           
         
       
     
     i. Synthesis of Ionizable/Cationic Lipids 
     Any of the compounds, e.g., cationic lipids and the like, used in the nucleic acid-lipid particles of the invention can be prepared by known organic synthesis techniques. 
     Formulations prepared by either the standard or extrusion-free method can be characterized in similar manners. For example, formulations are typically characterized by visual inspection. They should be whitish translucent solutions free from aggregates or sediment. Particle size and particle size distribution of lipid-nanoparticles can be measured by light scattering using, for example, a Malvern Zetasizer Nano ZS (Malvern, USA). Particles should be about 20-300 nm, such as 40-100 nm in size. The particle size distribution should be unimodal. The total dsRNA concentration in the formulation, as well as the entrapped fraction, is estimated using a dye exclusion assay. A sample of the formulated dsRNA can be incubated with an RNA-binding dye, such as Ribogreen (Molecular Probes) in the presence or absence of a formulation disrupting surfactant, e.g., 0.5% Triton®-X100. The total dsRNA in the formulation can be determined by the signal from the sample containing the surfactant, relative to a standard curve. The entrapped fraction is determined by subtracting the “free” dsRNA content (as measured by the signal in the absence of surfactant) from the total dsRNA content. Percent entrapped dsRNA is typically &gt;85%. For SNALP formulation, the particle size is at least 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, or 120 nm. The suitable range is typically 50 nm to 110 nm, 60 nm to 100 nm, or 80 nm to 90 nm. 
     Compositions and formulations for oral administration include powders or granules, microparticulates, nanoparticulates, suspensions, or solutions in water or non-aqueous media, capsules, gel capsules, sachets, tablets or minitablets. Thickeners, flavoring agents, diluents, emulsifiers, dispersing aids, or binders can be desirable. In some embodiments, oral formulations are those in which dsRNAs featured in the invention are administered in conjunction with one or more penetration enhancer surfactants and chelators. Suitable surfactants include fatty acids or esters or salts thereof, bile acids or salts thereof. Suitable bile acids/salts include chenodeoxycholic acid (CDCA) and ursodeoxychenodeoxycholic acid (UDCA), cholic acid, dehydrocholic acid, deoxycholic acid, glucholic acid, glycholic acid, glycodeoxycholic acid, taurocholic acid, taurodeoxycholic acid, sodium tauro-24,25-dihydro-fusidate and sodium glycodihydrofusidate. Suitable fatty acids include arachidonic acid, undecanoic acid, oleic acid, lauric acid, caprylic acid, capric acid, myristic acid, palmitic acid, stearic acid, linoleic acid, linolenic acid, dicaprate, tricaprate, monoolein, dilaurin, glyceryl 1-monocaprate, 1-dodecylazacycloheptan-2-one, an acylcarnitine, an acylcholine, or a monoglyceride, a diglyceride or a pharmaceutically acceptable salt thereof (e.g., sodium). In some embodiments, combinations of penetration enhancers are used, for example, fatty acids/salts in combination with bile acids/salts. One exemplary combination is the sodium salt of lauric acid, capric acid and UDCA. Further penetration enhancers include polyoxyethylene-9-lauryl ether, polyoxyethylene-20-cetyl ether. DsRNAs featured in the invention can be delivered orally, in granular form including sprayed dried particles, or complexed to form micro or nanoparticles. DsRNA complexing agents include poly-amino acids; polyimines; polyacrylates; polyalkylacrylates, polyoxethanes, polyalkylcyanoacrylates; cationized gelatins, albumins, starches, acrylates, polyethyleneglycols (PEG), and starches; polyalkylcyanoacrylates; DEAE-derivatized polyimines, pollulans, celluloses, and starches. Suitable complexing agents include chitosan, N-trimethylchitosan, poly-L-lysine, polyhistidine, polyornithine, polyspermines, protamine, polyvinylpyridine, polythiodiethylaminomethylethylene P(TDAE), polyaminostyrene (e.g., p-amino), poly(methylcyanoacrylate), poly(ethylcyanoacrylate), poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(isohexylcynaoacrylate), DEAE-methacrylate, DEAE-hexylacrylate, DEAE-acrylamide, DEAE-albumin and DEAE-dextran, polymethylacrylate, polyhexylacrylate, poly(D,L-lactic acid), poly(DL-lactic-co-glycolic acid (PLGA), alginate, and polyethyleneglycol (PEG). Oral formulations for dsRNAs and their preparation are described in detail in U.S. Pat. No. 6,887,906, US Publn. No. 20030027780, and U.S. Pat. No. 6,747,014, each of which is incorporated herein by reference. 
     Compositions and formulations for parenteral, intraparenchymal (into the brain), intrathecal, intraventricular, or intrahepatic administration can include sterile aqueous solutions which can also contain buffers, diluents, and other suitable additives such as, but not limited to, penetration enhancers, carrier compounds, and other pharmaceutically acceptable carriers or excipients. 
     Pharmaceutical compositions of the present invention include, but are not limited to, solutions, emulsions, and liposome-containing formulations. These compositions can be generated from a variety of components that include, but are not limited to, preformed liquids, self-emulsifying solids, and self-emulsifying semisolids. Formulations include those that target the liver when treating hepatic disorders such as hepatic carcinoma. 
     The pharmaceutical formulations of the present invention, which can conveniently be presented in unit dosage form, can be prepared according to conventional techniques well known in the pharmaceutical industry. Such techniques include the step of bringing into association the active ingredients with the pharmaceutical carrier(s) or excipient(s). In general, the formulations are prepared by uniformly and intimately bringing into association the active ingredients with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product. 
     The compositions of the present invention can be formulated into any of many possible dosage forms such as, but not limited to, tablets, capsules, gel capsules, liquid syrups, soft gels, suppositories, and enemas. The compositions of the present invention can also be formulated as suspensions in aqueous, non-aqueous or mixed media. Aqueous suspensions can further contain substances which increase the viscosity of the suspension including, for example, sodium carboxymethylcellulose, sorbitol, or dextran. The suspension can also contain stabilizers. 
     C. Additional Formulations 
     i. Emulsions 
     The iRNAs of the present invention can be prepared and formulated as emulsions. Emulsions are typically heterogeneous systems of one liquid dispersed in another in the form of droplets usually exceeding 0.1 μm in diameter (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 199; Rosoff, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., Volume 1, p. 245; Block in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 2, p. 335; Higuchi et al., in Remington&#39;s Pharmaceutical Sciences, Mack Publishing Co., Easton, Pa., 1985, p. 301). Emulsions are often biphasic systems comprising two immiscible liquid phases intimately mixed and dispersed with each other. In general, emulsions can be of either the water-in-oil (w/o) or the oil-in-water (o/w) variety. When an aqueous phase is finely divided into and dispersed as minute droplets into a bulk oily phase, the resulting composition is called a water-in-oil (w/o) emulsion. Alternatively, when an oily phase is finely divided into and dispersed as minute droplets into a bulk aqueous phase, the resulting composition is called an oil-in-water (o/w) emulsion. Emulsions can contain additional components in addition to the dispersed phases, and the active drug which can be present as a solution either in the aqueous phase, oily phase or itself as a separate phase. Pharmaceutical excipients such as emulsifiers, stabilizers, dyes, and anti-oxidants can also be present in emulsions as needed. Pharmaceutical emulsions can also be multiple emulsions that are comprised of more than two phases such as, for example, in the case of oil-in-water-in-oil (o/w/o) and water-in-oil-in-water (w/o/w) emulsions. Such complex formulations often provide certain advantages that simple binary emulsions do not. Multiple emulsions in which individual oil droplets of an o/w emulsion enclose small water droplets constitute a w/o/w emulsion. Likewise a system of oil droplets enclosed in globules of water stabilized in an oily continuous phase provides an o/w/o emulsion. 
     Emulsions are characterized by little or no thermodynamic stability. Often, the dispersed or discontinuous phase of the emulsion is well dispersed into the external or continuous phase and maintained in this form through the means of emulsifiers or the viscosity of the formulation. Either of the phases of the emulsion can be a semisolid or a solid, as is the case of emulsion-style ointment bases and creams. Other means of stabilizing emulsions entail the use of emulsifiers that can be incorporated into either phase of the emulsion. Emulsifiers can broadly be classified into four categories: synthetic surfactants, naturally occurring emulsifiers, absorption bases, and finely dispersed solids (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp;  Wilkins  (8th ed.), New York, N.Y.; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 199). 
     Synthetic surfactants, also known as surface active agents, have found wide applicability in the formulation of emulsions and have been reviewed in the literature (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Rieger, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 285; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), Marcel Dekker, Inc., New York, N.Y., 1988, volume 1, p. 199). Surfactants are typically amphiphilic and comprise a hydrophilic and a hydrophobic portion. The ratio of the hydrophilic to the hydrophobic nature of the surfactant has been termed the hydrophile/lipophile balance (HLB) and is a valuable tool in categorizing and selecting surfactants in the preparation of formulations. Surfactants can be classified into different classes based on the nature of the hydrophilic group: nonionic, anionic, cationic, and amphoteric (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y. Rieger, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 285). 
     Naturally occurring emulsifiers used in emulsion formulations include lanolin, beeswax, phosphatides, lecithin, and acacia. Absorption bases possess hydrophilic properties such that they can soak up water to form w/o emulsions yet retain their semisolid consistencies, such as anhydrous lanolin and hydrophilic petrolatum. Finely divided solids have also been used as good emulsifiers especially in combination with surfactants and in viscous preparations. These include polar inorganic solids, such as heavy metal hydroxides, nonswelling clays such as bentonite, attapulgite, hectorite, kaolin, montmorillonite, colloidal aluminum silicate, and colloidal magnesium aluminum silicate, pigments and nonpolar solids such as carbon or glyceryl tristearate. 
     A large variety of non-emulsifying materials are also included in emulsion formulations and contribute to the properties of emulsions. These include fats, oils, waxes, fatty acids, fatty alcohols, fatty esters, humectants, hydrophilic colloids, preservatives, and antioxidants (Block, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 335; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 199). 
     Hydrophilic colloids or hydrocolloids include naturally occurring gums and synthetic polymers such as polysaccharides (for example, acacia, agar, alginic acid, carrageenan, guar gum, karaya gum, and tragacanth), cellulose derivatives (for example, carboxymethylcellulose and carboxypropylcellulose), and synthetic polymers (for example, carbomers, cellulose ethers, and carboxyvinyl polymers). These disperse or swell in water to form colloidal solutions that stabilize emulsions by forming strong interfacial films around the dispersed-phase droplets and by increasing the viscosity of the external phase. 
     Since emulsions often contain a number of ingredients such as carbohydrates, proteins, sterols and phosphatides that can readily support the growth of microbes, these formulations often incorporate preservatives. Commonly used preservatives included in emulsion formulations include methyl paraben, propyl paraben, quaternary ammonium salts, benzalkonium chloride, esters of p-hydroxybenzoic acid, and boric acid. Antioxidants are also commonly added to emulsion formulations to prevent deterioration of the formulation. Antioxidants used can be free radical scavengers such as tocopherols, alkyl gallates, butylated hydroxyanisole, butylated hydroxytoluene, or reducing agents such as ascorbic acid and sodium metabisulfite, and antioxidant synergists such as citric acid, tartaric acid, and lecithin. 
     The application of emulsion formulations via dermatological, oral, and parenteral routes, and methods for their manufacture have been reviewed in the literature (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 199). Emulsion formulations for oral delivery have been very widely used because of ease of formulation, as well as efficacy from an absorption and bioavailability standpoint (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Rosoff, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 245; Idson, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 199). Mineral-oil base laxatives, oil-soluble vitamins, and high fat nutritive preparations are among the materials that have commonly been administered orally as o/w emulsions. 
     ii. Microemulsions 
     In one embodiment of the present invention, the iRNAs are formulated as microemulsions. A microemulsion can be defined as a system of water, oil, and amphiphile which is a single optically isotropic and thermodynamically stable liquid solution (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Rosoff, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 245). Typically microemulsions are systems that are prepared by first dispersing an oil in an aqueous surfactant solution and then adding a sufficient amount of a fourth component, generally an intermediate chain-length alcohol to form a transparent system. Therefore, microemulsions have also been described as thermodynamically stable, isotropically clear dispersions of two immiscible liquids that are stabilized by interfacial films of surface-active molecules (Leung and Shah, in: Controlled Release of Drugs: Polymers and Aggregate Systems, Rosoff, M., Ed., 1989, VCH Publishers, New York, pages 185-215). Microemulsions commonly are prepared via a combination of three to five components that include oil, water, surfactant, cosurfactant and electrolyte. Whether the microemulsion is of the water-in-oil (w/o) or an oil-in-water (o/w) type is dependent on the properties of the oil and surfactant used and on the structure and geometric packing of the polar heads and hydrocarbon tails of the surfactant molecules (Schott, in Remington&#39;s Pharmaceutical Sciences, Mack Publishing Co., Easton, Pa., 1985, p. 271). 
     The phenomenological approach utilizing phase diagrams has been extensively studied and has yielded a comprehensive knowledge, to one skilled in the art, of how to formulate microemulsions (see e.g., Ansel&#39;s Pharmaceutical Dosage Forms and Drug Delivery Systems, Allen, L V., Popovich N G., and Ansel H C., 2004, Lippincott Williams &amp; Wilkins (8th ed.), New York, N.Y.; Rosoff, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 245; Block, in Pharmaceutical Dosage Forms, Lieberman, Rieger and Banker (Eds.), 1988, Marcel Dekker, Inc., New York, N.Y., volume 1, p. 335). Compared to conventional emulsions, microemulsions offer the advantage of solubilizing water-insoluble drugs in a formulation of thermodynamically stable droplets that are formed spontaneously. 
     Surfactants used in the preparation of microemulsions include, but are not limited to, ionic surfactants, non-ionic surfactants, Brij® 96, polyoxyethylene oleyl ethers, polyglycerol fatty acid esters, tetraglycerol monolaurate (ML310), tetraglycerol monooleate (M0310), hexaglycerol monooleate (P0310), hexaglycerol pentaoleate (P0500), decaglycerol monocaprate (MCA750), decaglycerol monooleate (M0750), decaglycerol sequioleate (S0750), decaglycerol decaoleate (DA0750), alone or in combination with cosurfactants. The cosurfactant, usually a short-chain alcohol such as ethanol, 1-propanol, and 1-butanol, serves to increase the interfacial fluidity by penetrating into the surfactant film and consequently creating a disordered film because of the void space generated among surfactant molecules. Microemulsions can, however, be prepared without the use of cosurfactants and alcohol-free self-emulsifying microemulsion systems are known in the art. The aqueous phase can typically be, but is not limited to, water, an aqueous solution of the drug, glycerol, PEG300, PEG400, polyglycerols, propylene glycols, and derivatives of ethylene glycol. The oil phase can include, but is not limited to, materials such as Captex® 300, Captex® 355, Capmul® MCM, fatty acid esters, medium chain (C8-C12) mono, di, and tri-glycerides, polyoxyethylated glyceryl fatty acid esters, fatty alcohols, polyglycolized glycerides, saturated polyglycolized C8-C10 glycerides, vegetable oils, and silicone oil. 
     Microemulsions are particularly of interest from the standpoint of drug solubilization and the enhanced absorption of drugs. Lipid based microemulsions (both o/w and w/o) have been proposed to enhance the oral bioavailability of drugs, including peptides (see e.g., U.S. Pat. Nos. 6,191,105; 7,063,860; 7,070,802; 7,157,099; Constantinides et al., Pharmaceutical Research, 1994, 11, 1385-1390; Ritschel, Meth. Find. Exp. Clin. Pharmacol., 1993, 13, 205). Microemulsions afford advantages of improved drug solubilization, protection of drug from enzymatic hydrolysis, possible enhancement of drug absorption due to surfactant-induced alterations in membrane fluidity and permeability, ease of preparation, ease of oral administration over solid dosage forms, improved clinical potency, and decreased toxicity (see e.g., U.S. Pat. Nos. 6,191,105; 7,063,860; 7,070,802; 7,157,099; Constantinides et al., Pharmaceutical Research, 1994, 11, 1385; Ho et al., J. Pharm. Sci., 1996, 85, 138-143). Often microemulsions can form spontaneously when their components are brought together at ambient temperature. This can be particularly advantageous when formulating thermolabile drugs, peptides or iRNAs. Microemulsions have also been effective in the transdermal delivery of active components in both cosmetic and pharmaceutical applications. It is expected that the microemulsion compositions and formulations of the present invention will facilitate the increased systemic absorption of iRNAs and nucleic acids from the gastrointestinal tract, as well as improve the local cellular uptake of iRNAs and nucleic acids. 
     Microemulsions of the present invention can also contain additional components and additives such as sorbitan monostearate (Grill® 3), Labrasol®, and penetration enhancers to improve the properties of the formulation and to enhance the absorption of the iRNAs and nucleic acids of the present invention. Penetration enhancers used in the microemulsions of the present invention can be classified as belonging to one of five broad categories—surfactants, fatty acids, bile salts, chelating agents, and non-chelating non-surfactants (Lee et al., Critical Reviews in Therapeutic Drug Carrier Systems, 1991, p. 92). Each of these classes has been discussed above. 
     iii. Microparticles 
     An iRNA of the invention may be incorporated into a particle, e.g., a microparticle. Microparticles can be produced by spray-drying, but may also be produced by other methods including lyophilization, evaporation, fluid bed drying, vacuum drying, or a combination of these techniques. 
     iv. Penetration Enhancers 
     In one embodiment, the present invention employs various penetration enhancers to effect the efficient delivery of nucleic acids, particularly iRNAs, to the skin of animals. Most drugs are present in solution in both ionized and nonionized forms. However, usually only lipid soluble or lipophilic drugs readily cross cell membranes. It has been discovered that even non-lipophilic drugs can cross cell membranes if the membrane to be crossed is treated with a penetration enhancer. In addition to aiding the diffusion of non-lipophilic drugs across cell membranes, penetration enhancers also enhance the permeability of lipophilic drugs. 
     Penetration enhancers can be classified as belonging to one of five broad categories, i.e., surfactants, fatty acids, bile salts, chelating agents, and non-chelating non-surfactants (see e.g., Malmsten, M. Surfactants and polymers in drug delivery, Informa Health Care, New York, N.Y., 2002; Lee et al., Critical Reviews in Therapeutic Drug Carrier Systems, 1991, p. 92). Such compounds are well known in the art. 
     v. Carriers 
     Certain compositions of the present invention also incorporate carrier compounds in the formulation. As used herein, “carrier compound” or “carrier” can refer to a nucleic acid, or analog thereof, which is inert (i.e., does not possess biological activity per se) but is recognized as a nucleic acid by in vivo processes that reduce the bioavailability of a nucleic acid having biological activity by, for example, degrading the biologically active nucleic acid or promoting its removal from circulation. The coadministration of a nucleic acid and a carrier compound, typically with an excess of the latter substance, can result in a substantial reduction of the amount of nucleic acid recovered in the liver, kidney or other extracirculatory reservoirs, presumably due to competition between the carrier compound and the nucleic acid for a common receptor. For example, the recovery of a partially phosphorothioate dsRNA in hepatic tissue can be reduced when it is coadministered with polyinosinic acid, dextran sulfate, polycytidic acid or 4-acetamido-4′isothiocyano-stilbene-2,2′-disulfonic acid (Miyao et al., DsRNA Res. Dev., 1995, 5, 115-121; Takakura et al., DsRNA &amp; Nucl. Acid Drug Dev., 1996, 6, 177-183. 
     vi. Excipients 
     In contrast to a carrier compound, a “pharmaceutical carrier” or “excipient” is a pharmaceutically acceptable solvent, suspending agent, or any other pharmacologically inert vehicle for delivering one or more nucleic acids to an animal. The excipient can be liquid or solid and is selected, with the planned manner of administration in mind, so as to provide for the desired bulk, consistency, etc., when combined with a nucleic acid and the other components of a given pharmaceutical composition. Typical pharmaceutical carriers include, but are not limited to, binding agents (e.g., pregelatinized maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose, etc.); fillers (e.g., lactose and other sugars, microcrystalline cellulose, pectin, gelatin, calcium sulfate, ethyl cellulose, polyacrylates or calcium hydrogen phosphate, etc.); lubricants (e.g., magnesium stearate, talc, silica, colloidal silicon dioxide, stearic acid, metallic stearates, hydrogenated vegetable oils, corn starch, polyethylene glycols, sodium benzoate, sodium acetate, etc.); disintegrants (e.g., starch, sodium starch glycolate, etc.); and wetting agents (e.g., sodium lauryl sulphate, etc). 
     Pharmaceutically acceptable organic or inorganic excipients suitable for non-parenteral administration which do not deleteriously react with nucleic acids can also be used to formulate the compositions of the present invention. Suitable pharmaceutically acceptable carriers include, but are not limited to, water, salt solutions, alcohols, polyethylene glycols, gelatin, lactose, amylose, magnesium stearate, talc, silicic acid, viscous paraffin, hydroxymethylcellulose, polyvinylpyrrolidone, and the like. 
     Formulations for topical administration of nucleic acids can include sterile and non-sterile aqueous solutions, non-aqueous solutions in common solvents such as alcohols, or solutions of the nucleic acids in liquid or solid oil bases. The solutions can also contain buffers, diluents and other suitable additives. Pharmaceutically acceptable organic or inorganic excipients suitable for non-parenteral administration which do not deleteriously react with nucleic acids can be used. 
     Suitable pharmaceutically acceptable excipients include, but are not limited to, water, salt solutions, alcohol, polyethylene glycols, gelatin, lactose, amylose, magnesium stearate, talc, silicic acid, viscous paraffin, hydroxymethylcellulose, polyvinylpyrrolidone, and the like. 
     vii. Other Components 
     The compositions of the present invention can additionally contain other adjunct components conventionally found in pharmaceutical compositions, at their art-established usage levels. Thus, for example, the compositions can contain additional, compatible, pharmaceutically-active materials such as, for example, antipruritics, astringents, local anesthetics or anti-inflammatory agents, or can contain additional materials useful in physically formulating various dosage forms of the compositions of the present invention, such as dyes, flavoring agents, preservatives, antioxidants, opacifiers, thickening agents and stabilizers. However, such materials, when added, should not unduly interfere with the biological activities of the components of the compositions of the present invention. The formulations can be sterilized and, if desired, mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, colorings, flavorings and/or aromatic substances and the like which do not deleteriously interact with the nucleic acid(s) of the formulation. 
     Aqueous suspensions can contain substances which increase the viscosity of the suspension including, for example, sodium carboxymethylcellulose, sorbitol, or dextran. The suspension can also contain stabilizers. 
     In some embodiments, pharmaceutical compositions featured in the invention include (a) one or more iRNA and (b) one or more agents which function by a non-iRNA mechanism and which are useful in treating a PD-L1-associated disorder. 
     Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Compounds that exhibit high therapeutic indices are preferred. 
     The data obtained from cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of compositions featured herein in the invention lies generally within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage can vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the methods featured in the invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose can be formulated in animal models to achieve a circulating plasma concentration range of the compound or, when appropriate, of the polypeptide product of a target sequence (e.g., achieving a decreased concentration of the polypeptide) that includes the IC50 (i.e., the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma can be measured, for example, by high performance liquid chromatography. 
     In addition to their administration, as discussed above, the iRNAs featured in the invention can be administered in combination with other known agents effective in treatment of pathological processes mediated by PD-L1 expression. In any event, the administering physician can adjust the amount and timing of iRNA administration on the basis of results observed using standard measures of efficacy known in the art or described herein. 
     VI. Methods For Inhibiting PD-L1 Expression 
     The present invention also provides methods of inhibiting expression of a PD-L1 gene in a cell. The methods include contacting a cell with an RNAi agent, e.g., double stranded RNAi agent, in an amount effective to inhibit expression of PD-L1 in the cell, thereby inhibiting expression of PD-L1 in the cell. In certain embodiments of the invention, PD-L1 is inhibited preferentially in liver cells. 
     Contacting of a cell with an iRNA, e.g., a double stranded RNAi agent, may be done in vitro or in vivo. Contacting a cell in vivo with the iRNA includes contacting a cell or group of cells within a subject, e.g., a human subject, with the iRNA. Combinations of in vitro and in vivo methods of contacting a cell are also possible. Contacting a cell may be direct or indirect, as discussed above. Furthermore, contacting a cell may be accomplished via a targeting ligand, including any ligand described herein or known in the art. In preferred embodiments, the targeting ligand is a carbohydrate moiety, e.g., a GalNAc 3  ligand, or any other ligand that directs the RNAi agent to a site of interest. 
     The term “inhibiting,” as used herein, is used interchangeably with “reducing,” “silencing,” “downregulating”, “suppressing”, and other similar terms, and includes any level of inhibition. 
     The phrase “inhibiting expression of a PD-L1” is intended to refer to inhibition of expression of any PD-L1 gene (such as, e.g., a mouse PD-L1 gene, a rat PD-L1 gene, a monkey PD-L1 gene, or a human PD-L1 gene) as well as variants or mutants of a PD-L1 gene. Thus, the PD-L1 gene may be a wild-type PD-L1 gene, a mutant PD-L1 gene, or a transgenic PD-L1 gene in the context of a genetically manipulated cell, group of cells, or organism. 
     “Inhibiting expression of a PD-L1 gene” includes any level of inhibition of a PD-L1 gene, e.g., at least partial suppression of the expression of a PD-L1 gene. The expression of the PD-L1 gene may be assessed based on the level, or the change in the level, of any variable associated with PD-L1 gene expression, e.g., PD-L1 mRNA level or PD-L1 protein level. This level may be assessed in an individual cell or in a group of cells, including, for example, a sample derived from a subject. It is understood that expression of PD-L1 may be near or below the level of detection in a normal subject in many cell types and body fluids. Therefore, the inhibition of expression of PD-L1 for example, can compare the level of PD-L1 in the liver of a subject infected with a hepatitis virus prior to and after treatment with an agent for the inhibition of PD-L1 or in a tumor before or after treatment with an agent for inhibition of PD-L1. 
     In certain embodiments, surrogate markers can be used to detect inhibition of PD-L1. For example, effective treatment of an infection, e.g., a hepatitis virus infection as demonstrated by acceptable diagnostic and monitoring criteria with an agent to reduce PD-L1 expression can be understood to demonstrate a clinically relevant reduction in PD-L1. Stabilization or reduction of tumor burden in a subject with cancer as determined by RECIST criteria after treatment with an agent to reduce PD-L1 can be understood to demonstrate a clinically relevant reduction in PD-L1. 
     Inhibition may be assessed by a decrease in an absolute or relative level of one or more variables that are associated with PD-L1 expression compared with a control level. The control level may be any type of control level that is utilized in the art, e.g., a pre-dose baseline level, or a level determined from a similar subject (e.g., historical control), cell, or sample that is untreated or treated with a control (such as, e.g., buffer only control or inactive agent control). 
     In some embodiments of the methods of the invention, expression of a PD-L1 gene is inhibited by at least 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, or to below the level of detection of the assay. In certain embodiments, the methods include a clinically relevant inhibition of expression of PD-L1, e.g. as demonstrated by a clinically relevant outcome after treatment of a subject with an agent to reduce the expression of PD-L1. 
     Inhibition of the expression of a PD-L1 gene may be manifested by a reduction of the amount of mRNA expressed by a first cell or group of cells (such cells may be present, for example, in a sample derived from a subject) in which a PD-L1 gene is transcribed and which has or have been treated (e.g., by contacting the cell or cells with an iRNA of the invention, or by administering an iRNA of the invention to a subject in which the cells are or were present) such that the expression of a PD-L1 gene is inhibited, as compared to a second cell or group of cells substantially identical to the first cell or group of cells but which has not or have not been so treated (control cell(s) not treated with an iRNA or not treated with an iRNA targeted to the gene of interest). In preferred embodiments, the inhibition is assessed by the method provided in Example 2 in the RKO human colon carcinoma cells treated with 10 nM iRNA and expressing the level of mRNA in treated cells as a percentage of the level of mRNA in control cells, using the following formula: 
     
       
         
           
             
               
                 
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     In other embodiments, inhibition of the expression of a PD-L1 gene may be assessed in terms of a reduction of a parameter that is functionally linked to PD-L1 gene expression, e.g., PD-L1 protein expression or PD-L1 signaling pathways. PD-L1 gene silencing may be determined in any cell expressing PD-L1, either endogenous or heterologous from an expression construct, and by any assay known in the art. 
     Inhibition of the expression of a PD-L1 protein may be manifested by a reduction in the level of the PD-L1 protein that is expressed by a cell or group of cells (e.g., the level of protein expressed in a sample derived from a subject). As explained above, for the assessment of mRNA suppression, the inhibition of protein expression levels in a treated cell or group of cells may similarly be expressed as a percentage of the level of protein in a control cell or group of cells. 
     A control cell or group of cells that may be used to assess the inhibition of the expression of a PD-L1 gene includes a cell or group of cells that has not yet been contacted with an RNAi agent of the invention. For example, the control cell or group of cells may be derived from an individual subject (e.g., a human or animal subject) prior to treatment of the subject with an RNAi agent. 
     The level of PD-L1 mRNA that is expressed by a cell or group of cells may be determined using any method known in the art for assessing mRNA expression. In one embodiment, the level of expression of PD-L1 in a sample is determined by detecting a transcribed polynucleotide, or portion thereof, e.g., mRNA of the PD-L1 gene. RNA may be extracted from cells using RNA extraction techniques including, for example, using acid phenol/guanidine isothiocyanate extraction (RNAzol B; Biogenesis), RNeasy™ RNA preparation kits (Qiagen®) or PAXgene (PreAnalytix, Switzerland). Typical assay formats utilizing ribonucleic acid hybridization include nuclear run-on assays, RT-PCR, RNase protection assays, northern blotting, in situ hybridization, and microarray analysis. Circulating PD-L1 mRNA may be detected using methods the described in PCT Publication WO2012/177906, the entire contents of which are hereby incorporated herein by reference. 
     In some embodiments, the level of expression of PD-L1 is determined using a nucleic acid probe. The term “probe”, as used herein, refers to any molecule that is capable of selectively binding to a specific PD-L1. Probes can be synthesized by one of skill in the art, or derived from appropriate biological preparations. Probes may be specifically designed to be labeled. Examples of molecules that can be utilized as probes include, but are not limited to, RNA, DNA, proteins, antibodies, and organic molecules. 
     Isolated mRNA can be used in hybridization or amplification assays that include, but are not limited to, Southern or northern analyses, polymerase chain reaction (PCR) analyses and probe arrays. One method for the determination of mRNA levels involves contacting the isolated mRNA with a nucleic acid molecule (probe) that can hybridize to PD-L1 mRNA. In one embodiment, the mRNA is immobilized on a solid surface and contacted with a probe, for example by running the isolated mRNA on an agarose gel and transferring the mRNA from the gel to a membrane, such as nitrocellulose. In an alternative embodiment, the probe(s) are immobilized on a solid surface and the mRNA is contacted with the probe(s), for example, in an Affymetrix GeneChip® array. A skilled artisan can readily adapt known mRNA detection methods for use in determining the level of PD-L1 mRNA. 
     An alternative method for determining the level of expression of PD-L1 in a sample involves the process of nucleic acid amplification and/or reverse transcriptase (to prepare cDNA) of for example mRNA in the sample, e.g., by RT-PCR (the experimental embodiment set forth in Mullis, 1987, U.S. Pat. No. 4,683,202), ligase chain reaction (Barany (1991)  Proc. Natl. Acad. Sci. USA  88:189-193), self sustained sequence replication (Guatelli et al. (1990)  Proc. Natl. Acad. Sci. USA  87:1874-1878), transcriptional amplification system (Kwoh et al. (1989)  Proc. Natl. Acad. Sci. USA  86:1173-1177), Q-Beta Replicase (Lizardi et al. (1988)  Bio/Technology  6:1197), rolling circle replication (Lizardi et al., U.S. Pat. No. 5,854,033) or any other nucleic acid amplification method, followed by the detection of the amplified molecules using techniques well known to those of skill in the art. These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present in very low numbers. In particular aspects of the invention, the level of expression of PD-L1 is determined by quantitative fluorogenic RT-PCR (i.e., the TaqMan™ System) or the Dual-Glo® Luciferase assay in Example 2. 
     The expression levels of PD-L1 mRNA may be monitored using a membrane blot (such as used in hybridization analysis such as northern, Southern, dot, and the like), or microwells, sample tubes, gels, beads or fibers (or any solid support comprising bound nucleic acids). See U.S. Pat. Nos. 5,770,722, 5,874,219, 5,744,305, 5,677,195 and 5,445,934, which are incorporated herein by reference. The determination of PD-L1 expression level may also comprise using nucleic acid probes in solution. 
     In preferred embodiments, the level of mRNA expression is assessed using branched DNA (bDNA) assays or real time PCR (qPCR). The use of this PCR method is described and exemplified in the Examples presented herein. Such methods can also be used for the detection of pathogen nucleic acids, e.g., hepatitis virus nucleic acids. 
     The level of PD-L1 protein expression may be determined using any method known in the art for the measurement of protein levels. Such methods include, for example, electrophoresis, capillary electrophoresis, high performance liquid chromatography (HPLC), thin layer chromatography (TLC), hyperdiffusion chromatography, fluid or gel precipitin reactions, absorption spectroscopy, a colorimetric assays, spectrophotometric assays, flow cytometry, immunodiffusion (single or double), immunoelectrophoresis, western blotting, radioimmunoassay (RIA), enzyme-linked immunosorbent assays (ELISAs), immunofluorescent assays, electrochemiluminescence assays, and the like. Such assays can also be used for the detection of proteins indicative of the presence or replication of pathogens, e.g. viral proteins. 
     In some embodiments, the efficacy of the methods of the invention in the treatment of a PD-L1-related disease is assessed by a decrease in PD-L1 mRNA level (by liver biopsy). 
     In some embodiments, the efficacy of the methods of the invention in the treatment of HBV infection is monitored by evaluating combinations of serological markers as discussed below. Efficacy of treatment of subjects with HBV can be monitored by detecting the level of heptatitis B s antigen (HBsAg) or HBeAg in the subject, wherein a reduction in the level of HBsAg or HBeAg, e.g., in serum, is indicative of effective treatment of the disease. In preferred embodiments, the reduction in the level of HBsAg or HbeAg is clinically relevant, e.g., comparable to the level of reduction observed with the standard of care. Efficacy of treatment can also be determined by a clinically relevant reduction of the level of HBV DNA in the subject, e.g., comparable to the level of reduction observed with the standard of care, e.g., suppression by at least 4 log 10  IU/mL, preferably at least 5 log 10  IU/mL (Dienstag, Hepatology, 2009, 49:S112-S121). Efficacy of treatment can also be determined by the presence of anti-HBsAg antibodies. 
     In some embodiments, the efficacy of the method of the invention in treatment of cancer can be monitored by evaluating a subject for maintenance or preferably reduction of tumor burden of the primary tumor or metastatic tumor(s) or the prevention of metastasis. Methods for detection and monitoring of tumor burden are known in the art, e.g., RECIST criteria as provided in Eisenhauer et al., 2009, New response evaluation criteria in solid tumours: Revised RECIST guideline (version 1.1). Eur. J. Cancer. 45:228-247. 
     In some embodiments of the methods of the invention, the iRNA is administered to a subject such that the iRNA is delivered to a specific site within the subject. The inhibition of expression of PD-L1 may be assessed using measurements of the level or change in the level of PD-L1 mRNA or PD-L1 protein in a sample derived from a specific site within the subject, e.g., the liver. In certain embodiments, the methods include a clinically relevant inhibition of expression of PD-L1, e.g. as demonstrated by a clinically relevant outcome after treatment of a subject with an agent to reduce the expression of PD-L1. 
     As used herein, the terms detecting or determining a level of an anlyte are understood to mean performing the steps to determine if a material, e.g., protein, RNA, is present. As used herein, methods of detecting or determining include detection or determination of an anlyte level that is below the level of detection for the method used. 
     Animal models of PD-L1 associated diseases are well known in the art. For example, animal models of hepatitis B infection are known in the art including chimpanzee, woodchuck, and transgenic mouse models of HBV (Wieland, 2015 . Cold Spring Harb. Perspect. Med.,  5:a021469, 2015; Tennant and Gerin, 2001 . ILAR Journal,  42:89-102; and Moriyama et al., 1990 . Science,  248:361-364). The chimpanzee model may also be used as a model for hepatitis D infection. Comparative models of chronic vs. acute lymphocytic choriomeningitis virus (LCMV) infection are useful for the study of immune exhaustion (Matloubian et al., 1994 , J. Virol.  68:8056-8063). A large number of cancer models including PD-L1 expressing tumors are known in the art (Iwai et al., 2002 , PNAS,  99:12293-12297). 
     VII. Methods of Treating or Preventing PD-L1-Associated Diseases 
     The present invention also provides methods of using an iRNA of the invention or a composition containing an iRNA of the invention to reduce or inhibit PD-L1 expression in a cell. The methods include contacting the cell with a dsRNA of the invention and maintaining the cell for a time sufficient to obtain degradation of the mRNA transcript of a PD-L1 gene, thereby inhibiting expression of the PD-L1 gene in the cell. Reduction in gene expression can be assessed by any methods known in the art. For example, a reduction in the expression of PD-L1 may be determined by determining the mRNA expression level of PD-L1, e.g., in a liver sample, using methods routine to one of ordinary skill in the art, e.g., northern blotting, qRT-PCR, e.g., as provided in Example 2; by determining the protein level of PD-L1 using methods routine to one of ordinary skill in the art, such as western blotting, immunological techniques. A reduction in the expression of PD-L1 may also be assessed indirectly by measuring a decrease in biological activity of PD-L1 or measuring the level of PD-L1 in a subject sample (e.g., a serum sample). A reduction in the expression of PD-L1 can also be assessed indirectly by measuring or observing a change, preferably a clinically relevant change, in at least one sign or symptom of a PD-L1 associated disease. 
     In the methods of the invention the cell may be contacted in vitro or in vivo, i.e., the cell may be within a subject. 
     A cell suitable for treatment using the methods of the invention may be any cell that expresses a PD-L1 gene, typically a liver cell. A cell suitable for use in the methods of the invention may be a mammalian cell, e.g., a primate cell (such as a human cell or a non-human primate cell, e.g., a monkey cell or a chimpanzee cell), a non-primate cell (such as a cow cell, a pig cell, a camel cell, a llama cell, a horse cell, a goat cell, a rabbit cell, a sheep cell, a hamster, a guinea pig cell, a cat cell, a dog cell, a rat cell, a mouse cell, a lion cell, a tiger cell, a bear cell, or a buffalo cell), a bird cell (e.g., a duck cell or a goose cell), or a whale cell, when the target gene sequence has sufficient complementarity to the iRNA agent to promote target knockdown. In one embodiment, the cell is a human cell, e.g., a human liver cell. 
     PD-L1 expression is inhibited in the cell by at least 20%, 25%, preferably at least 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, or to a level below the level of detection of the assay. In certain embodiments, the methods include a clinically relevant inhibition of expression of PD-L1, e.g. as demonstrated by a clinically relevant outcome after treatment of a subject with an agent to reduce the expression of PD-L1. 
     The in vivo methods of the invention may include administering to a subject a composition containing an iRNA, where the iRNA includes a nucleotide sequence that is complementary to at least a part of an RNA transcript of the PD-L1 gene of the mammal to be treated. When the organism to be treated is a mammal such as a human, the composition can be administered by any means known in the art including, but not limited to oral, intraperitoneal, or parenteral routes, including intracranial (e.g., intraventricular, intraparenchymal, and intrathecal), intravenous, intramuscular, subcutaneous, transdermal, airway (aerosol), nasal, rectal, and topical (including buccal and sublingual) administration. In certain embodiments, the compositions are administered by intravenous infusion or injection. In certain embodiments, the compositions are administered by subcutaneous injection. 
     In some embodiments, the administration is via a depot injection. A depot injection may release the iRNA in a consistent way over a prolonged time period. Thus, a depot injection may reduce the frequency of dosing needed to obtain a desired effect, e.g., a desired inhibition of PD-L1, or a therapeutic effect. A depot injection may also provide more consistent serum concentrations. Depot injections may include subcutaneous injections or intramuscular injections. In preferred embodiments, the depot injection is a subcutaneous injection. 
     In some embodiments, the administration is via a pump. The pump may be an external pump or a surgically implanted pump. In certain embodiments, the pump is a subcutaneously implanted osmotic pump. In other embodiments, the pump is an infusion pump. An infusion pump may be used for intravenous, subcutaneous, arterial, or epidural infusions. In preferred embodiments, the infusion pump is a subcutaneous infusion pump. In other embodiments, the pump is a surgically implanted pump that delivers the iRNA to the liver. 
     The mode of administration may be chosen based upon whether local or systemic treatment is desired and based upon the area to be treated. The route and site of administration may be chosen to enhance targeting. 
     In one aspect, the present invention also provides methods for inhibiting the expression of a PD-L1 gene in a mammal. The methods include administering to the mammal a composition comprising a dsRNA that targets a PD-L1 gene in a cell of the mammal and maintaining the mammal for a time sufficient to obtain degradation of the mRNA transcript of the PD-L1 gene, thereby inhibiting expression of the PD-L1 gene in the cell. Reduction in gene expression can be assessed by any methods known it the art and by methods, e.g. qRT-PCR, described herein. Reduction in protein production can be assessed by any methods known it the art and by methods, e.g. ELISA, described herein. In one embodiment, a puncture liver biopsy sample serves as the tissue material for monitoring the reduction in the PD-L1 gene or protein expression. In certain embodiments, inhibition of PD-L1 expression is confirmed by observation of clinically relevant outcomes. 
     The present invention further provides methods of treatment of a subject in need thereof. The treatment methods of the invention include administering an iRNA of the invention to a subject, e.g., a subject that would benefit from a reduction or inhibition of PD-L1 expression, in a therapeutically effective amount of an iRNA targeting a PD-L1 gene or a pharmaceutical composition comprising an iRNA targeting a PD-L1 gene. 
     An iRNA of the invention may be administered as a “free iRNA.” A free iRNA is administered in the absence of a pharmaceutical composition. The naked iRNA may be in a suitable buffer solution. The buffer solution may comprise acetate, citrate, prolamine, carbonate, or phosphate, or any combination thereof. In one embodiment, the buffer solution is phosphate buffered saline (PBS). The pH and osmolarity of the buffer solution containing the iRNA can be adjusted such that it is suitable for administering to a subject. 
     Alternatively, an iRNA of the invention may be administered as a pharmaceutical composition, such as a dsRNA liposomal formulation. 
     Subjects that would benefit from a reduction or inhibition of PD-L1 gene expression are those having a disorder that would benefit from an increased immune response, e.g., an infectious disease, e.g., a viral disease, e.g., hepatitis; or cancer. 
     The iRNA and additional therapeutic agents may be administered at the same time or in the same combination, e.g., parenterally, or the additional therapeutic agent can be administered as part of a separate composition or at separate times or by another method known in the art or described herein. 
     In one embodiment, the method includes administering a composition featured herein such that expression of the target PD-L1 gene is decreased, such as for about 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 18, 24 hours, 28, 32, or about 36 hours. In one embodiment, expression of the target PD-L1 gene is decreased for an extended duration, e.g., at least about two, three, four days or more, e.g., about one week, two weeks, three weeks, or four weeks or longer, e.g., about 1 month, 2 months, or 3 months. 
     Preferably, the iRNAs useful for the methods and compositions featured herein specifically target RNAs (primary or processed) of the target PD-L1 gene. Compositions and methods for inhibiting the expression of these genes using iRNAs can be prepared and performed as described herein. 
     Administration of the iRNA according to the methods of the invention may result in a reduction of the severity, signs, symptoms, or markers of such diseases or disorders in a patient with, e.g., elevated PD-L1 or a PD-L1 responsive tumor. By “reduction” in this context is meant a statistically significant decrease in such level, e.g., the level of an indicator of the presence of a pathogen in a subject, e.g., HBsAg, HBeAg, or HB cccDNA in the serum of a subject infected with hepatitis B. The reduction can be, for example, at least about 20%, 25%, preferably at least 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, or to below the level of detection of the assay used. In certain embodiment, an increase in a marker, e.g., anti-HBs antibody is indicative of a reduction of the severity of the disease. Therefore, an increase can be a statistically significant increase in the level of antibody, e.g., to a detectable level in a subject. 
     Efficacy of treatment or prevention of disease can be assessed, for example by measuring disease progression, disease remission, symptom severity, reduction in pain, quality of life, dose of a medication required to sustain a treatment effect, level of a disease marker, or any other measurable parameter appropriate for a given disease being treated or targeted for prevention. It is well within the ability of one skilled in the art to monitor efficacy of treatment or prevention by measuring any one of such parameters, or any combination of parameters. For example, efficacy of treatment of a disorder that would benefit from an increased immune response, e.g., an infectious disease, e.g., a viral disease, e.g., hepatitis, or cancer. 
     Efficacy of treatment of an infectious disease can be demonstrated, for example, by a decrease in the presence of the infectious agent as demonstrated by an inability to culture the agent from a subject sample. Efficacy of treatment of an infectious disease can be demonstrated by a decrease in the presence of the infectious agent as demonstrated, for example, by a decrease in a protein, nucleic acid, or carbohydrate present in the infectious agent. Efficacy of treatment can be demonstrated, for example, by the presence of an immune response as demonstrated by the presence of antibodies or immune cells targeted against the infectious agent. Efficacy of treatment of an infectious disease can be demonstrated by a decrease in the presence of the infectious agent as demonstrated, for example, by a decrease in one or more signs or symptoms of the infection, e.g., fever, pain, nausea, vomiting, abnormal blood chemistry, weight loss. The specific signs or symptoms will depend on the specific pathogen. Efficacy of treatment of an infectious disease can be demonstrated by the development of antibodies or immune cells targeting the pathogen. 
     Efficacy of treatment of cancer can be demonstrated by stabilization or a decrease in tumor burden as demonstrated by a stabilization or decrease in tumor burden of the primary tumor, metastatic tumors, or the delay or prevention of tumor metastasis. Diagnostic and monitoring methods are provided herein, e.g., RECIST criteria. 
     Comparisons of the later readings with the initial readings provide a physician an indication of whether the treatment is effective. It is well within the ability of one skilled in the art to monitor efficacy of treatment or prevention by measuring any one of such parameters, or any combination of parameters. In connection with the administration of an iRNA targeting PD-L1 or pharmaceutical composition thereof, “effective against” a PD-L1 related disorder indicates that administration in a clinically appropriate manner results in a beneficial effect for at least a statistically significant fraction of patients, such as a improvement of symptoms, a cure, a reduction in disease, extension of life, improvement in quality of life, or other effect generally recognized as positive by medical doctors familiar with treating PD-L1-related disorders as provided, for example, in the diagnostic criteria for HBV provided herein. 
     A treatment or preventive effect is evident when there is a statistically significant improvement in one or more parameters of disease status, or by a failure to worsen or to develop symptoms where they would otherwise be anticipated. As an example, a favorable change of at least 10% in a measurable parameter of disease, and preferably at least 20%, 30%, 40%, 50% or more can be indicative of effective treatment. Efficacy for a given iRNA drug or formulation of that drug can also be judged using an experimental animal model for the given disease as known in the art. When using an experimental animal model, efficacy of treatment is evidenced when a statistically significant reduction in a marker or symptom is observed. 
     Alternatively, the efficacy can be measured by a reduction in the severity of disease as determined by one skilled in the art of diagnosis based on a clinically accepted disease severity grading scale. Any positive change resulting in e.g., lessening of severity of disease measured using the appropriate scale, represents adequate treatment using an iRNA or iRNA formulation as described herein. 
     Subjects can be administered a therapeutic amount of iRNA, such as about 0.01 mg/kg to about 200 mg/kg. 
     The iRNA can be administered by intravenous infusion over a period of time, on a regular basis. In certain embodiments, after an initial treatment regimen, the treatments can be administered on a less frequent basis. Administration of the iRNA can reduce PD-L1 levels, e.g., in a cell or tissue of the patient by at least about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, or below the level of detection of the assay method used. In certain embodiments, administration results in clinical stabilization or preferably clinically relevant reduction of at least one sign or symptom of a PD-L1 associated disorder. 
     In certain embodiments, a full dose of the iRNA, patients can be administered a smaller dose, such as a 5% infusion reaction, and monitored for adverse effects, such as an allergic reaction. In another example, the patient can be monitored for unwanted immunostimulatory effects, such as increased cytokine (e.g., TNF-alpha or INF-alpha) levels. 
     Alternatively, the iRNA can be administered subcutaneously, i.e., by subcutaneous injection. One or more injections may be used to deliver the desired daily dose of iRNA to a subject. The injections may be repeated over a period of time. The administration may be repeated on a regular basis. In certain embodiments, after an initial treatment regimen, the treatments can be administered on a less frequent basis. A repeat-dose regimen may include administration of a therapeutic amount of iRNA on a regular basis, such as every other day or to once a year. In certain embodiments, the iRNA is administered about once per month to about once per quarter (i.e., about once every three months). 
     IX. Diagnostic Criteria and Treatment for PD-L1 Related Diseases 
     Exemplary diagnostic and monitoring criteria for various PD-L1 related diseases are provided below. 
     A. Hepatitis B 
     Hepatitis is a general term meaning inflammation of the liver and can be caused by a variety of different viruses such as hepatitis A, B, C, D and E. Since the development of jaundice is a characteristic feature of liver disease, a correct diagnosis can only be made by testing patients&#39; sera for the presence of specific anti-viral antigens or antibodies. The severe pathological consequences of persistent HBV infections include the development of chronic hepatic insufficiency, cirrhosis, and hepatocellular carcinoma (HCC). In addition, HBV carriers can transmit the disease for many years. 
     HBV is a large virus and does not cross the placenta, however, pregnant women who are infected with HBV can transmit their disease to their infants at birth. If not vaccinated at birth, many of these infants develop lifelong HBV infections, and many develop liver failure or liver cancer later in life. Following acute HBV infection, the risk of developing chronic infection varies inversely with age. Chronic HBV infection occurs among about 90% of infants infected at birth, 25-50% of children infected at 1-5 years of age and about 1-5% of persons infected as older children and adults. Chronic HBV infection is also common in persons with immunodeficiency (Hepatitis B: World Health Organization. Department of Communicable Diseases Surveillance and Response, available at www.who.int/csr/disease/hepatitis/HepatitisB_whocdscsrlyo2002_2. pdf?ua=1, incorporated herein by reference). 
     During the incubation phase of the disease (6 to 24 weeks), patients may feel unwell with possible nausea, vomiting, diarrhea, anorexia, and headaches. Patients may then become jaundiced although low grade fever and loss of appetite may improve. Sometimes HBV infection produces neither jaundice nor obvious symptoms. The asymptomatic cases can be identified by detecting biochemical or virus-specific serologic alterations in their blood. Such asymptomatic individuals may become silent carriers of the virus and constitute a reservoir for further transmission to others. 
     Most adult patients recover completely from their HBV infection, but others, about 5 to 10%, will not clear the virus and will progress to become asymptomatic carriers or develop chronic hepatitis possibly resulting in cirrhosis or liver cancer. Rarely, some patients may develop fulminant hepatitis and die. Persistent or chronic HBV infection is among the most common persistent viral infections in humans. More than 350 million people in the world today are estimated to be persistently infected with HBV. A large fraction of these are in eastern Asia and sub-Saharan Africa, where the associated complications of chronic liver disease and liver cancer are the most important health problems. 
     The three standard blood tests for hepatitis B (HBs antigen, antiHBs antibody, and HBc antigen) can determine if a person is currently infected with HBV, has recovered, is a chronic carrier, or is susceptible to HBV infection. 
     
       
         
           
               
               
            
               
                   
               
               
                 Assay results 
                   
               
            
           
           
               
               
               
               
            
               
                 HBsAg 
                 anti-HBs 
                 anti-HBc 
                 Interpretation 
               
               
                   
               
               
                 + 
                 − 
                 − 
                 Early acute HBV infection. 
               
               
                 + 
                 +/− 
                 + 
                 Acute or chronic HBV infection. Differentiate with IgM-anti- 
               
               
                   
                   
                   
                 HBc. Determine level of infectivity with HBeAg or HBV DNA. 
               
               
                 − 
                 + 
                 + 
                 Indicates previous HBV infection and immunity to hepatitis B. 
               
               
                 − 
                 − 
                 + 
                 Possibilities include: past HBV infection; low-level HBV 
               
               
                   
                   
                   
                 carrier; time span between disappearance of HBsAg and 
               
               
                   
                   
                   
                 appearance of anti-HBs; or false-positive or nonspecific 
               
               
                   
                   
                   
                 reaction. Investigate with IgM anti-HBc, and/or challenge with 
               
               
                   
                   
                   
                 HBsAg vaccine. When present, anti-HBe helps validate the 
               
               
                   
                   
                   
                 anti-HBc reactivity. 
               
               
                 − 
                 − 
                 − 
                 Another infectious agent, toxic injury to the liver, disorder of 
               
               
                   
                   
                   
                 immunity, hereditary disease of the liver, or disease of the 
               
               
                   
                   
                   
                 biliary tract. 
               
               
                 − 
                 + 
                 − 
                 Vaccine-type response. 
               
               
                   
               
               
                 From: Hollinger F B, Liang T J. Hepatitis B Virus. In: Knipe D M et al., eds. Fields Virology, 4th ed., Philadelphia, Lippincott Williams &amp;Wilkins, 2001: 2971-3036. 
               
            
           
         
       
     
     Further serological tests can be performed to differentiate subjects with chronic or acute HBV, or who may be carriers. A number of vaccines against HBV are available and are presently far more effective, and cost-effective, than treatment. 
     Currently, there is no treatment available for acute hepatitis B. Symptomatic treatment of nausea, anorexia, vomiting, and other symptoms may be indicated. 
     Treatment of chronic hepatitis B is aimed at eliminating infectivity to prevent transmission and spread of HBV, at halting the progression of liver disease and improving the clinical and histologic picture, and at preventing HCC from developing, by losing markers of HBV replication in serum and liver like HBV DNA, HBeAg, and HBcAg. Normalization of ALT activity, resolution of hepatic inflammation and the improvement of a patient&#39;s symptoms usually accompany these virological changes. However, presently available treatments for HBV are rarely curative. Patients must be on treatment indefinitely to suppress the disease and prevent transmission. 
     There are two main classes of treatment: antivirals: aimed at suppressing or destroying HBV by interfering with viral replication; and immune modulators: aimed at helping the human immune system to mount a defence against the virus. Neither corticosteroids, which induce an enhanced expression of virus and viral antigens, and a suppression of T-lymphocyte function, nor adenine arabinoside, acyclovir, or dideoxyinosine, have been shown to be beneficial for the treatment of chronic hepatitis B. 
     Currently, chronic hepatitis B is treated with interferons to modulate immune response. The only approved ones are interferon-α-2a and interferon-α-2b. Interferons display a variety of properties that include antiviral, immunomodulatory, and antiproliferative effects. They enhance T-cell helper activity, cause maturation of B lymphocytes, inhibit T-cell suppressors, and enhance HLA type I expression. To be eligible for interferon therapy, patients should have infection documented for at least six months, elevated liver enzymes (AST and ALT), and an actively dividing virus in their blood (HBeAg and/or HBV DNA positive tests). Patients with acute infection, end stage cirrhosis or other major medical problems should not be treated. Interferon-α produces a long-term, sustained remission of the disease in 35% of those with chronic hepatitis B, with normalization of liver enzymes and loss of the three markers for an active infection (HBeAg, HBV DNA, and HBsAg). Complete elimination of the virus is achieved in some carefully selected patients. 
     Interferon therapy for patients with HBV-related cirrhosis decreases significantly the HCC rate, particularly in patients with a larger amount of serum HBV DNA. In patients with HBeAg-positive compensated cirrhosis, virological and biochemical remission following interferon therapy is associated with improved survival. In patients with chronic HBV infection, the clearance of HBeAg after treatment with interferon-α is associated with improved clinical outcomes. 
     Interferon-α (Intron A (interferon-α-2b), Schering Plough, and Roferon, (interferon-α-2a) Roche Labs) is the primary treatment for chronic hepatitis B. The standard duration of therapy is considered 16 weeks. Patients who exhibit a low level of viral replication at the end of the standard regimen benefit most from prolonged treatment. 
     Nucleotide and nucleoside analogs have long been used for the treatment of HBV. Compounds presently available and in development include lamivudine, adefovir, entecavir, telbivudine, tenofovir, emtricitabine, clevudine, ritonavir, dipivoxil, lobucavir, famvir, FTC, N-Acetyl-Cysteine (NAC), PC1323, theradigm-HBV, thymosin-alpha, and ganciclovir. Some are useful against other viral infections, e.g., HCV, HIV, whereas others are effective predominantly in the treatment of HBV. 
     Permanent loss of HBV DNA and HBeAg are considered the goals of antiviral treatment, as these result is associated with an improvement in necro-inflammatory damage, and reduced infectivity. 
     B. Hepatitis D 
     Hepatitis Delta virus (HDV) is a defective virus that is only infectious in the presence of active HBV infection. HDV infection occurs as either coinfection with HBV or superinfection of an HBV carrier. Coinfection usually resolves. Superinfection, however, causes frequently chronic HDV infection and chronic active hepatitis. Both types of infections may cause fulminant hepatitis. 
     Routes of transmission are similar to those of HBV. Preventing acute and chronic HBV infection of susceptible persons by vaccination will also prevent HDV infection. Certain HBV treatments are also effective in the treatment of HDV, e.g., interferon-alpha, with or without adefovir. However others, like lamivudine, an inhibitor of HBV-DNA replication, are not useful for the treatment of chronic hepatitis D. 
     C. Tuberculosis (TB) 
     Tuberculosis is a disease caused by  Mycobacterium tuberculosis . Tuberculosis is associated with symptoms including unexplained weight loss, loss of appetite, night sweates, fever, fatigue, coughing for longer than three weeks, hemoptysis (coughing up blood), and chest pain. There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the tuberculin skin test and TB blood tests which include QuantiFERON®-TB Gold In-Tube test (QFT-GIT) and T-SPOT®.TB test (T-Spot). However, the tests are not indicative of an active TB infection. Diagnosis of TB infection includes assessment of medical history, physical examination, chest radiography, and diagnostic microbiology culture assay including an analysis for drug resistance. Assessment of clinically relevant changes in signs or symptoms of TB is within the ability of those of skill in the art. 
     D. Cancer 
     Cancer refers to any of various malignant neoplasms characterized by the proliferation of anaplastic cells that tend to invade surrounding tissue and metastasize to new body sites and also refers to the pathological condition characterized by such malignant neoplastic growths. A cancer can be a tumor or hematological malignancy, and includes but is not limited to, all types of lymphomas/leukemias, carcinomas and sarcomas. In certain embodiments, cancer includes hepatic cancer. In certain embodiments, cancer includes hepatocellular carcinoma (HCC). 
     RECIST criteria are clinically accepted assessment criteria used to provide a standard approach to solid tumor measurement and provide definitions for objective assessment of change in tumor size for use in clinical trials. Such criteria can also be used to monitor response of an individual undergoing treatment for a solid tumor. The RECIST 1.1 criteria are discussed in detail in Eisenhauer et al., New response evaluation criteria in solid tumors: Revised RECIST guideline (version 1.1). Eur. J. Cancer. 45:228-247, 2009, which is incorporated herein by reference. Response criteria for target lesions include: 
     Complete Response (CR): Disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have a reduction in short axis to &lt;10 mm. 
     Partial Response (PR): At least a 30% decrease in the sum of diameters of target lesion, taking as a reference the baseline sum diameters. 
     Progressive Diseases (PD): At least a 20% increase in the sum of diameters of target lesions, taking as a reference the smallest sum on the study (this includes the baseline sum if that is the smallest on the study). In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm. (Note: the appearance of one or more new lesions is also considered progression.) 
     Stable Disease (SD): Neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD, taking as a reference the smallest sum diameters while on study. 
     RECIST 1.1 criteria also consider non-target lesions which are defined as lesions that may be measurable, but need not be measured, and should only be assessed qualitatively at the desired time points. Response criteria for non-target lesions include: 
     Complete Response (CR): Disappearance of all non-target lesions and normalization of tumor marker levels. All lymph nodes must be non-pathological in size (&lt;10 mm short axis). 
     Non-CR/Non-PD: Persistence of one or more non-target lesion(s) and/or maintenance of tumor marker level above the normal limits. 
     Progressive Disease (PD): Unequivocal progression of existing non-target lesions. The appearance of one or more new lesions is also considered progression. To achieve “unequivocal progression” on the basis of non-target disease, there must be an overall level of substantial worsening of non-target disease such that, even in the presence of SD or PR in target disease, the overall tumor burden has increased sufficiently to merit discontinuation of therapy. A modest “increase” in the size of one or more non-target lesions is usually not sufficient to qualify for unequivocal progression status. The designation of overall progression solely on the basis of change in non-target disease in the face of SD or PR in target disease will therefore be extremely rare. 
     Clinically acceptable criteria for response to treatment in acute leukemias are as follows: 
     Complete remission (CR): The patient must be free of all symptoms related to leukemia and have an absolute neutrophil count of ≥1.0×10 9 /L, platelet count ≥100×10 9 /L, and normal bone marrow with &lt;5% blasts and no Auer rods. 
     Complete remission with incomplete blood count recovery (Cri): As per CE, but with residual thrombocytopenia (platelet count &lt;100×10 9 /L) or residual neutropenia (absolute neutrophil count &lt;1.0×10 9 /L). 
     Partial remission (PR): A ≥50% decrease in bone marrow blasts to 5 to 25% abnormal cells in the marrow; or CR with ≤5% blasts if Auer rods are present. 
     Treatment failure: Treatment has failed to achieve CR, Cri, or PR. Recurrence. 
     Relapse after confirmed CR: Reappearance of leukemic blasts in peripheral blood or ≥5% blasts in the bone marrow not attributable to any other cause (e.g., bone marrow regeneration after consolidated therapy) or appearance of new dysplastic changes. 
     Uses of the compositions and methods of the invention include achieving at least stable disease in a subject with a solid tumor for sufficient time to meet the definition of stable disease by RECIST criteria. In certain embodiments, the use of the compositions and methods of the invention include achieving at least a partial response in a subject with a solid tumor for sufficient time to meet the definition of stable disease by RECIST criteria. 
     Uses of the compositions and methods of the invention include achieving at least a partial remission in a subject with an acute leukemia for sufficient time to meet the definition of stable disease by RECIST criteria. In certain embodiments, the use of the compositions and methods of the invention include achieving at least a complete remission with incomplete blood count recovery in a subject with an acute leukemia for sufficient time to meet the definition of stable disease by RECIST criteria. 
     This invention is further illustrated by the following examples which should not be construed as limiting. The entire contents of all references, patents and published patent applications cited throughout this application, as well as the Sequence Listing, are hereby incorporated herein by reference. 
     EXAMPLES 
     Example 1. iRNA Synthesis 
     Source of Reagents 
     Where the source of a reagent is not specifically given herein, such reagent can be obtained from any supplier of reagents for molecular biology at a quality/purity standard for application in molecular biology. 
     Transcripts 
     siRNA Design 
     A set of siRNAs targeting the human PD-L1/CD274 (human: NCBI refseqID NM_001267706; NCBI GeneID: 29126; SEQ ID NO:1), as well as toxicology-species PD-L1 orthologs (mouse: XM_006527249 (SEQ ID NO:3); rat, XM_006231248 (SEQ ID NO:5); and cynomolgus monkey: XM_005581779 (SEQ ID NO: 7)) were designed using custom R and Python scripts. The human PD-L1 REFSEQ mRNA has a length of 3349 bases. The rationale and method for the set of siRNA designs is as follows: the predicted efficacy for every potential 19 mer siRNA from position 109 through position 3349 (the coding region and 3′ UTR) was determined with a linear model derived the direct measure of mRNA knockdown from more than 20,000 distinct siRNA designs targeting a large number of vertebrate genes. Subsets of the PD-L1 siRNAs were designed with perfect or near-perfect matches between human and cynomolgus monkey. A further subset was designed with perfect or near-perfect matches to mouse and rat PD-L1 orthologs. A further subset was designed with perfect or near-perfect matches to human, cynomolgus monkey, mouse, and rat PD-L1 orthologs. For each strand of the siRNA, a custom Python script was used in a brute force search to measure the number and positions of mismatches between the siRNA and all potential alignments in the target species transcriptome. Extra weight was given to mismatches in the seed region, defined here as positions 2-9 of the antisense oligonucleotide, as well the cleavage site of the siRNA, defined here as positions 10-11 of the antisense oligonucleotide. The relative weight of the mismatches was 2.8; 1.2:1 for seed mismatches, cleavage site, and other positions up through antisense position 19. Mismatches in the first position were ignored. A specificity score was calculated for each strand by summing the value of each weighted mismatch. Preference was given to siRNAs whose antisense score in human and cynomolgus monkey was &gt;=3.0 and predicted efficacy was &gt;=70% knockdown of the PD-L1 transcript. 
     A detailed list of the unmodified PD-L1 sense and antisense strand sequences is shown in Table 3. A detailed list of the modified PD-L1 sense and antisense strand sequences is shown in Table 5. 
     siRNA Synthesis 
     PD-L1 siRNA sequences were synthesized at 1 μmol scale on a Mermade 192 synthesizer (BioAutomation) using the solid support mediated phosphoramidite chemistry. The solid support was controlled pore glass (500 A) loaded with custom GalNAc ligand or universal solid support (AM biochemical). Ancillary synthesis reagents, 2′-F and 2′-O-Methyl RNA and deoxy phosphoramidites were obtained from Thermo-Fisher® (Milwaukee, Wis.) and Hongene (China). 2′F 2′-O-Methyl, GNA (glycol nucleic acids), 5′phosphate and other modifications are introduced using the corresponding phosphoramidites. Synthesis of 3′ GalNAc conjugated single strands was performed on a GalNAc modified CPG support. Custom CPG universal solid support was used for the synthesis of antisense single strands. Coupling time for all phosphoramidites (100 mM in acetonitrile) is 5 min employing 5-Ethylthio-1H-tetrazole (ETT) as activator (0.6 M in acetonitrile). Phosphorothioate linkages were generated using a 50 mM solution of 3-((Dimethylamino-methylidene) amino)-3H-1,2,4-dithiazole-3-thione (DDTT, obtained from Chemgenes® (Wilmington, Mass., USA)) in anhydrous acetonitrile/pyridine (1:1 v/v). Oxidation time was 3 minutes. All sequences were synthesized with final removal of the DMT group (“DMT off”). 
     Upon completion of the solid phase synthesis, oligoribonucleotides were cleaved from the solid support and deprotected in sealed 96 deep well plates using 200 μL Aqueous Methylamine reagents at 60° C. for 20 minutes. For sequences containing 2′ ribo residues (2′-OH) that are protected with a tert-butyl dimethyl silyl (TBDMS) group, a second step deprotection is performed using TEA.3HF (triethylamine trihydro fluoride) reagent. To the methylamine deprotection solution, 200 uL of dimethyl sulfoxide (DMSO) and 300 ul TEA.3HF reagent were added and the solution was incubated for additional 20 min at 60° C. At the end of cleavage and deprotection step, the synthesis plate was allowed to come to room temperature and is precipitated by addition of 1 mL of acetontile: ethanol mixture (9:1). The plates are cooled at −80 C for 2 hrs, superanatant was decanted carefully with the aid of a multi channel pipette. The oligonucleotide pellet was re-suspended in 20 mM NaOAc buffer and is desalted using a 5 mL HiTrap® size exclusion column (GE Healthcare) on an AKTA® Purifier System equipped with an A905 autosampler and a Frac 950 fraction collector. Desalted samples are collected in 96-well plates. Samples from each sequence were analyzed by LC-MS to confirm the identity, UV (260 nm) for quantification and a selected set of samples by IEX chromatography to determine purity. 
     Annealing of PD-L1 single strands was performed on a Tecan® liquid handling robot. Equimolar mixture of sense and antisense single strands were combined and annealed in 96 well plates. After combining the complementary single strands, the 96-well plate was sealed tightly and heated in an oven at 100° C. for 10 minutes and allowed to come slowly to room temperature over a period 2-3 hours. The concentration of each duplex was normalized to 10 μM in 1×PBS. 
     Example 2—In Vitro Screening 
     Cell Culture and Plasmids/Transfections for Dual-Glo® Assay: 
     Cos 7 cells (ATCC®, Manassas, Va.) were grown to near confluence at 37° C. in an atmosphere of 5% CO 2  in DMEM (ATCC®) supplemented with 10% FBS, before being released from the plate by trypsinization. The complete human CD274 reference sequence (NM_001267706.1) was cloned into the dual-luciferase psiCHECK2™ vector using three constructs with inserts of approximately 750 bp, 1.4 kb, and 1.4 kb in length (SEQ ID NOs: 11-13). Dual-luciferase plasmids were co-transfected with siRNA into 15×10 3  cells using Lipofectamine™ 2000 (Invitrogen™, Carlsbad Calif. cat #11668-019). For each well of a 96 well plate, 0.2 ul of Lipofectamine™ were added to 10 ng of plasmid vector and siRNA in 14.8 ul of Opti-MEM® and allowed to complex at room temperature for 15 minutes. The mixture was then added to the cells resuspended in 80 ul of fresh complete media. Cells were incubated for 48 hours before luciferase was measured. Single dose experiments were performed at 10 nM and 0.1 nM final duplex concentration. 
     Dual-Glo® Luciferase Assay 
     48 hours after the siRNAs were transfected, Firefly (transfection control) and Renilla (fused to PD-L1 target sequence in 3′ UTR) luciferase were measured. First, media was removed from cells. Then Firefly luciferase activity was measured by adding 75 ul of Dual-Glo® Luciferase Reagent equal to the culture medium volume to each well and mixing. The mixture was incubated at room temperature for 30 minutes before luminescence (500 nm) was measured on a Spectramax® (Molecular Devices®) to detect the Firefly luciferase signal. Renilla luciferase activity was measured by adding 75 ul of room temperature of Dual-Glo® Stop &amp; Glo® Reagent to each well and the plates were incubated for 10-15 minutes before luminescence was again measured to determine the Renilla luciferase signal. The Dual-Glo® Stop &amp; Glo® Reagent quenches the firefly luciferase signal and sustained luminescence for the Renilla luciferase reaction. siRNA activity was determined by normalizing the Renilla (PD-L1) signal to the Firefly (control) signal within each well. The magnitude of siRNA activity was then assessed relative to cells that were transfected with the same vector but were not treated with siRNA or were treated with a non-targeting siRNA. All transfections were done in triplicate. 
     Cell Culture and Transfections for qPCR: 
     RKO human colon carcinoma cells (ATCC®, Manassas, Va.) were grown to near confluence at 37° C. in an atmosphere of 5% CO 2  in EMEM (ATCC®) supplemented with 10% FBS, before being released from the plate by trypsinization. 
     Cells were transfected by adding 4.9 μl of Opti-MEM plus 0.1 μl of Lipofectamine™ RNAiMax per well (Invitrogen™, Carlsbad Calif. cat #13778-150) to 5 μl of siRNA duplexes per well into a 384-well plate and incubated at room temperature for 15 minutes. 40 μl of DMEM containing ˜5×10 3  cells were then added to the siRNA mixture. Cells were incubated for 24 hours prior to RNA purification. Single dose experiments were performed at 10 nM and 0.1 nM final duplex concentration. 
     Total RNA Isolation Using DYNABEADS® mRNA Isolation Kit: 
     RNA was isolated using an automated protocol on a BioTek-EL406 platform using DYNABEADs® (Invitrogen™, cat #61012). Briefly, 50 μl of Lysis/Binding Buffer and 25 μl of lysis buffer containing 3 μl of magnetic beads were added to the plate with cells. Plates were incubated on an electromagnetic shaker for 10 minutes at room temperature and then magnetic beads were captured and the supernatant was removed. Bead-bound RNA was then washed 2 times with 150 μl Wash Buffer A and once with Wash Buffer B. Beads were then washed with 150 μl Elution Buffer, re-captured and supernatant removed. 
     cDNA Synthesis Using ABI™ High Capacity cDNA Reverse Transcription Kit (Applied Biosystems®, Foster City, Calif., Cat #4368813): 
     Ten μl of a master mix containing 1 μl 10× Buffer, 0.4 μl 25× dNTPs, 1 μl 10× Random primers, 0.5 μl Reverse Transcriptase, 0.5 μl RNase inhibitor and 6.6 μl of H 2 O per reaction was added to RNA isolated above. Plates were sealed, mixed, and incubated on an electromagnetic shaker for 10 minutes at room temperature, followed by 2 h 37° C. Plates were then incubated at 81° C. for 5 min. 
     Real Time PCR: 
     Two μl of cDNA were added to a master mix containing 0.5 μl of GAPDH TaqMan® Probe (Hs99999905), 0.5 μl CD274 probe (Hs01125301_ml, CD274) and 50 Lightcycler® 480 probe master mix (Roche Cat #04887301001) per well in a 384 well plates (Roche cat #04887301001). Real time PCR was done in a LightCycler®480 Real Time PCR system (Roche) using the ΔΔCt(RQ) assay. Each duplex was tested in four independent transfections. 
     To calculate relative fold change, real time data were analyzed using the ΔΔCt method and normalized to assays performed with cells transfected with 10 nM AD-1955, or mock transfected cells. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Abbreviations of nucleotide monomers used in nucleic acid sequence 
               
               
                 representation. It will be understood that these monomers, when present 
               
               
                 in an oligonucleotide, are mutually linked by 5′-3′-phosphodiester bonds. 
               
            
           
           
               
               
            
               
                 Abbreviation 
                 Nucleotide(s) 
               
               
                   
               
               
                 A 
                 Adenosine-3′-phosphate 
               
               
                 Af 
                 2′-fluoroadenosine-3′-phosphate 
               
               
                 Afs 
                 2′-fluoroadenosine-3′-phosphorothioate 
               
               
                 As 
                 adenosine-3′-phosphorothioate 
               
               
                 C 
                 cytidine-3′-phosphate 
               
               
                 Cf 
                 2′-fluorocytidine-3′-phosphate 
               
               
                 Cfs 
                 2′-fluorocytidine-3′-phosphorothioate 
               
               
                 Cs 
                 cytidine-3′-phosphorothioate 
               
               
                 G 
                 guanosine-3′-phosphate 
               
               
                 Gf 
                 2′-fluoroguanosine-3′-phosphate 
               
               
                 Gfs 
                 2′-fluoroguanosine-3′-phosphorothioate 
               
               
                 Gs 
                 guanosine-3′-phosphorothioate 
               
               
                 T 
                 5′-methyluridine-3′-phosphate 
               
               
                 Tf 
                 2′-fluoro-5-methyluridine-3′-phosphate 
               
               
                 Tfs 
                 2′-fluoro-5-methyluridine-3′-phosphorothioate 
               
               
                 Ts 
                 5-methyluridine-3′-phosphorothioate 
               
               
                 U 
                 Uridine-3′-phosphate 
               
               
                 Uf 
                 2′-fluorouridine-3′-phosphate 
               
               
                 Ufs 
                 2′-fluorouridine-3′-phosphorothioate 
               
               
                 Us 
                 uridine-3′-phosphorothioate 
               
               
                 N 
                 any nucleotide (G, A, C, T or U) 
               
               
                 a 
                 2′-O-methyladenosine-3′-phosphate 
               
               
                 as 
                 2′-O-methyladenosine-3′-phosphorothioate 
               
               
                 c 
                 2′-O-methylcytidine-3′-phosphate 
               
               
                 cs 
                 2′-O-methylcytidine-3′-phosphorothioate 
               
               
                 g 
                 2′-O-methylguanosine-3′-phosphate 
               
               
                 gs 
                 2′-O-methylguanosine-3′-phosphorothioate 
               
               
                 t 
                 2′-O-methyl-5-methyluridine-3′-phosphate 
               
               
                 ts 
                 2′-O-methyl-5-methyluridine-3′-phosphorothioate 
               
               
                 u 
                 2′-O-methyluridine-3′-phosphate 
               
               
                 us 
                 2′-O-methyluridine-3′-phosphorothioate 
               
               
                 s 
                 phosphorothioate linkage 
               
               
                 L96 
                 N-[tris(GalNAc-alkyl)-amidodecanoyl)]-4-hydroxyprolinol Hyp-(GalNAc-alkyl)3 
               
               
                 dT 
                 2-deoxythymidine-3′-phosphate 
               
               
                 dC 
                 2′-deoxycytidine-3′-phosphate 
               
               
                 Y44 
                 inverted abasic DNA (2-hydroxymethyl-tetrahydrofurane-5-phosphate) 
               
               
                 (Tgn) 
                 Thymidine-glycol nucleic acid (GNA) S-Isomer 
               
               
                 P 
                 Phosphate 
               
               
                 VP 
                 Vinyl-phosphate 
               
               
                 (Aam) 
                 2′-O-(N-methylacetamide)adenosine-3&#39;-phosphate 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Unmodified Sense and Antisense Strand Sequences of PD-L1 dsRNAs 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Sense 
                   
                 Position 
                   
                 Antisense 
                   
                 Position 
                   
               
               
                 Duplex 
                 Oligo 
                   
                 in SEQ 
                 SEQ 
                 Oligo 
                   
                 in SEQ 
                 SEQ 
               
               
                 Name 
                 Name 
                 Sense Sequence 
                 ID: 1 
                 ID 
                 Name 
                 Antisense Sequence 
                 ID: 1 
                 ID 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 AD-67630 
                 A-135540 
                 GAAGCUUUUCAAUGUGACCAA 
                 332-351 
                 18 
                 A-135541 
                 UUGGUCACAUUGAAAAGCUUCUC 
                 330-351 
                 19 
               
               
                   
               
               
                 AD-67639 
                 A-135560 
                 GAAGCUUUUCAAUGUGACCAA 
                 332-351 
                 20 
                 A-135561 
                 UUGGUCACAUUGAAAAGCUUCUC 
                 330-351 
                 21 
               
               
                   
               
               
                 AD-67649 
                 A-135560 
                 GAAGCUUUUCAAUGUGACCAA 
                 332-351 
                 22 
                 A-135576 
                 UUGGUCACAUUGAAAAGCUUCUC 
                 330-351 
                 23 
               
               
                   
               
               
                 AD-67634 
                 A-135550 
                 AGCUUUUCAAUGUGACCAGCA 
                 334-353 
                 24 
                 A-135551 
                 UGCUGGUCACAUUGAAAAGCUUC 
                 332-353 
                 25 
               
               
                   
               
               
                 AD-67644 
                 A-135570 
                 AGCUUUUCAAUGUGACCAGCA 
                 334-353 
                 26 
                 A-135571 
                 UGCUGGUCACAUUGAAAAGCUUC 
                 332-353 
                 27 
               
               
                   
               
               
                 AD-67654 
                 A-135570 
                 AGCUUUUCAAUGUGACCAGCA 
                 334-353 
                 28 
                 A-135581 
                 UGCUGGUCACAUUGAAAAGCUUC 
                 332-353 
                 29 
               
               
                   
               
               
                 AD-67627 
                 A-135534 
                 GCUUUUCAAUGUGACCAGCAA 
                 335-354 
                 30 
                 A-135535 
                 UUGCUGGUCACAUUGAAAAGCUU 
                 333-354 
                 31 
               
               
                   
               
               
                 AD-67636 
                 A-135554 
                 GCUUUUCAAUGUGACCAGCAA 
                 335-354 
                 32 
                 A-135555 
                 UUGCUGGUCACAUUGAAAAGCUU 
                 333-354 
                 33 
               
               
                   
               
               
                 AD-67646 
                 A-135554 
                 GCUUUUCAAUGUGACCAGCAA 
                 335-354 
                 34 
                 A-135573 
                 UUGCUGGUCACAUUGAAAAGCUU 
                 333-354 
                 35 
               
               
                   
               
               
                 AD-67658 
                 A-135590 
                 CACACUGAGAAUCAACACAAA 
                 353-372 
                 36 
                 A-135591 
                 UUUGUGUUGAUUCUCAGUGUGCU 
                 351-372 
                 37 
               
               
                   
               
               
                 AD-67657 
                 A-135586 
                 CCAAAUGAAAGGACUCACUUA 
                 471-490 
                 38 
                 A-135587 
                 UAAGUGAGUCCUUUCAUUUGGAG 
                 469-490 
                 39 
               
               
                   
               
               
                 AD-67632 
                 A-135546 
                 UACACAUUUGGAGGAGACGUA 
                 620-639 
                 40 
                 A-135547 
                 UACGUCUCCUCCAAAUGUGUAUC 
                 618-639 
                 41 
               
               
                   
               
               
                 AD-67642 
                 A-135566 
                 UACACAUUUGGAGGAGACGUA 
                 620-639 
                 42 
                 A-135567 
                 UACGUCUCCUCCAAAUGUGUAUC 
                 618-639 
                 43 
               
               
                   
               
               
                 AD-67652 
                 A-135566 
                 UACACAUUUGGAGGAGACGUA 
                 620-639 
                 44 
                 A-135579 
                 UACGUCUCCUCCAAAUGUGUAUC 
                 618-639 
                 45 
               
               
                   
               
               
                 AD-67629 
                 A-135538 
                 ACACAUUUGGAGGAGACGUAA 
                 621-640 
                 46 
                 A-135539 
                 UUACGUCUCCUCCAAAUGUGUAU 
                 619-640 
                 47 
               
               
                   
               
               
                 AD-67638 
                 A-135558 
                 ACACAUUUGGAGGAGACGUAA 
                 621-640 
                 48 
                 A-135559 
                 UUACGUCUCCUCCAAAUGUGUAU 
                 619-640 
                 49 
               
               
                   
               
               
                 AD-67648 
                 A-135558 
                 ACACAUUUGGAGGAGACGUAA 
                 621-640 
                 50 
                 A-135575 
                 UUACGUCUCCUCCAAAUGUGUAU 
                 619-640 
                 51 
               
               
                   
               
               
                 AD-67631 
                 A-135544 
                 CACAUUUGGAGGAGACGUAAU 
                 622-641 
                 52 
                 A-135545 
                 AUUACGUCUCCUCCAAAUGUGUA 
                 620-641 
                 53 
               
               
                   
               
               
                 AD-67641 
                 A-135564 
                 CACAUUUGGAGGAGACGUAAU 
                 622-641 
                 54 
                 A-135565 
                 AUUACGUCUCCUCCAAAUGUGUA 
                 620-641 
                 55 
               
               
                   
               
               
                 AD-67651 
                 A-135564 
                 CACAUUUGGAGGAGACGUAAU 
                 622-641 
                 56 
                 A-135578 
                 AUUACGUCUCCUCCAAAUGUGUA 
                 620-641 
                 57 
               
               
                   
               
               
                 AD-67675 
                 A-135630 
                 GAGACCUUGAUACUUUCAAAU 
                 848-867 
                 58 
                 A-135631 
                 AUUUGAAAGUAUCAAGGUCUCCC 
                 846-867 
                 59 
               
               
                   
               
               
                 AD-67665 
                 A-135608 
                 UAAUUUGAGGGUCAGUUCCUA 
                 978-997 
                 60 
                 A-135609 
                 UAGGAACUGACCCUCAAAUUAGG 
                 976-997 
                 61 
               
               
                   
               
               
                 AD-67633 
                 A-135548 
                 UUCCUAUUUAUUUUGAGUCUA 
                 1095-1114 
                 62 
                 A-135549 
                 UAGACUCAAAAUAAAUAGGAAAA 
                 1093-1114 
                 63 
               
               
                   
               
               
                 AD-67643 
                 A-135568 
                 UUCCUAUUUAUUUUGAGUCUA 
                 1095-1114 
                 64 
                 A-135569 
                 UAGACUCAAAAUAAAUAGGAAAA 
                 1093-1114 
                 65 
               
               
                   
               
               
                 AD-67653 
                 A-135568 
                 UUCCUAUUUAUUUUGAGUCUA 
                 1095-1114 
                 66 
                 A-135580 
                 UAGACUCAAAAUAAAUAGGAAAA 
                 1093-1114 
                 67 
               
               
                   
               
               
                 AD-67640 
                 A-135562 
                 UCCUAUUUAUUUUGAGUCUGU 
                 1096-1115 
                 68 
                 A-135563 
                 ACAGACUCAAAAUAAAUAGGAAA 
                 1094-1115 
                 69 
               
               
                   
               
               
                 AD-67650 
                 A-135562 
                 UCCUAUUUAUUUUGAGUCUGU 
                 1096-1115 
                 70 
                 A-135577 
                 ACAGACUCAAAAUAAAUAGGAAA 
                 1094-1115 
                 71 
               
               
                   
               
               
                 AD-67663 
                 A-135604 
                 UUGAAGAUAUAUUGUAGUAGA 
                 1159-1178 
                 72 
                 A-135605 
                 UCUACUACAAUAUAUCUUCAAAA 
                 1157-1178 
                 73 
               
               
                   
               
               
                 AD-67676 
                 A-135632 
                 AUUGUAGUAGAUGUUACAAUU 
                 1169-1188 
                 74 
                 A-135633 
                 AAUUGUAACAUCUACUACAAUAU 
                 1167-1188 
                 75 
               
               
                   
               
               
                 AD-67666 
                 A-135610 
                 GUAUUUGUAAGGUGCUUGGUA 
                 1247-1266 
                 76 
                 A-135611 
                 UACCAAGCACCUUACAAAUACUC 
                 1245-1266 
                 77 
               
               
                   
               
               
                 AD-67661 
                 A-135596 
                 AAGCAUAAAGAUCAAACCGUU 
                 1295-1314 
                 78 
                 A-135597 
                 AACGGUUUGAUCUUUAUGCUUCC 
                 1293-1314 
                 79 
               
               
                   
               
               
                 AD-67669 
                 A-135618 
                 CCUUUAUUUAACCCAUUAAUA 
                 1333-1352 
                 80 
                 A-135619 
                 UAUUAAUGGGUUAAAUAAAGGUG 
                 1331-1352 
                 81 
               
               
                   
               
               
                 AD-67667 
                 A-135612 
                 AGGAAGCAAACAGAUUAAGUA 
                 1520-1539 
                 82 
                 A-135613 
                 UACUUAAUCUGUUUGCUUCCUCA 
                 1518-1539 
                 83 
               
               
                   
               
               
                 AD-67674 
                 A-135628 
                 CAGGCAUUGAAUCUACAGAUA 
                 1684-1703 
                 84 
                 A-135629 
                 UAUCUGUAGAUUCAAUGCCUGGC 
                 1682-1703 
                 85 
               
               
                   
               
               
                 AD-67655 
                 A-135582 
                 UGAUUCAAAAUUCAAAAGAUA 
                 2105-2124 
                 86 
                 A-135583 
                 UAUCUUUUGAAUUUUGAAUCAUG 
                 2103-2124 
                 87 
               
               
                   
               
               
                 AD-67672 
                 A-135624 
                 UCUAAAGAUAGUCUACAUUUA 
                 2222-2241 
                 88 
                 A-135625 
                 UAAAUGUAGACUAUCUUUAGAAG 
                 2220-2241 
                 89 
               
               
                   
               
               
                 AD-67659 
                 A-135592 
                 GGAAAUGUAUGUUAAAAGCAA 
                 2242-2261 
                 90 
                 A-135593 
                 UUGCUUUUAACAUACAUUUCCAA 
                 2240-2261 
                 91 
               
               
                   
               
               
                 AD-67673 
                 A-135626 
                 UGUUUUCUGCUUUCUGUCAAA 
                 2650-2669 
                 92 
                 A-135627 
                 UUUGACAGAAAGCAGAAAACAAA 
                 2648-2669 
                 93 
               
               
                   
               
               
                 AD-67664 
                 A-135606 
                 UUUCUGUCAAGUAUAAACUUA 
                 2660-2679 
                 94 
                 A-135607 
                 UAAGUUUAUACUUGACAGAAAGC 
                 2658-2679 
                 95 
               
               
                   
               
               
                 AD-67662 
                 A-135598 
                 UUCUGUCAAGUAUAAACUUCA 
                 2661-2680 
                 96 
                 A-135599 
                 UGAAGUUUAUACUUGACAGAAAG 
                 2659-2680 
                 97 
               
               
                   
               
               
                 AD-67671 
                 A-135622 
                 GUACUUGCAAAAUCACAUUUU 
                 2692-2711 
                 98 
                 A-135623 
                 AAAAUGUGAUUUUGCAAGUACAG 
                 2690-2711 
                 99 
               
               
                   
               
               
                 AD-67670 
                 A-135620 
                 UUCUUUGUGUGAAUUACAGGA 
                 3033-3052 
                 100 
                 A-135621 
                 UCCUGUAAUUCACACAAAGAACA 
                 3031-3052 
                 101 
               
               
                   
               
               
                 AD-67668 
                 A-135616 
                 UGUGGUGUUGGAUUUGUAAGA 
                 3117-3136 
                 102 
                 A-135617 
                 UCUUACAAAUCCAACACCACAAG 
                 3115-3136 
                 103 
               
               
                   
               
               
                 AD-67660 
                 A-135594 
                 UCCCUUUUGUCUCAUGUUUCA 
                 3145-3164 
                 104 
                 A-135595 
                 UGAAACAUGAGACAAAAGGGAUA 
                 3143-3164 
                 105 
               
               
                   
               
               
                 AD-67656 
                 A-135584 
                 CUGCAUUUGAUUGUCACUUUU 
                 3200-3219 
                 106 
                 A-135585 
                 AAAAGUGACAAUCAAAUGCAGAA 
                 3198-3219 
                 107 
               
               
                   
               
               
                 AD-67628 
                 A-135536 
                 UACCUGCAUUAAUUUAAUAAA 
                 3223-3242 
                 108 
                 A-135537 
                 UUUAUUAAAUUAAUGCAGGUACA 
                 3221-3242 
                 109 
               
               
                   
               
               
                 AD-67637 
                 A-135556 
                 UACCUGCAUUAAUUUAAUAAA 
                 3223-3242 
                 110 
                 A-135557 
                 UUUAUUAAAUUAAUGCAGGUACA 
                 3221-3242 
                 111 
               
               
                   
               
               
                 AD-67647 
                 A-135556 
                 UACCUGCAUUAAUUUAAUAAA 
                 3223-3242 
                 112 
                 A-135574 
                 UUUAUUAAAUUAAUGCAGGUACA 
                 3221-3242 
                 113 
               
               
                   
               
               
                 AD-67626 
                 A-135532 
                 ACCUGCAUUAAUUUAAUAAAA 
                 3224-3243 
                 114 
                 A-135533 
                 UUUUAUUAAAUUAAUGCAGGUAC 
                 3222-3243 
                 115 
               
               
                   
               
               
                 AD-67635 
                 A-135552 
                 ACCUGCAUUAAUUUAAUAAAA 
                 3224-3243 
                 116 
                 A-135553 
                 UUUUAUUAAAUUAAUGCAGGUAC 
                 3222-3243 
                 117 
               
               
                   
               
               
                 AD-67645 
                 A-135552 
                 ACCUGCAUUAAUUUAAUAAAA 
                 3224-3243 
                 118 
                 A-135572 
                 UUUUAUUAAAUUAAUGCAGGUAC 
                 3222-3243 
                 119 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 CD274 Dual-Glo ® Luciferase and qPCR Data 
               
               
                 Data are expressed as percent message remaining relative to non-targeting control. 
               
            
           
           
               
               
               
               
            
               
                   
                 Luc Assay Data in Cos7 cells 
                 qPCR Data in RKO cells 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 10 nM 
                 10 nM 
                 0.1 nM 
                 0.1 nM 
                 10 nM 
                 10 nM 
                 0.1 nM 
                 0.1 nM 
                 Trans 
               
               
                 DuplexID 
                 AVG 
                 STDEV 
                 AVG 
                 STDEV 
                 AVG 
                 STDEV 
                 AVG 
                 STDEV 
                 start 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 AD-67630 
                 7.6 
                 0.4 
                 17.8 
                 1.2 
                 53.4 
                 3.5 
                 63.0 
                 15.2 
                 330 
               
               
                 AD-67639 
                 16.0 
                 2.5 
                 62.6 
                 2.8 
                 44.4 
                 2.8 
                 71.7 
                 5.5 
                 330 
               
               
                 AD-67649 
                 12.5 
                 1.2 
                 32.0 
                 10.0 
                 70.7 
                 6.9 
                 65.4 
                 11.6 
                 330 
               
               
                 AD-67634 
                 19.7 
                 1.6 
                 25.1 
                 1.0 
                 73.7 
                 13.6 
                 78.8 
                 5.8 
                 332 
               
               
                 AD-67644 
                 67.7 
                 5.5 
                 107.1 
                 3.9 
                 79.4 
                 5.1 
                 85.0 
                 4.2 
                 332 
               
               
                 AD-67654 
                 28.1 
                 1.8 
                 65.9 
                 5.2 
                 79.7 
                 4.0 
                 77.6 
                 9.8 
                 332 
               
               
                 AD-67627 
                 12.7 
                 2.3 
                 27.1 
                 0.9 
                 52.3 
                 3.4 
                 67.5 
                 1.9 
                 333 
               
               
                 AD-67636 
                 33.1 
                 6.0 
                 82.6 
                 5.0 
                 56.0 
                 3.9 
                 67.2 
                 23.7 
                 333 
               
               
                 AD-67646 
                 21.4 
                 1.0 
                 70.3 
                 8.4 
                 62.1 
                 5.7 
                 85.7 
                 4.9 
                 333 
               
               
                 AD-67658 
                 11.7 
                 0.1 
                 16.6 
                 0.8 
                 35.3 
                 5.4 
                 58.4 
                 3.2 
                 351 
               
               
                 AD-67657 
                 18.7 
                 3.2 
                 55.0 
                 3.0 
                 53.7 
                 8.4 
                 61.7 
                 15.7 
                 469 
               
               
                 AD-67632 
                 6.0 
                 0.3 
                 10.1 
                 0.8 
                 25.9 
                 4.9 
                 29.1 
                 15.5 
                 618 
               
               
                 AD-67642 
                 33.7 
                 3.6 
                 79.1 
                 0.7 
                 52.4 
                 4.9 
                 85.3 
                 0.6 
                 618 
               
               
                 AD-67652 
                 25.9 
                 5.9 
                 49.3 
                 0.9 
                 30.6 
                 1.7 
                 75.3 
                 4.0 
                 618 
               
               
                 AD-67629 
                 10.4 
                 0.6 
                 24.9 
                 1.9 
                 23.1 
                 1.9 
                 47.6 
                 4.8 
                 619 
               
               
                 AD-67638 
                 15.9 
                 1.2 
                 79.5 
                 5.1 
                 28.6 
                 2.9 
                 68.3 
                 6.7 
                 619 
               
               
                 AD-67648 
                 13.6 
                 1.2 
                 35.4 
                 5.3 
                 18.9 
                 4.3 
                 62.6 
                 7.0 
                 619 
               
               
                 AD-67631 
                 6.8 
                 1.0 
                 11.4 
                 0.8 
                 18.5 
                 2.8 
                 42.9 
                 1.2 
                 620 
               
               
                 AD-67641 
                 19.2 
                 3.2 
                 61.2 
                 9.4 
                 67.3 
                 8.7 
                 62.3 
                 11.4 
                 620 
               
               
                 AD-67651 
                 15.2 
                 0.9 
                 48.5 
                 1.1 
                 45.3 
                 5.9 
                 81.8 
                 7.6 
                 620 
               
               
                 AD-67675 
                 18.5 
                 1.1 
                 30.7 
                 4.2 
                 44.4 
                 4.8 
                 58.6 
                 8.6 
                 846 
               
               
                 AD-67665 
                 29.9 
                 1.1 
                 34.3 
                 2.8 
                 36.4 
                 2.0 
                 54.0 
                 4.4 
                 976 
               
               
                 AD-67633 
                 7.4 
                 0.8 
                 23.2 
                 1.0 
                 42.5 
                 4.9 
                 55.3 
                 26.1 
                 1093 
               
               
                 AD-67643 
                 9.2 
                 0.5 
                 57.4 
                 4.1 
                 32.7 
                 1.9 
                 71.5 
                 5.5 
                 1093 
               
               
                 AD-67653 
                 7.7 
                 0.1 
                 16.2 
                 1.2 
                 22.0 
                 1.8 
                 59.5 
                 4.8 
                 1093 
               
               
                 AD-67640 
                 6.7 
                 0.5 
                 31.8 
                 2.2 
                 18.4 
                 4.4 
                 45.1 
                 14.4 
                 1094 
               
               
                 AD-67650 
                 7.3 
                 0.7 
                 17.3 
                 2.3 
                 22.0 
                 1.7 
                 45.6 
                 3.2 
                 1094 
               
               
                 AD-67663 
                 13.2 
                 2.2 
                 33.8 
                 3.3 
                 35.7 
                 2.6 
                 46.5 
                 2.7 
                 1157 
               
               
                 AD-67676 
                 10.4 
                 1.2 
                 27.7 
                 3.1 
                 34.7 
                 4.3 
                 51.8 
                 4.4 
                 1167 
               
               
                 AD-67666 
                 9.3 
                 0.6 
                 14.7 
                 1.8 
                 47.5 
                 4.7 
                 63.4 
                 6.5 
                 1245 
               
               
                 AD-67661 
                 9.9 
                 0.6 
                 21.1 
                 1.1 
                 37.1 
                 2.0 
                 48.9 
                 3.1 
                 1293 
               
               
                 AD-67669 
                 25.4 
                 4.2 
                 51.9 
                 5.8 
                 52.0 
                 3.3 
                 73.3 
                 12.0 
                 1331 
               
               
                 AD-67667 
                 15.8 
                 4.0 
                 31.4 
                 1.0 
                 35.8 
                 0.3 
                 51.0 
                 3.7 
                 1518 
               
               
                 AD-67674 
                 13.8 
                 2.7 
                 21.3 
                 3.9 
                 43.1 
                 10.8 
                 61.2 
                 15.1 
                 1682 
               
               
                 AD-67655 
                 5.8 
                 1.5 
                 20.5 
                 3.2 
                 23.2 
                 3.4 
                 40.2 
                 3.7 
                 2103 
               
               
                 AD-67672 
                 5.7 
                 0.3 
                 13.5 
                 0.5 
                 36.1 
                 9.0 
                 52.5 
                 2.6 
                 2220 
               
               
                 AD-67659 
                 12.0 
                 1.8 
                 24.3 
                 4.3 
                 32.8 
                 2.4 
                 54.0 
                 5.5 
                 2240 
               
               
                 AD-67673 
                 8.1 
                 0.5 
                 44.0 
                 5.0 
                 33.2 
                 1.4 
                 58.8 
                 8.6 
                 2648 
               
               
                 AD-67664 
                 10.1 
                 0.4 
                 20.1 
                 4.9 
                 37.3 
                 2.9 
                 48.2 
                 3.1 
                 2658 
               
               
                 AD-67662 
                 14.6 
                 0.9 
                 25.9 
                 0.6 
                 28.6 
                 1.8 
                 40.3 
                 3.0 
                 2659 
               
               
                 AD-67671 
                 5.8 
                 1.0 
                 32.2 
                 7.4 
                 49.1 
                 2.0 
                 65.0 
                 3.5 
                 2690 
               
               
                 AD-67670 
                 9.6 
                 0.6 
                 28.7 
                 3.5 
                 41.0 
                 2.0 
                 63.6 
                 3.5 
                 3031 
               
               
                 AD-67668 
                 15.7 
                 3.2 
                 30.7 
                 6.3 
                 42.4 
                 7.2 
                 62.8 
                 2.2 
                 3115 
               
               
                 AD-67660 
                 4.9 
                 0.6 
                 17.1 
                 2.7 
                 29.2 
                 2.0 
                 53.5 
                 1.7 
                 3143 
               
               
                 AD-67656 
                 6.1 
                 1.0 
                 6.6 
                 0.7 
                 27.9 
                 6.6 
                 36.0 
                 7.0 
                 3198 
               
               
                 AD-67628 
                 11.6 
                 0.3 
                 26.8 
                 3.7 
                 38.8 
                 4.7 
                 53.1 
                 8.4 
                 3221 
               
               
                 AD-67637 
                 8.8 
                 0.6 
                 24.6 
                 4.2 
                 26.9 
                 0.7 
                 45.5 
                 7.8 
                 3221 
               
               
                 AD-67647 
                 9.1 
                 0.6 
                 23.7 
                 4.1 
                 25.2 
                 1.3 
                 47.3 
                 2.2 
                 3221 
               
               
                 AD-67626 
                 7.3 
                 0.6 
                 7.7 
                 0.4 
                 29.1 
                 8.9 
                 26.5 
                 9.4 
                 3222 
               
               
                 AD-67635 
                 9.3 
                 1.0 
                 28.2 
                 4.4 
                 26.3 
                 3.0 
                 49.7 
                 4.8 
                 3222 
               
               
                 AD-67645 
                 9.2 
                 1.0 
                 44.7 
                 7.2 
                 29.0 
                 1.5 
                 57.8 
                 5.0 
                 3222 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 PD-L1 Modified Sequences 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                 Trans 
               
               
                   
                   
                   
                   
                 Antisense 
                   
                   
                 start 
               
               
                 Duplex 
                 Sense 
                   
                 SEQ 
                 Oligo 
                 Antisense 
                 SEQ 
                 in SEQ 
               
               
                 Name 
                 OligoName 
                 Oligo Sequence 
                 ID 
                 Name 
                 Oligo Sequence 
                 ID 
                 ID: 1 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 AD-67630 
                 A-135540 
                 Y44GAAGCUUUUCAAUGUGACCAa 
                 120 
                 A-135541 
                 UUGGUCACAUUGAAAAGCUUCUc 
                 121 
                 330 
               
               
                   
               
               
                 AD-67639 
                 A-135560 
                 gsasagcuUfuUfCfAfaugugaccaaL96 
                 122 
                 A-135561 
                 usUfsgguCfaCfAfuugaAfaA 
                 123 
                 330 
               
               
                   
                   
                   
                   
                   
                 fgcuucsusc 
                   
                   
               
               
                   
               
               
                 AD-67649 
                 A-135560 
                 gsasagcuUfuUfCfAfaugugaccaaL96 
                 124 
                 A-135576 
                 UfsUfsgguCfaCfAfuugaAfa 
                 125 
                 330 
               
               
                   
                   
                   
                   
                   
                 Afgcuucsusc 
                   
                   
               
               
                   
               
               
                 AD-67634 
                 A-135550 
                 Y44AGCUUUUCAAUGUGACCAGCa 
                 126 
                 A-135551 
                 UGCUGGUCACAUUGAAAAGCUUc 
                 127 
                 332 
               
               
                   
               
               
                 AD-67644 
                 A-135570 
                 asgscuuuUfcAfAfUfgugaccagcaL96 
                 128 
                 A-135571 
                 usGfscugGfuCfAfcauuGfaA 
                 129 
                 332 
               
               
                   
                   
                   
                   
                   
                 faagcususc 
                   
                   
               
               
                   
               
               
                 AD-67654 
                 A-135570 
                 asgscuuuUfcAfAfUfgugaccagcaL96 
                 130 
                 A-135581 
                 UfsGfscugGfuCfAfcauuGfa 
                 131 
                 332 
               
               
                   
                   
                   
                   
                   
                 Afaagcususc 
                   
                   
               
               
                   
               
               
                 AD-67627 
                 A-135534 
                 Y44GCUUUUCAAUGUGACCAGCAa 
                 132 
                 A-135535 
                 UUGCUGGUCACAUUGAAAAGCUu 
                 133 
                 333 
               
               
                   
               
               
                 AD-67636 
                 A-135554 
                 gscsuuuuCfaAfUfGfugaccagcaaL96 
                 134 
                 A-135555 
                 usUfsgcuGfgUfCfacauUfgA 
                 135 
                 333 
               
               
                   
                   
                   
                   
                   
                 faaagcsusu 
                   
                   
               
               
                   
               
               
                 AD-67646 
                 A-135554 
                 gscsuuuuCfaAfUfGfugaccagcaaL96 
                 136 
                 A-135573 
                 UfsUfsgcuGfgUfCfacauUfg 
                 137 
                 333 
               
               
                   
                   
                   
                   
                   
                 Afaaagcsusu 
                   
                   
               
               
                   
               
               
                 AD-67658 
                 A-135590 
                 CACACUGAGAAUCAACACAAa 
                 138 
                 A-135591 
                 UUUGUGUUGAUUCUCAGUGUGCa 
                 139 
                 351 
               
               
                   
               
               
                 AD-67657 
                 A-135586 
                 CCAAAUGAAAGGACUCACUUa 
                 140 
                 A-135587 
                 UAAGUGAGUCCUUUCAUUUGGAg 
                 141 
                 469 
               
               
                   
               
               
                 AD-67632 
                 A-135546 
                 Y44UACACAUUUGGAGGAGACGUa 
                 142 
                 A-135547 
                 UACGUCUCCUCCAAAUGUGUAUc 
                 143 
                 618 
               
               
                   
               
               
                 AD-67642 
                 A-135566 
                 usascacaUfuUfGfGfaggagacguaL96 
                 144 
                 A-135567 
                 usAfscguCfuCfCfuccaAfaU 
                 145 
                 618 
               
               
                   
                   
                   
                   
                   
                 fguguasusc 
                   
                   
               
               
                   
               
               
                 AD-67652 
                 A-135566 
                 usascacaUfuUfGfGfaggagacguaL96 
                 146 
                 A-135579 
                 UfsAfscguCfuCfCfuccaAfa 
                 147 
                 618 
               
               
                   
                   
                   
                   
                   
                 Ufguguasusc 
                   
                   
               
               
                   
               
               
                 AD-67629 
                 A-135538 
                 Y44ACACAUUUGGAGGAGACGUAa 
                 148 
                 A-135539 
                 UUACGUCUCCUCCAAAUGUGUAu 
                 149 
                 619 
               
               
                   
               
               
                 AD-67638 
                 A-135558 
                 ascsacauUfuGfGfAfggagacguaaL96 
                 150 
                 A-135559 
                 usUfsacgUfcUfCfcuccAfaA 
                 151 
                 619 
               
               
                   
                   
                   
                   
                   
                 fugugusasu 
                   
                   
               
               
                   
               
               
                 AD-67648 
                 A-135558 
                 ascsacauUfuGfGfAfggagacguaaL96 
                 152 
                 A-135575 
                 UfsUfsacgUfcUfCfcuccAfa 
                 153 
                 619 
               
               
                   
                   
                   
                   
                   
                 Afugugusasu 
                   
                   
               
               
                   
               
               
                 AD-67631 
                 A-135544 
                 Y44CACAUUUGGAGGAGACGUAAu 
                 154 
                 A-135545 
                 AUUACGUCUCCUCCAAAUGUGUa 
                 155 
                 620 
               
               
                   
               
               
                 AD-67641 
                 A-135564 
                 csascauuUfgGfAfGfgagacguaauL96 
                 156 
                 A-135565 
                 asUfsuacGfuCfUfccucCfaA 
                 157 
                 620 
               
               
                   
                   
                   
                   
                   
                 faugugsusa 
                   
                   
               
               
                   
               
               
                 AD-67651 
                 A-135564 
                 csascauuUfgGfAfGfgagacguaauL96 
                 158 
                 A-135578 
                 AfsUfsuacGfuCfUfccucCfa 
                 159 
                 620 
               
               
                   
                   
                   
                   
                   
                 Afaugugsusa 
                   
                   
               
               
                   
               
               
                 AD-67675 
                 A-135630 
                 GAGACCUUGAUACUUUCAAAu 
                 160 
                 A-135631 
                 AUUUGAAAGUAUCAAGGUCUCCc 
                 161 
                 846 
               
               
                   
               
               
                 AD-67665 
                 A-135608 
                 UAAUUUGAGGGUCAGUUCCUa 
                 162 
                 A-135609 
                 UAGGAACUGACCCUCAAAUUAGg 
                 163 
                 976 
               
               
                   
               
               
                 AD-67633 
                 A-135548 
                 Y44UUCCUAUUUAUUUUGAGUCUa 
                 164 
                 A-135549 
                 UAGACUCAAAAUAAAUAGGAAAa 
                 165 
                 1093 
               
               
                   
               
               
                 AD-67643 
                 A-135568 
                 ususccuaUfuUfAfUfuuugagucuaL96 
                 166 
                 A-135569 
                 usAfsgacUfcAfAfaauaAfaU 
                 167 
                 1093 
               
               
                   
                   
                   
                   
                   
                 faggaasasa 
                   
                   
               
               
                   
               
               
                 AD-67653 
                 A-135568 
                 ususccuaUfuUfAfUfuuugagucuaL96 
                 168 
                 A-135580 
                 UfsAfsgacUfcAfAfaauaAfa 
                 169 
                 1093 
               
               
                   
                   
                   
                   
                   
                 Ufaggaasasa 
                   
                   
               
               
                   
               
               
                 AD-67640 
                 A-135562 
                 uscscuauUfuAfUfUfuugagucuguL96 
                 170 
                 A-135563 
                 asCfsagaCfuCfAfaaauAfaA 
                 171 
                 1094 
               
               
                   
                   
                   
                   
                   
                 fuaggasasa 
                   
                   
               
               
                   
               
               
                 AD-67650 
                 A-135562 
                 uscscuauUfuAfUfUfuugagucuguL96 
                 172 
                 A-135577 
                 AfsCfsagaCfuCfAfaaauAfa 
                 173 
                 1094 
               
               
                   
                   
                   
                   
                   
                 Afuaggasasa 
                   
                   
               
               
                   
               
               
                 AD-67663 
                 A-135604 
                 UUGAAGAUAUAUUGUAGUAGa 
                 174 
                 A-135605 
                 UCUACUACAAUAUAUCUUCAAAa 
                 175 
                 1157 
               
               
                   
               
               
                 AD-67676 
                 A-135632 
                 AUUGUAGUAGAUGUUACAAUu 
                 176 
                 A-135633 
                 AAUUGUAACAUCUACUACAAUAu 
                 177 
                 1167 
               
               
                   
               
               
                 AD-67666 
                 A-135610 
                 GUAUUUGUAAGGUGCUUGGUa 
                 178 
                 A-135611 
                 UACCAAGCACCUUACAAAUACUc 
                 179 
                 1245 
               
               
                   
               
               
                 AD-67661 
                 A-135596 
                 AAGCAUAAAGAUCAAACCGUa 
                 180 
                 A-135597 
                 AACGGUUUGAUCUUUAUGCUUCa 
                 181 
                 1293 
               
               
                   
               
               
                 AD-67669 
                 A-135618 
                 CCUUUAUUUAACCCAUUAAUa 
                 182 
                 A-135619 
                 UAUUAAUGGGUUAAAUAAAGGUg 
                 183 
                 1331 
               
               
                   
               
               
                 AD-67667 
                 A-135612 
                 AGGAAGCAAACAGAUUAAGUa 
                 184 
                 A-135613 
                 UACUUAAUCUGUUUGCUUCCUCa 
                 185 
                 1518 
               
               
                   
               
               
                 AD-67674 
                 A-135628 
                 CAGGCAUUGAAUCUACAGAUa 
                 186 
                 A-135629 
                 UAUCUGUAGAUUCAAUGCCUGGc 
                 187 
                 1682 
               
               
                   
               
               
                 AD-67655 
                 A-135582 
                 UGAUUCAAAAUUCAAAAGAUa 
                 188 
                 A-135583 
                 UAUCUUUUGAAUUUUGAAUCAUg 
                 189 
                 2103 
               
               
                   
               
               
                 AD-67672 
                 A-135624 
                 UCUAAAGAUAGUCUACAUUUa 
                 190 
                 A-135625 
                 UAAAUGUAGACUAUCUUUAGAAg 
                 191 
                 2220 
               
               
                   
               
               
                 AD-67659 
                 A-135592 
                 GGAAAUGUAUGUUAAAAGCAa 
                 192 
                 A-135593 
                 UUGCUUUUAACAUACAUUUCCAa 
                 193 
                 2240 
               
               
                   
               
               
                 AD-67673 
                 A-135626 
                 UGUUUUCUGCUUUCUGUCAAa 
                 194 
                 A-135627 
                 UUUGACAGAAAGCAGAAAACAAa 
                 195 
                 2648 
               
               
                   
               
               
                 AD-67664 
                 A-135606 
                 UUUCUGUCAAGUAUAAACUUa 
                 196 
                 A-135607 
                 UAAGUUUAUACUUGACAGAAAGc 
                 197 
                 2658 
               
               
                   
               
               
                 AD-67662 
                 A-135598 
                 UUCUGUCAAGUAUAAACUUCa 
                 198 
                 A-135599 
                 UGAAGUUUAUACUUGACAGAAAg 
                 199 
                 2659 
               
               
                   
               
               
                 AD-67671 
                 A-135622 
                 GUACUUGCAAAAUCACAUUUu 
                 200 
                 A-135623 
                 AAAAUGUGAUUUUGCAAGUACAg 
                 201 
                 2690 
               
               
                   
               
               
                 AD-67670 
                 A-135620 
                 UUCUUUGUGUGAAUUACAGGa 
                 202 
                 A-135621 
                 UCCUGUAAUUCACACAAAGAACa 
                 203 
                 3031 
               
               
                   
               
               
                 AD-67668 
                 A-135616 
                 UGUGGUGUUGGAUUUGUAAGa 
                 204 
                 A-135617 
                 UCUUACAAAUCCAACACCACAAg 
                 205 
                 3115 
               
               
                   
               
               
                 AD-67660 
                 A-135594 
                 UCCCUUUUGUCUCAUGUUUCa 
                 206 
                 A-135595 
                 UGAAACAUGAGACAAAAGGGAUa 
                 207 
                 3143 
               
               
                   
               
               
                 AD-67656 
                 A-135584 
                 CUGCAUUUGAUUGUCACUUUu 
                 208 
                 A-135585 
                 AAAAGUGACAAUCAAAUGCAGAa 
                 209 
                 3198 
               
               
                   
               
               
                 AD-67628 
                 A-135536 
                 Y44UACCUGCAUUAAUUUAAUAAa 
                 210 
                 A-135537 
                 UUUAUUAAAUUAAUGCAGGUACa 
                 211 
                 3221 
               
               
                   
               
               
                 AD-67637 
                 A-135556 
                 usasccugCfaUfUfAfauuuaauaaaL96 
                 212 
                 A-135557 
                 usUfsuauUfaAfAfuuaaUfgC 
                 213 
                 3221 
               
               
                   
                   
                   
                   
                   
                 fagguascsa 
                   
                   
               
               
                   
               
               
                 AD-67647 
                 A-135556 
                 usasccugCfaUfUfAfauuuaauaaaL96 
                 214 
                 A-135574 
                 UfsUfsuauUfaAfAfuuaaUfg 
                 215 
                 3221 
               
               
                   
                   
                   
                   
                   
                 Cfagguascsa 
                   
                   
               
               
                   
               
               
                 AD-67626 
                 A-135532 
                 Y44ACCUGCAUUAAUUUAAUAAAa 
                 216 
                 A-135533 
                 UUUUAUUAAAUUAAUGCAGGUAc 
                 217 
                 3222 
               
               
                   
               
               
                 AD-67635 
                 A-135552 
                 ascscugcAfuUfAfAfuuuaauaaaaL96 
                 218 
                 A-135553 
                 usUfsuuaUfuAfAfauuaAfuG 
                 219 
                 3222 
               
               
                   
                   
                   
                   
                   
                 fcaggusasc 
                   
                   
               
               
                   
               
               
                 AD-67645 
                 A-135552 
                 ascscugcAfuUfAfAfuuuaauaaaaL96 
                 220 
                 A-135572 
                 UfsUfsuuaUfuAfAfauuaAfu 
                 221 
                 3222 
               
               
                   
                   
                   
                   
                   
                 Gfcaggusasc 
               
               
                   
               
            
           
         
       
     
     EQUIVALENTS 
     Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments and methods described herein. Such equivalents are intended to be encompassed by the scope of the following claims.