Compositions and methods of treating Facioscapulohumeral muscular dystrophy

1. A method of treating facioscapulohumeral muscular dystrophy (FSHD) in a subject comprising administering to the subject a therapeutic amount of an siRNA-antibody conjugate comprising an anti-transferrin receptor antibody or antigen binding fragment thereof conjugated to an siRNA molecule comprising a sense strand and an antisense strand, wherein the antisense strand is from 19 to 30 nucleotides in length and comprises a sequence selected from SEQ ID NOs: 72, 76, 126, 131, 132, 134-136, 212, 216, 266, 271, 272, and 274-276, and wherein the siRNA-antibody conjugate mediates RNA interference against human DUX4 mRNA and mediates downregulation of one or more DUX4 regulated genes, thereby treating FSHD in the subject.

2. The method of claim 1 , wherein the anti-transferrin receptor antibody or antigen binding fragment thereof binds to a transferrin receptor on a cell surface of a muscle cell.

3. The method of claim 1 , wherein the siRNA-antibody conjugate is delivered to a muscle cell of the subject.

4. The method of claim 2 , wherein the muscle cell expresses human DUX4 mRNA.

5. The method of claim 4 , wherein expression levels of human DUX4 mRNA are reduced by the siRNA-antibody conjugate.

6. The method of claim 1 , wherein the FSHD is caused by genetic and epigenetic changes in D4Z4 DNA region of long arm of chromosome 4 in muscle cells of the subject.

7. The method of claim 1 , wherein the FSHD is associated with muscle atrophy.

8. The method of claim 1 , wherein the RNA interference against the human DUX4 mRNA prevents or prevents progress of muscle atrophy in the subject.

9. The method of claim 1 , wherein the FSHD is FSHD type 1 or FSHD type 2.

10. The method of claim 1 , wherein the siRNA-antibody conjugate is formulated for parenteral administration.

11. The method of claim 1 , wherein the siRNA molecule comprises at least one 2′ modified nucleotide, at least one modified internucleotide linkage, or at least one inverted abasic moiety.

12. The method of claim 1 , wherein the sense strand and the antisense strand each independently comprises at least one 2′ modified nucleotide, at least one modified internucleotide linkage, or at least one inverted abasic moiety.

13. The method of claim 1 , wherein the antisense strand hybridizes to at least 8 contiguous bases of a target sequence of the human DUX4 mRNA.

14. The method of claim 1 , wherein the siRNA-antibody conjugate comprises a linker connecting the anti-transferrin receptor antibody or antigen binding fragment thereof to the siRNA molecule.

15. The method of claim 11 , wherein the at least one 2′ modified nucleotide comprises 2′-O-methyl, 2′-O-methoxyethyl (2′-O-MOE), 2′-O-aminopropyl, 2′-deoxy, 2′-deoxy-2′-fluoro, 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA) modified nucleotide, comprises locked nucleic acid (LNA) or ethylene nucleic acid (ENA), or comprises a combination thereof.

16. The method of claim 11 , wherein the at least one modified internucleotide linkage comprises a phosphorothioate linkage or a phosphorodithioate linkage.

17. The method of claim 11 , wherein the siRNA molecule comprises 3 or more 2′ modified nucleotides selected from 2′-O-methyl modified nucleotide and 2′-deoxy-2′-fluoro modified nucleotide.

18. The method of claim 11 , wherein the siRNA molecule comprises a 5′-terminal vinylphosphonate modified nucleotide.

19. The method of claim 1 , wherein the siRNA-antibody conjugate has a siRNA molecule to antibody ratio of 1 to 4.

20. The method of claim 1 , wherein the sense strand of the siRNA molecule comprises a sequence selected from SEQ ID NOs: 2, 6, 56, 61, 62, 64-66, 142, 146, 196, 201, 202, and 204-206.

21. The method of claim 1 , wherein the siRNA-antibody conjugate reduces expression of the one or more DUX4 regulated genes selected from MBD3L2, TRIM43, PRAMEF1, ZSCAN4, KHDC1L, and LEUTX.