Compositions and methods of treating facioscapulohumeral muscular dystrophy

1. A method of delivering an oligonucleotide to a subject, wherein the subject has facioscapulohumeral muscular dystrophy (FSHD), the method comprising intravenously administering to the subject a conjugate that comprises an anti-transferrin receptor antibody covalently linked to a 5′ end or a 3′ end of an oligonucleotide, wherein the oligonucleotide comprises one or more modifications and a strand that comprises a region of complementarity of at least 15 nucleotides in length to the nucleotide sequence of DUX4 mRNA;

wherein the oligonucleotide is in the range of 15-35 nucleotides in length; wherein the one or more modifications comprise a 2′-modified nucleoside selected from the group consisting of a 2′-O-methyl nucleoside, a 2′-fluoro nucleoside, a 2′-O-methoxyethyl nucleoside, and 2′,4′-bridged nucleosides, and combinations thereof, and/or comprise a modified backbone selected from a backbone comprising one or more phosphorothioate linkages and a phosphorodiamidate morpholino backbone; and

wherein the oligonucleotide brings about degradation of DUX4 mRNA as measured by the decreased expression of DUX4 biomarker RNAs comprising ZSCAN4 and LEUTX in the muscle cell.

2. The method of claim 1 , wherein the region of complementarity is at least 20 nucleotides in length.

3. The method of claim 1 , wherein the oligonucleotide is covalently linked to a lysine in the anti-transferrin receptor antibody via a cleavable linker.

4. The method of claim 3 , wherein the cleavable linker comprises a valine-citrulline sequence.

5. The method of claim 4 , wherein the cleavable linker further comprises one or more polyethylene glycol units.

6. The method of claim 1 , wherein the anti-transferrin receptor antibody is in the form of a ScFv, Fab fragment, Fab′ fragment, F(ab′)2 fragment, or Fv fragment.

7. The method of claim 1 , wherein the anti-transferrin receptor antibody is in the form of a Fab fragment.

8. The method of claim 1 , wherein the subject has one or more deletions of D4Z4 repeats in chromosome 4.

9. The method of claim 8 , wherein the subject has 10 or fewer D4Z4 repeats.

10. The method of claim 1 , wherein the muscle cell is a skeletal muscle cell, a cardiac muscle cell, or a smooth muscle cell.

11. The method of claim 1 , wherein the subject is human.

12. A method of delivering an oligonucleotide to a subject, wherein the subject has a muscular dystrophy associated with mutation of a repeat region, the method comprising intravenously administering to the subject a conjugate that comprises an anti-transferrin receptor antibody covalently linked to a 5′ end or a 3′ end of an oligonucleotide, wherein the oligonucleotide comprises one or more modifications and a strand that comprises a region of complementarity of at least 15 nucleotides in length to an RNA encoded by a gene associated with the muscular dystrophy;

wherein the mutation of the repeat region results in aberrant gene expression, wherein the oligonucleotide is in the range of 15-35 nucleotides in length; wherein the one or more modifications comprise a 2′-modified nucleoside selected from the group consisting of a 2′-O-methyl nucleoside, a 2′-fluoro nucleoside, a 2′-O-methoxyethyl nucleoside, and 2′,4′-bridged nucleosides, and/or comprise a modified backbone selected from a backbone comprising one or more phosphorothioate linkages and a phosphorodiamidate morpholino backbone; and

wherein the oligonucleotide brings about degradation of the RNA encoded by the gene associated with muscular dystrophy as measured by the decreased expression of DUX4 biomarker RNAs comprising ZSCAN4 and LEUTX downstream of the RNA encoded by the gene associated with muscular dystrophy in the muscle cell.

13. The method of claim 12 , wherein the anti-transferrin receptor antibody comprises a HCDR1, a HCDR2, a HCDR3, a LCDR1, a LCDR2, and a LCDR3, wherein the HCDR1 comprises SEQ ID NO: 281, the HCDR2 comprises SEQ ID NO: 282, 284, or 285, the HCDR3 comprises SEQ ID NO: 283, the LCDR1 comprises SEQ ID NO: 286 or 291, the LCDR2 comprises SEQ ID NO: 287, 289 or 292, and the LCDR3 comprises SEQ ID NO: 288 or 290.

14. The method of claim 12 , wherein the muscular dystrophy is facioscapulohumeral muscular dystrophy.

15. The method of claim 12 , wherein the muscular dystrophy is myotonic dystrophy.

16. The method of claim 12 , wherein the DUX4 biomarker RNAs further comprise one or more biomarker RNA selected from a group consisting of MBD3L2, TRIM43, PRAMEF1, and KHDC1L.