Methods and compositions for treatment of myotonic dystrophy

1. A chimeric polypeptide comprising: (i) a functional fragment of an MBNL1 polypeptide, wherein the MBNL1 polypeptide comprises an amino acid sequence that is at least 95% identical to SEQ ID NO: 3, and wherein the functional fragment comprises amino acids 1-248 of the MBNL1 polypeptide, and (ii) a targeting moiety, wherein the targeting moiety comprises an antibody or antigen-binding fragment, wherein the targeting moiety transits cellular membranes via an equilibrative nucleoside transporter 2 (ENT2) transporter; and wherein the chimeric polypeptide is capable of binding CUG repeats.

2. The chimeric polypeptide of claim 1 , wherein the antibody or antigen-binding fragment comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein the VH comprises an amino acid sequence that is at least 90% identical to the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises an amino acid sequence that is at least 90% identical to the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

3. The chimeric polypeptide of claim 2 , wherein the VH comprises an amino acid sequence that is at least 95% identical to the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises an amino acid sequence that is at least 95% identical to the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

4. The chimeric polypeptide of claim 3 , wherein the VH comprises the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

5. The chimeric polypeptide of claim 1 or 4 , wherein the functional fragment of the MBNL1 polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of SEQ ID NO: 3; and wherein the targeting moiety is a Fab′ fragment.

6. The chimeric polypeptide of claim 1 or 4 , comprising a functional fragment of an MBNL1 polypeptide, wherein the MBNL1 polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3.

7. The chimeric polypeptide of claim 6 , wherein the targeting moiety is a Fab′ fragment.

8. The chimeric polypeptide of claim 6 , wherein the targeting moiety is an antibody.

9. A composition comprising the chimeric polypeptide of claim 6 , and a pharmaceutically acceptable carrier.

10. The chimeric polypeptide of claim 6 , wherein the functional fragment of the MBNL1 polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of SEQ ID NO: 3.

11. The chimeric polypeptide of claim 10 , wherein the targeting moiety is a Fab′ fragment.

12. The chimeric polypeptide of claim 11 , wherein the functional fragment of the MBNL1 polypeptide comprising amino acid residues 1-250 of SEQ ID NO: 3.

13. The chimeric polypeptide of claim 10 , wherein the targeting moiety is an antibody.

14. A composition comprising the chimeric polypeptide of claim 10 , and a pharmaceutically acceptable carrier.

15. The chimeric polypeptide of claim 10 , wherein the functional fragment of the MBNL1 polypeptide comprising amino acid residues 1-250 of SEQ ID NO: 3.

16. The chimeric polypeptide of claim 1 , wherein the functional fragment of the MBNL1 polypeptide lacks a portion of the C-terminus.

17. The chimeric polypeptide of claim 1 , wherein the targeting moiety comprises an antibody.

18. The chimeric polypeptide of claim 1 , wherein the targeting moiety is an antigen-binding fragment.

19. The chimeric polypeptide of claim 18 , wherein the antigen-binding fragment is a single chain Fv fragment (scFv).

20. The chimeric polypeptide of claim 18 , wherein the antigen-binding fragment is a Fab′ fragment.

21. The chimeric polypeptide of claim 1 , wherein the chimeric polypeptide is produced by chemically conjugating the functional fragment of the MBNL1 polypeptide to the targeting moiety.

22. The chimeric polypeptide of claim 1 , wherein the chimeric polypeptide is produced by a recombinant vector encoding both the functional fragment of the MBNL1 polypeptide and the targeting moiety.

23. The chimeric polypeptide of claim 1 , wherein the antibody or antigen-binding fragment thereof is an antigen binding fragment of 3E10.

24. The chimeric polypeptide of claim 1 , wherein the chimeric polypeptide is produced recombinantly to recombinantly conjugate the functional fragment of the MBNL1 polypeptide to the targeting moiety.

25. The chimeric polypeptide of claim 24 , wherein the chimeric polypeptide is produced in a prokaryotic or eukaryotic cell.

26. The chimeric polypeptide of claim 1 , wherein the functional fragment of the MBNL1 polypeptide is conjugated or joined to the targeting moiety by a linker.

27. The chimeric polypeptide of claim 26 , wherein the targeting moiety is conjugated to the N-terminal or C-terminal amino acid of the functional fragment of the MBNL1 polypeptide.

28. The chimeric polypeptide of claim 1 , wherein the functional fragment of the MBNL1 polypeptide is conjugated or joined directly to the targeting moiety.

29. The chimeric polypeptide of claim 1 , wherein the targeting moiety promotes transport into muscle cells.

30. The chimeric polypeptide of claim 1 , wherein the targeting moiety promotes transport into neurons.

31. A composition comprising the chimeric polypeptide of claim 1 , and a pharmaceutically acceptable carrier.

32. A nucleic acid construct, comprising a nucleotide sequence that encodes a functional fragment of an MBNL1 polypeptide, wherein the MBNL1 polypeptide comprises an amino acid sequence that is at least 95% identical to SEQ ID NO: 3, wherein the functional fragment comprises amino acids 1-248 of the MBNL1 polypeptide, and wherein the functional fragment is operably linked to a nucleotide sequence that encodes a targeting moiety, wherein the targeting moiety comprises an antibody or antigen-binding fragment, wherein the targeting moiety transits cellular membranes via an equilibrative nucleoside transporter 2 (ENT2) transporter;

wherein the nucleic acid construct encodes a chimeric polypeptide having MBNL biological activity and having the targeting activity of the targeting moiety; and wherein the chimeric polypeptide is capable of binding CUG repeats.

33. The nucleic acid construct of claim 32 , wherein the targeting moiety promotes transport into muscle cells or neurons.

34. The nucleic acid construct of claim 32 , wherein the functional fragment of the MBNL polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of the MBNL1 polypeptide; and wherein the targeting moiety is a Fab′ fragment.

35. The nucleic acid construct of claim 34 , wherein the antibody or antigen-binding fragment comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein the VH comprises the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

36. The nucleic acid of claim 35 , wherein the chimeric polypeptide comprises a functional fragment of an MBNL1 polypeptide, wherein the MBNL1 polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3.

37. The nucleic acid of claim 36 , wherein the functional fragment of the MBNL1 polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of SEQ ID NO: 3.

38. The nucleic acid of claim 37 , wherein the targeting moiety is a Fab′ fragment.

39. The nucleic acid of claim 37 , wherein the targeting moiety is an antibody.

40. The nucleic acid of claim 36 , wherein the targeting moiety is a Fab′ fragment.

41. The nucleic acid of claim 36 , wherein the targeting moiety is an antibody.

42. A method of delivering a chimeric polypeptide into a cell, comprising contacting a cell with a chimeric polypeptide, which chimeric polypeptide comprises: (i) a functional fragment of an MBNL1 polypeptide, wherein the MBNL1 polypeptide comprises an amino acid sequence that is at least 95% identical to SEQ ID NO: 3, and wherein the functional fragment comprises amino acids 1-248 of the MBNL1 polypeptide, and (ii) a targeting moiety, wherein the targeting moiety comprises an antibody or antigen-binding fragment, wherein the targeting moiety transits cellular membranes via an equilibrative nucleoside transporter 2 (ENT2) transporter; and wherein the chimeric polypeptide is capable of binding CUG repeats.

43. The method of claim 42 , wherein the antibody or antigen-binding fragment is an antigen-binding fragment.

44. The method of claim 43 , wherein the antigen-binding fragment is a Fab′ fragment.

45. The method of claim 42 , wherein the cell is a muscle cell.

46. The method of claim 45 , wherein the muscle cell is a skeletal muscle cell.

47. The method of claim 45 , wherein the muscle cell is a cardiac muscle cell.

48. The method of claim 42 , wherein the cell is a neuron.

49. The method of claim 42 , wherein the chimeric polypeptide is produced by chemically conjugating the functional fragment of the MBNL polypeptide to the targeting moiety.

50. The method of claim 42 , wherein the functional fragment of the MBNL1 polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of SEQ ID NO: 3; wherein the antibody or antigen-binding fragment is a humanized variant of an antibody or antigen-binding fragment comprising a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein the VH comprises the amino acid sequence set forth in SEQ ID NO: 12 or a humanized variant thereof, and the VL comprises the amino acid sequence set forth in SEQ ID NO: 14 or a humanized variant thereof.

51. A chimeric polypeptide comprising: (i) a functional fragment of an MBNL1 polypeptide, wherein the functional fragment comprises amino acids 1-248 of a human MBNL1 polypeptide, and (ii) a targeting moiety, wherein the targeting moiety comprises an antibody or antigen-binding fragment, wherein the targeting moiety transits cellular membranes via an equilibrative nucleoside transporter 2 (ENT2) transporter; and wherein the chimeric polypeptide is capable of binding CUG repeats.

52. The chimeric polypeptide of claim 51 , wherein the antibody or antigen-binding fragment comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein the VH comprises an amino acid sequence that is at least 90% identical to the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises an amino acid sequence that is at least 90% identical to the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

53. The chimeric polypeptide of claim 52 , wherein the VH comprises the amino acid sequence set forth in SEQ ID NO: 12, and the VL comprises the amino acid sequence set forth in SEQ ID NO: 14, or which is a humanized antibody or antigen-binding fragment thereof.

54. The chimeric polypeptide of claim 53 , wherein the targeting moiety comprises an antibody.

55. The chimeric polypeptide of claim 53 , wherein the targeting moiety is a Fab′ fragment.

56. The chimeric polypeptide of claim 51 , wherein the functional fragment of the MBNL1 polypeptide is at least 250 amino acids in length and lacks a portion of the C-terminus of a human MBNL1 polypeptide.