Peptides binding to Bfl-1

1. A polypeptide that binds to Bfl-1, the polypeptide comprising:

(a) the amino acid sequence set forth in SEQ ID NO: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence;

(b) an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of ATQLRRFGDKLNFRQ (SEQ ID NO:121) and that selectively binds Bfl-1 over MCL-1, wherein at least two amino acids in the amino acid sequence of SEQ ID NO:121 are substituted by non-natural amino acids with olefinic side chains, wherein F at position 7 of the amino acid sequence of SEQ ID NO:121 is substituted with an amino acid with a bulkier side chain, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence;

(c) an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of an amino acid sequence set forth below:

(i)

(SEQ ID NO: 122)

AELEVECATQLRRFGDKLNFRQKLLN;

(ii)

(SEQ ID NO: 123)

EIWIAQELRRIGDEFNAYYARR;

(iii)

(SEQ ID NO: 124)

DIIRNIARHLAQVGDSMDRSI;

(iv)

(SEQ ID NO: 125)

SSTMGQVGRQLAIIGDDINRRY;

(v)

(SEQ ID NO: 126)

QDASTKKLSESLKRIGDELDSNMEL;

or

(vi)

(SEQ ID NO: 127)

RLAEVCAVLLRLGDELEMIR,

wherein the polypeptide selectively binds Bfl-1 over MCL-1;

wherein at least two amino acids in each amino acid sequence are substituted by non-natural amino acids with olefinic side chains,

wherein at least one cysteine if present in the polypeptide is optionally replaced by serine, and wherein at least one methionine if present in the polypeptide is optionally replaced by norleucine; and

wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus of the amino acid sequence;

(d) an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JATQLRRFGDKLNFRQKLL (SEQ ID NO: 128) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:128 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid;

(e) an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JEVESATQLRRFGDKLNFRQKLL (SEQ ID NO:129) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:129 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid;

(f) an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JIAQELRRIGDEFNAYYARR (SEQ ID NO: 130) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:130 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid;

(g) an amino acid sequence with 1 to 5 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1, and wherein the polypeptide comprises a non-natural amino acid bearings an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence; or

(h) an amino acid sequence with 1 to 5 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 128, wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence.

2. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 1 to the human subject.

3. The method of claim 2 , wherein a biological sample comprising a tumor from the human subject is or has previously been determined to express Bfl-1.

4. A pharmaceutical composition comprising the polypeptide of claim 1 , and a pharmaceutically acceptable carrier.

5. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering to the human subject a therapeutically effective amount of the pharmaceutical composition of claim 4 .

6. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence set forth in SEQ ID NQ: 22-36, 41-119, 184, 186, 195, 197, or 208, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence.

7. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 1 to 5 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

8. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 1 or 2 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NQ: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

9. The polypeptide of claim 1 , wherein the polypeptide is stapled.

10. A pharmaceutical composition comprising the polypeptide of claim 9 and a pharmaceutically acceptable carrier.

11. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 9 to the human subject.

12. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 1 to 5 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 128, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

13. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 2 to 3 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 128, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

14. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 22-25, 49-67, 184, or 186, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence.

15. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of ATQLRRFGDKLNFRQ (SEQ ID NO:121) and that selectively binds Bfl-1 over MCL-1, wherein at least two amino acids in the amino acid sequence of SEQ ID NO:121 are substituted by non-natural amino acids with olefinic side chains, wherein F at position 7 of the amino acid sequence of SEQ ID NO:121 is substituted with an amino acid with a bulkier side chain, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence.

16. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of ATQLRRFGDKLNFRQ (SEQ ID NO:121) and that selectively binds Bfl-1 over MCL-1, wherein at least two amino acids in the amino acid sequence of SEQ ID NO:121 are substituted by non-natural amino acids with olefinic side chains, wherein F at position 7 of the amino acid sequence of SEQ ID NO:121 is substituted with an amino acid with a bulkier side chain, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence.

17. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JATQLRRFGDKLNFRQKLL (SEQ ID NO: 128) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:128 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

18. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of JATQLRRFGDKLNFRQKLL (SEQ ID NO: 128) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:128 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

19. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JEVESATQLRRFGDKLNFRQKLL (SEQ ID NO:129) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:129 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

20. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of JEVESATQLRRFGDKLNFRQKLL (SEQ ID NO:129) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:129 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

21. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 50% identical to the Bfl-1 interacting alpha-helical face of JIAQELRRIGDEFNAYYARR (SEQ ID NO: 130) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:130 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

22. The polypeptide of claim 1 , wherein the polypeptide comprises the amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of JIAQELRRIGDEFNAYYARR (SEQ ID NO: 130) and that selectively binds Bfl-1 over MCL-1; wherein the polypeptide forms a covalent bond with Cys 55 of Bfl-1; wherein at least two amino acids in the amino acid sequence of SEQ ID NO:130 are substituted by non-natural amino acids with olefinic side chains, and wherein J is a non-natural amino acid bearing an electrophilic group, or an electrophilic warhead that does not comprise an amino acid.

23. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 1 to 5 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 22-25, 49-67, 184, or 186, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

24. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence with 1 or 2 amino acid substitutions relative to the amino acid sequence set forth in SEQ ID NO: 22-25, 49-67, 184, or 186, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or an electrophilic warhead at the N-terminus of the amino acid sequence, and wherein the polypeptide selectively binds Bfl-1 over MCL-1 and forms a covalent bond with Cys 55 of Bfl-1.

25. The polypeptide of claim 1 , wherein the non-natural amino acid bearing an electrophilic group or the electrophilic warhead at the N-terminus of the amino acid sequence is (S)-1-acryloylpyrrolidine-3-carboxamide, 1-acryloylpiperidine-4-carboxamide, (R)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpyrrolidine-2-carboxamide, (R)-1-acryloylpyrrolidine-2-carboxamide, (E)-4-(dimethylamino)but-2-enamide, or acrylamide.

26. The polypeptide of claim 1 , wherein the non-natural amino acid bearing an electrophilic group or the electrophilic warhead at the N-terminus of the amino acid sequence is (R)-1-acryloylpiperidine-3-carboxamide.

27. The polypeptide of claim 1 , wherein the polypeptide comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of an amino acid sequence set forth below:

(i)

(SEQ ID NO: 122)

AELEVECATQLRRFGDKLNFRQKLLN;

(ii)

(SEQ ID NO: 123)

EIWIAQELRRIGDEFNAYYARR;

(iii)

(SEQ ID NO: 124)

DIIRNIARHLAQVGDSMDRSI;

(iv)

(SEQ ID NO: 125)

SSTMGQVGRQLAIIGDDINRRY;

(v)

(SEQ ID NO: 126)

QDASTKKLSESLKRIGDELDSNMEL;

or

(vi)

(SEQ ID NO: 127)

RLAEVCAVLLRLGDELEMIR,

wherein the polypeptide selectively binds Bfl-1 over MCL-1;

wherein at least two amino acids in each amino acid sequence are substituted by non-natural amino acids with olefinic side chains,

wherein at least one cysteine if present in the polypeptide is optionally replaced by serine, and wherein at least one methionine if present in the polypeptide is optionally replaced by norleucine; and

wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus-of the amino acid sequence.

28. A polypeptide that binds to Bfl-1, the polypeptide comprising an amino acid sequence that is at least 70% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID N: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus in of the amino acid sequence.

29. A pharmaceutical composition comprising the polypeptide of claim 28 , and a pharmaceutically acceptable carrier.

30. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering to human subject therapeutically effective amount of the pharmaceutical composition of claim 29 .

31. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering to the human subject a therapeutically effective amount of the polypeptide of claim 28 .

32. The method of claim 31 , wherein a biological sample comprising a tumor from the human subject is or has previously been determined to express Bfl-1.

33. The polypeptide of claim 28 , wherein the poly comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID NO: 62, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus of the amino acid sequence.

34. The polypeptide of claim 33 , which is stapled.

35. A pharmaceutical composition comprising the polypeptide of claim 34 and a pharmaceutically acceptable carrier.

36. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 34 to the human subject.

37. The polypeptide of claim 28 , which is stapled.

38. A pharmaceutical composition comprising the polypeptide of claim 37 and a pharmaceutically acceptable carrier.

39. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 37 to the human subject.

40. The polypeptide of claim 28 , wherein the polypeptide comprises the amino acid sequence of:

(i)

(SEQ ID NO: 24)

JEVESATQLRXFGDXLNFRQKLL;

or

(ii)

(SEQ ID NO: 30)

JIAQELRXIGDXFNAYYARR;

wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid, and each X is a non-natural amino acid with an olefinic side chain.

41. The polypeptide of claim 40 , wherein the non-natural amino acid bearing an electrophilic group or the electrophilic warhead at the N-terminus of the amino acid sequence is (R)-1-acryloylpiperidine-3-carboxamide.

42. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 41 to the human subject.

43. A pharmaceutical composition comprising the polypeptide of claim 41 , and a pharmaceutically acceptable carrier.

44. The polypeptide of claim 28 , wherein the polypeptide comprises: (S)-1-acryloylpyrrolidine-3-carboxamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), 1-acryloylpiperidine-4-carboxamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), (R)-1-acryloylpiperidine-3-carboxamide-EVESATQLRXFGDXLNFRQKLL (SEQ ID NO: 186), (R)-1-acryloylpiperidine-3-carboxamide-EVESATQLRXFGDXLNFRQKLL (SEQ ID NO: 186)-Lys(biotin), (S)-1-acryloylpiperidine-3-carboxamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), (S)-1-acryloylpyrrolidine-2-carboxamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), (R)-1-acryloylpyrrolidine-2-carboxamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), (E)-4-(dimethylamino)but-2-enamide-EVES ATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), or acrylamide-EVESATQLRXFGDXLNFRQKLLK (SEQ ID NO: 184), wherein X indicates non-natural amino acids that are joined by an intramolecular cross-link.

45. The polypeptide of claim 28 , wherein polypeptide comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID NO: 22-36, 41-119, 184, 186, 195, 197, or 208, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus of the amino acid sequence.

46. The polypeptide of claim 28 , wherein polypeptide comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID NO: 62, wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group or a non-amino acid warhead at the N-terminus of the amino acid sequence.

47. The polypeptide of claim 28 , wherein the polypeptide comprises the amino acid sequence of:

(i) JGRQLAXIGDXINR (SEQ ID NO:72)

(ii) JGR8LAIIGDXINR (SEQ ID NO:79)

(iii) JVGRQLAXIGDXINR (SEQ ID NO:89)

(iv) JVGR8LAIIGDXINR (SEQ ID NO:96)

(v) JLSESLKXIGDXLDS (SEQ ID NO:107); or

(vi) JLSE8LKRIGDXLDS (SEQ ID NO:115);

wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid, each X is a non-natural amino acid with olefinic side chain, and 8 is R-octenyl alanine.

48. The polypeptide of claim 47 , wherein the polypeptide is stapled and each X is S-pentenyl-alanine.

49. A polypeptide that binds to Bfl-1, the polypeptide comprising the amino acid sequence JAT8LRRFGDXLNFRQ (SEQ ID NO:62) with 0 to 5 amino acid substitutions relative to the amino acid sequence of SEQ ID NO:62, wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid at the N-terminus of the amino acid sequence, 8 is R-octenyl alanine, and X is a non-natural amino acid with an olefinic side chain.

50. The polypeptide of claim 49 , wherein the polypeptide is stapled.

51. A pharmaceutical composition comprising the polypeptide of claim 50 and a pharmaceutically acceptable carrier.

52. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 50 to the human subject.

53. The polypeptide of claim 49 , wherein X is S-pentenyl alanine.

54. The polypeptide of claim 53 , wherein the polypeptide is stapled, and wherein the R-octenyl alanine is linked to the S-pentenyl alanine.

55. The polypeptide of claim 49 , wherein the polypeptide comprises the amino acid sequence JAT8LRRFGDXLNFRQ (SEQ ID NO:62) with 1 to 5 amino acid substitutions relative to the amino acid sequence of SEQ ID NO:62, wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid at the N-terminus of the amino acid sequence, 8 is R-octenyl alanine, and X is a non-natural amino acid with an olefinic side chain.

56. The polypeptide of claim 55 , wherein the polypeptide is stapled, wherein X is S-pentenyl alanine, and wherein the R-octenyl alanine is linked to the S-pentenyl alanine.

57. A pharmaceutical composition comprising the polypeptide of claim 56 and a pharmaceutically acceptable carrier.

58. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 56 to the human subject.

59. The polypeptide of claim 56 , wherein J is (S)-1-acryloylpyrrolidine-3-carboxamide, 1-acryloylpiperidine-4-carboxamide, (R)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpyrrolidine-2-carboxamide, (R)-1-acryloylpyrrolidine-2-carboxamide, (E)-4-(dimethylamino)but-2-enamide, or acrylamide.

60. The polypeptide of claim 56 , wherein J is (R)-1-acryloylpiperidine-3-carboxamide.

61. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 60 to the human subject.

62. A pharmaceutical composition comprising the polypeptide of claim 60 , and a pharmaceutically acceptable carrier.

63. The polypeptide of claim 49 , wherein the polypeptide comprises the amino acid sequence JAT8LRRFGDXLNFRQ (SEQ ID NO:62) with 1 or 2 amino acid substitutions relative to the amino acid sequence of SEQ ID NO:62, wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid at the N-terminus of the amino acid sequence, 8 is R-octenyl alanine, and X is a non-natural amino acid with an olefinic side chain.

64. The polypeptide of claim 63 , wherein the polypeptide is stapled, wherein X is S-pentenyl alanine, and wherein the R-octenyl alanine is linked to the S-pentenyl alanine.

65. A pharmaceutical composition comprising the polypeptide of claim 64 and a pharmaceutically acceptable carrier.

66. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 64 to the human subject.

67. The polypeptide of claim 64 , wherein J is (S)-1-acryloylpyrrolidine-3-carboxamide, 1-acryloylpiperidine-4-carboxamide, (R)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpiperidine-3-carboxamide, (S)-1-acryloylpyrrolidine-2-carboxamide, (R)-1-acryloylpyrrolidine-2-carboxamide, (E)-4-(dimethylamino)but-2-enamide, or acrylamide.

68. The polypeptide of claim 64 , wherein J is (R)-1-acryloylpiperidine-3-carboxamide.

69. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 68 to the human subject.

70. A pharmaceutical composition comprising the polypeptide of claim 68 , and a pharmaceutically acceptable carrier.

71. The polypeptide of claim 49 , wherein the polypeptide comprises the amino acid sequence JAT8LRRFGDXLNFRQ (SEQ ID NO:62), wherein J is a non-natural electrophile containing amino acid or an electrophilic warhead that does not comprise an amino acid at the N-terminus of the amino acid sequence, 8 is R-octenyl alanine, and X is a non-natural amino acid with an olefinic side chain.

72. A polypeptide that binds to Bfl-1, the polypeptide comprising an amino acid sequence that is at least 70% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID NO: 131, wherein the polypeptide selectively binds Bfl-1 over MCL-1; wherein at least two amino acids in the amino acid sequence are substituted by non-natural amino acids with olefinic side chains, wherein the at least two amino acids are separated by three or six amino acids, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group at the N-terminus of the amino acid sequence.

73. The polypeptide of claim 72 , which is stapled.

74. A pharmaceutical composition comprising the polypeptide of claim 73 and a pharmaceutically acceptable carrier.

75. A method for treating a human subject suffering from a cancer that exhibits expression of BFL-1 or dependency on BFL-1, the method comprising administering a therapeutically effective amount of the polypeptide of claim 73 to the human subject.

76. The polypeptide of claim 72 , wherein the polypeptide comprises an amino acid sequence that is at least 90% identical to the Bfl-1 interacting alpha-helical face of the amino acid sequence set forth in SEQ ID NO: 131, wherein the polypeptide selectively binds Bfl-1 over MCL-1; wherein at least two amino acids in the amino acid sequence are substituted by non-natural amino acids with olefinic side chains, wherein the at least two amino acids are separated by three or six amino acids, and wherein the polypeptide comprises a non-natural amino acid bearing an electrophilic group at the N-terminus of the amino acid sequence.