Anti-PMEL17 antibodies and immunoconjugates

1. An immunoconjugate comprising an antibody that binds PMEL17 and a cytotoxic agent, wherein the antibody comprises:

a) (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 3, (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 4, (iii) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 5, (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 6, (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 7, and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 8; or

b) (i) HVR-H1 comprising the amino acid sequence of SEQ ID NO: 13, (ii) HVR-H2 comprising the amino acid sequence of SEQ ID NO: 14, and (iii) HVR-H3 comprising the amino acid sequence of SEQ ID NO: 15, (iv) HVR-L1 comprising the amino acid sequence of SEQ ID NO: 16, (v) HVR-L2 comprising the amino acid sequence of SEQ ID NO: 7, and (vi) HVR-L3 comprising the amino acid sequence of SEQ ID NO: 8; or

c) HVR-H1, HVR-H2, HVR-H3, HVR-L1, HVR-L2, and HVR-L3 of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862.

2. The immunoconjugate of claim 1 , wherein the antibody comprises:

a) a VH sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 1; or

b) a VL sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 2; or

c) a VH sequence as in (a) and a VL sequence as in (b); or

d) a VH sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 9; or

e) a VL sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10; or

f) a VH sequence as in (d) and a VL sequence as in (e); or

g) a VH sequence having at least 95% sequence identity to the VH sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862; or

h) a VL sequence having at least 95% sequence identity to the VL sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862; or

i) a VH sequence as in (g) and a VL sequence as in (h).

3. The immunoconjugate of claim 2 , comprising a VH sequence having the amino acid sequence of SEQ ID NO: 1, a VH sequence having the amino acid sequence of SEQ ID NO: 9, or a VH sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862.

4. The immunoconjugate of claim 2 , comprising a VL sequence having the amino acid sequence of SEQ ID NO: 2, a VL sequence having the amino acid sequence of SEQ ID NO: 10, or a VL sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862.

5. The immunoconjugate of claim 1 , comprising (a) a VH sequence having the amino acid sequence of SEQ ID NO: 1 and a VL sequence having the amino acid sequence of SEQ ID NO: 2; or (b) a VH sequence having the amino acid sequence of SEQ ID NO: 9 and a VL sequence having the amino acid sequence of SEQ ID NO: 10; or (c) a VH sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862 and a VL sequence of the antibody produced by hybridoma 7509(31D1.6.7) having ATCC Accession No. PTA-12862.

6. The immunoconjugate of claim 1 , which is an IgG1, IgG2a or IgG2b antibody.

7. The immunoconjugate of claim 1 having the formula Ab-(L-D)p, wherein:

(a) Ab is the antibody;

(b) L is a linker;

(c) D is a cytotoxic agent; and

(d) p ranges from 1-8.

8. The immunoconjugate of claim 7 , wherein D is an auristatin.

9. The immunoconjugate of claim 8 , wherein D has formula D E

and wherein R 2 and R 6 are each methyl, R 3 and R 4 are each isopropyl, R 5 is H, R 7 is sec-butyl, each R 8 is independently selected from CH 3 , O—CH 3 , OH, and H; R 9 is H; and R 18 is —C(R 8 ) 2 —C(R 8 ) 2 -aryl.

10. The immunoconjugate of claim 7 , wherein the drug is MMAE.

11. The immunoconjugate of claim 7 , wherein D is a pyrrolobenzodiazepine of Formula A:

wherein the dotted lines indicate the optional presence of a double bond between C1 and C2 or C2 and C3;

R 2 is independently selected from H, OH, ═O, ═CH 2 , CN, R, OR, ═CH—R D , ═C(R D ) 2 , O—SO 2 —R, CO 2 R and COR, and optionally further selected from halo or dihalo, wherein R D is independently selected from R, CO 2 R, COR, CHO, CO 2 H, and halo;

R 6 and R 9 are independently selected from H, R, OH, OR, SH, SR, NH 2 , NHR, NRR′, NO 2 , Me 3 Sn and halo;

R 7 is independently selected from H, R, OH, OR, SH, SR, NH 2 , NHR, NRR′, NO 2 , Me 3 Sn and halo;

Q is independently selected from O, S and NH;

R 11 is either H, or R or, where Q is O, SO 3 M, where M is a metal cation;

R and R′ are each independently selected from optionally substituted C 1-8 alkyl, C 3-8 heterocyclyl and C 5-20 aryl groups, and optionally in relation to the group NRR′, R and R′ together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring;

R 12 , R 16 , R 19 and R 17 are as defined for R 2 , R 6 , R 9 and R 7 respectively;

R″ is a C 3-12 alkylene group, which chain may be interrupted by one or more heteroatoms and/or aromatic rings that are optionally substituted; and

X and X′ are independently selected from O, S and N(H).

12. The immunoconjugate of claim 11 , wherein D has a structure selected from:

wherein R E and R E″ are each independently selected from H or R D , wherein R D is independently selected from R, CO 2 R, COR, CHO, CO 2 H, and halo;

wherein Ar 1 and Ar 3 are each independently optionally substituted C 5-20 aryl; and

wherein n is 0 or 1.

13. The immunoconjugate of claim 7 , wherein D is a pyrrolobenzodiazepine of Formula B:

wherein the horizontal wavy line indicates the covalent attachment site to the linker;

R V1 and R V2 are independently selected from H, methyl, ethyl, phenyl, fluoro-substituted phenyl, and C 5-6 heterocyclyl; and

n is 0 or 1.

14. The immunoconjugate of claim 7 , wherein D is a nemorubicin derivative.

15. The immunoconjugate of claim 14 , wherein D has a structure selected from:

16. The immunoconjugate of claim 7 , wherein the linker is cleavable by a protease.

17. The immunoconjugate of claim 16 , wherein the linker comprises a val-cit dipeptide or a Phe-Lys dipeptide.

18. The immunoconjugate of claim 7 , wherein the linker is acid-labile.

19. The immunoconjugate of claim 18 , wherein the linker comprises hydrazone.

20. The immunoconjugate of claim 7 having the formula:

wherein S is a sulfur atom.

21. The immunoconjugate of claim 7 having the formula:

22. The immunoconjugate of claim 7 having a formula selected from:

23. The immunoconjugate of claim 7 , wherein p ranges from 2-5.

24. A pharmaceutical formulation comprising the immunoconjugate of claim 1 and a pharmaceutically acceptable carrier.

25. A method of treating an individual having a PMEL17-positive cancer, the method comprising administering to the individual an effective amount of the immunoconjugate of claim 1 .

26. The method of claim 25 , wherein the PMEL17-positive cancer is melanoma.

27. The method of claim 26 , further comprising administering an additional therapeutic agent to the individual.

28. A method of inhibiting proliferation of a PMEL17-positive cell, the method comprising exposing the cell to the immunoconjugate of claim 1 under conditions permissive for binding of the immunoconjugate to PMEL17 on the surface of the cell, thereby inhibiting proliferation of the cell.

29. The method of claim 28 , wherein the cell is a melanoma cell.

30. A method of treating an individual having a PMEL17-positive cancer, wherein the PMEL17-positive cancer is resistant to a first therapeutic, the method comprising administering to the individual an effective amount of the immunoconjugate of claim 1 .

31. The method of claim 30 , wherein the PMEL17-positive cancer is melanoma.

32. The method of claim 30 , wherein the first therapeutic comprises a first antibody that binds an antigen other than PMEL17.

33. The method of claim 32 , wherein the first therapeutic is a first immunoconjugate comprising a first antibody that binds an antigen other than PMEL17 and a first cytotoxic agent.

34. The method of claim 32 , wherein the first antibody binds an antigen selected from endothelin B receptor (ETBR), tyrosinase-related protein 1 (TYRP1), cytotoxic T lymphocyte antigen 4 (CTLA-4), and glycoprotein NMB (GPNMB).

35. The method of claim 34 , wherein the first antibody binds ETBR.

36. The method of claim 35 , wherein the first antibody is hu5E9.v1.

37. The method of claim 33 , wherein the first immunoconjugate is hu5E9.v1-MC-val-cit-PAB-MMAE.

38. The method of claim 33 , wherein the first cytotoxic agent and the cytotoxic agent of the immunoconjugate comprising an antibody that binds PMEL17 are different.

39. The method of claim 38 , wherein the first cytotoxic agent is MMAE and the cytotoxic agent of the immunoconjugate comprising an antibody that binds PMEL17 is selected from a calicheamicin, a pyrrolobenzodiazepine, and a nemorubicin derivative.

40. The method of claim 39 , wherein the cytotoxic agent of the immunoconjugate comprising an antibody that binds PMEL17 is selected from a pyrrolobenzodiazepine and a nemorubicin derivative.

41. A method of treating an individual with PMEL17-positive cancer, comprising administering to the individual an effective amount of a first immunoconjugate of claim 1 in combination with a second immunoconjugate comprising an antibody that binds ETBR.

42. The method of claim 41 , wherein the antibody that binds ETBR comprises:

a) an HVR H1 comprising a sequence of SEQ ID NO: 33, an HVR H2 comprising a sequence of SEQ ID NO: 34, an HVR H3 comprising a sequence of SEQ ID NO: 35, an HVR L1 comprising a sequence of SEQ ID NO: 36, an HVR L2 comprising a sequence of SEQ ID NO: 37, and an HVR L3 comprising a sequence of SEQ ID NO: 38; or

b) a heavy chain variable region comprising the sequence of SEQ ID NO: 40 and a light chain variable region comprising the sequence of SEQ ID NO: 39.

43. The method of claim 41 , wherein the first immunoconjugate comprises a cytotoxic agent selected from an auristatin, a pyrrolobenzodiazepine, and a nemorubicin derivative, and the second immunoconjugate comprises a cytotoxic agent selected from an auristatin, a pyrrolobenzodiazepine, and a nemorubicin derivative.

44. The method of claim 41 , wherein the first immunoconjugate comprises a cytotoxic agent selected from a pyrrolobenzodiazepine and a nemorubicin derivative, and the second immunoconjugate comprises an auristatin.

45. The method of claim 44 , wherein the second immunoconjugate comprises MMAE.

46. The method of claim 41 , wherein the second immunoconjugate comprises a linker-drug portion comprising MC-val-cit-PAB-MMAE.

47. The method of claim 41 , wherein the second immunoconjugate is hu5E9.v1-MC-val-cit-PAB-MMAE.

48. The method of claim 41 , wherein the PMEL17-positive cancer is melanoma.

49. The method of claim 41 , wherein the PMEL17-positive cancer is also ETBR-positive.