Prodrugs activated by caspase

1. A chemotherapeutic prodrug conjugate comprising:

(i) an albumin-binding moiety that prolongs plasma circulation of the conjugate, joined directly or through a linker to

(ii) a caspase-cleavable peptide linker, wherein the four C-terminal amino acid residues of the caspase-cleavable peptide linker are selected from Asp-Xaa-Xaa-Asp (SEQ ID NO:1), Leu-Xaa-Xaa-Asp (SEQ ID NO:2), and Val-Xaa-Xaa-Asp (SEQ ID NO:3), where Xaa represents any amino acid residue, joined directly or through a linker to

(iii) a chemotherapeutic agent.

2. The conjugate of claim 1 , wherein the albumin-binding moiety is selected from the group consisting of maleimide, N-hydroxysuccinimide ester, halogenacetamide, halogenacetate, aziridine, disulfide, acetylene, pyridylthiol, oleate, and vinylcarbonyl.

3. The conjugate of claim 1 , wherein the functional albumin-binding moiety is maleimide.

4. The conjugate of claim 1 , wherein the caspase-cleavable peptide linker is cleavable by a caspase selected from the group consisting of caspase-3, caspase-7, and caspase-9.

5. The conjugate of claim 1 , wherein the four C-terminal amino acid residues of the caspase-cleavable peptide linker are selected from the group consisting of Asp-Glu-Val-Asp (SEQ ID NO:4), Asp-Leu-Val-Asp (SEQ ID NO:5) Asp-Glu-Ile-Asp (SEQ ID NO:6), and Leu-Glu-His-Asp (SEQ ID NO:7).

6. The conjugate of claim 5 , wherein the six C-terminal amino acid residues of the caspase-cleavable peptide linker consist of Lys-Gly-Asp-Glu-Val-Asp (SEQ ID NO:8).

7. The conjugate of claim 1 , wherein the chemotherapeutic agent induces apoptosis of tumor cells.

8. The conjugate of claim 1 , wherein the chemotherapeutic agent is selected from the group consisting of anthracyclines, antibiotics, alkylating agents, platinum-based agents, antimetabolites, topoisomerase inhibitors, and mitotic inhibitors.

9. The conjugate of claim 1 , wherein the chemotherapeutic agent is selected from the group consisting of doxorubicin, daunorubicin, epirubicin, idarubicin, valrubicin, and derivatives thereof.

10. The conjugate of claim 1 , wherein the chemotherapeutic agent is selected from the group consisting of actinomycin-D, bleomycin, mitomycin-C, calicheamicin, and derivatives thereof.

11. The conjugate of claim 1 , wherein the chemotherapeutic agent is selected from the group consisting of cyclophosphamide, mechlorethamine, uramustine, melphalan, chlorambucil, ifosfamide, bendamustine, carmustine, lomustine, streptozocin, busulfan, dacarbazine, temozolomide, thiotepa, altretamine, duocarmycin, cisplatin, carboplatin, nedaplatin, oxaliplatin, satraplatin, triplatin tetranitrate, 5-fluorouracil, 6 mercaptopurine, capecitabine, cladribine, clofarabine, cystarbine, floxuridine, fludarabine, gemcitabine, hydroxyurea, methotrexate, pemetrexed, pentostatin, thioguanine, camptothecin, topotecan, irinotecan, etoposide, teniposide, mitoxantrone, paclitaxel, docetaxel, izabepilone, vinblastine, vincristine, vindesine, vinorelbine, estramustine, maytansine, DM1 (mertansine), DM4, dolastatin, auristatin E, auristatin F, monomethyl auristatin E, monomethyl auristatin F, and derivatives thereof.

12. The conjugate of claim 1 , wherein the albumin-binding is maleimide, the caspase-cleavable peptide linker has an amino acid sequence consisting of Lys-Gly-Asp-Glu-Val-Asp (SEQ ID NO:8), and the chemotherapeutic agent is doxorubicin.

13. The conjugate of claim 1 , selected from the group consisting Maleimide-KGDEVD-PABC-Doxorubicin (SEQ ID NO: 10), Maleimide-KGDEVD-PABC-Daunorubicin (SEQ ID NO: 11), Maleimide-KGDEVD-PABC-Paclitaxel (SEQ ID NO: 12), Maleimide-KGDEVD-PABC-MMAE (SEQ ID NO: 13), Maleimide-DEVD-PABC-Doxorubicin (SEQ ID NO: 14), Maleimide-DEID-PABC-Doxorubicin (SEQ ID NO: 15), Maleimide-DLVD-PABC-Doxorubicin (SEQ ID NO: 16), Maleimide-DEVD-Doxorubicin (SEQ ID NO: 17), Maleimide-DEVD-MMAE (SEQ ID NO: 29), Pyridyldithiol-KGDEVD-PABC-Doxorubicin (SEQ ID NO: 18), Oleate-KGDEVD-PABC-Doxorubicin (SEQ ID NO: 19), and HSA-Maleimide-KGDEVD-PABC-Doxorubicin (SEQ ID NO: 28).

14. A chemotherapeutic prodrug conjugate comprising:

(i) a caspase-cleavable peptide, wherein the four C-terminal amino acid residues of the caspase-cleavable peptide linker are selected from Asp-Xaa-Xaa-Asp (SEQ ID NO:1), Leu-Xaa-Xaa-Asp (SEQ ID NO:2), and Val-Xaa-Xaa-Asp (SEQ ID NO:3), where Xaa represents any amino acid residue, joined directly or through a linker to

(ii) daunorubicin, joined directly or through a linker at its 14-CH 3 to

(iii) an albumin-binding moiety that prolongs plasma circulation of the conjugate.

15. A composition comprising the conjugate of claim 1 or claim 14 and a pharmaceutically acceptable carrier.

16. The composition of claim 1 or claim 14 , formulated for intravenous administration.

17. A method of amplifying apoptosis in tumor cells in a subject comprising:

inducing apoptosis in tumor cells thereby inducing expression of caspase; and

administering to the subject a conjugate according to claim 1 or claim 14 .

18. The method of claim 17 , wherein apoptosis is induced before and, optionally, after, the conjugate is administered.

19. The method of claim 17 , wherein the apoptosis is induced by a treatment selected from the group consisting of radiation, hyperthermia, laser therapy, photodynamic therapy, chemotherapy, and cryosurgery.

20. The method of claim 17 , wherein the apoptosis is induced by treatment by a targeted therapy using an agent that targets tumor cells.

21. The method of claim 17 , wherein the apoptosis is induced by treatment with a chemotherapeutic agent selected from the group consisting anthracyclines, antibiotics, alkylating agents, platinum-based agents, antimetabolites, topoisomerase inhibitors, and mitotic inhibitors.

22. The method of claim 17 , wherein the apoptosis is induced by radiation therapy.

23. The method of claim 22 , wherein the radiation therapy is effected before the conjugate is administered.

24. The method of claim 22 , wherein the radiation therapy is selected from the group consisting of gamma-knife radiation, cyber-knife radiation, and high intensity focused ultrasound radiation.

25. The method of claim 22 , wherein the radiation is applied at a dose of up to about 70 Gy.

26. The method of claim 22 , wherein the radiation is applied as a single dose of up to about 35 Gy.

27. The method of claim 22 , wherein the radiation therapy is applied at weekly doses of up to about 10 Gy.

28. The method of claim 17 , wherein the conjugate is administered intravenously.

29. A method of amplifying apoptosis in tumor cells in a subject, comprising administering a conjugate according to claim 1 to a subject in need thereof who has been treated with a first apoptosis inducing treatment effective to induce expression of caspase.

30. The method of claim 29 , wherein the apoptosis inducing treatment is selected from a group consisting of radiation, hyperthermia, laser therapy, photodynamic therapy, chemotherapy, and cryosurgery.

31. The method of claim 29 , wherein the apoptosis inducing treatment is targeted therapy using an agent that targets tumor cells.

32. The method of claim 29 , wherein the apoptosis is induced treatment with a chemotherapeutic agent selected from the group consisting of anthracyclines, antibiotics, alkylating agents, platinum-based agents, antimetabolites, topoisomerase inhibitors, and mitotic inhibitors.

33. The method of claim 30 , wherein the apoptosis inducing treatment is radiation therapy.

34. The method of claim 29 , further comprising, after administering the conjugate, treating the subject with a second apoptosis inducing treatment effective to induce expression of caspase.

35. The method of claim 34 , wherein the second apoptosis inducing treatment is the same as the first apoptosis inducing treatment.

36. The method of claim 34 , wherein the second apoptosis inducing treatment is different from the first apoptosis inducing treatment.

37. A method of treating cancer in a subject in need thereof comprising:

treating the subject with an apoptosis inducing treatment effective to induce expression of caspase; and

administering to the subject a conjugate according to claim 1 .

38. The method of claim 37 , wherein the apoptosis inducing treatment is effected before the conjugate is administered.

39. The method of claim 37 , wherein the apoptosis inducing treatment is selected from a group consisting of radiation, hyperthermia, laser therapy, photodynamic therapy, chemotherapy, and cryosurgery.

40. The method of claim 37 , wherein the apoptosis inducing treatment is targeted therapy using an agent that targets the cancer.

41. The method of claim 37 , wherein the apoptosis is induced treatment with a chemotherapeutic agent selected from the group consisting of anthracyclines, antibiotics, alkylating agents, platinum-based agents, antimetabolites, topoisomerase inhibitors, and mitotic inhibitors.

42. The method of claim 37 , wherein the apoptosis inducing treatment is radiation therapy.

43. A method of treating cancer comprising administering a conjugate according to claim 1 to a subject in need thereof who has been treated with a first apoptosis inducing treatment effective to induce expression of caspase.

44. The method of claim 43 , wherein the apoptosis inducing treatment is selected from a group consisting of radiation, hyperthermia, laser therapy, photodynamic therapy, chemotherapy, and cryosurgery.

45. The method of claim 43 , wherein the apoptosis inducing treatment is targeted therapy using an agent that targets the cancer.

46. The method of claim 43 , wherein the apoptosis is induced treatment with a chemotherapeutic agent selected from the group consisting of anthracyclines, antibiotics, alkylating agents, platinum-based agents, antimetabolites, topoisomerase inhibitors, and mitotic inhibitors.

47. The method of claim 43 , wherein the apoptosis inducing treatment is radiation therapy.

48. The method of claim 43 , further comprising, after administering the conjugate, treating the subject with a second apoptosis inducing treatment effective to induce expression of caspase.

49. The method of claim 48 , wherein the second apoptosis inducing treatment is the same as the first apoptosis inducing treatment.

50. The method of claim 48 , wherein the second apoptosis inducing treatment is different from the first apoptosis inducing treatment.