Patent ID: 7638528

Claim:
A compound having the structure of Formula V: wherein, R 31 is (C 1 -C 16 ) alkyl, branched alkyl, alkenyl or alkynyl; R 32 is (C 1 -C 16 ) alkyl, branched alkyl, alkenyl or alkynyl; X 31 is O, S, or NHC═O; X 32 is O, S, or NHC═O; X 33 is O, S, or amino; R 33 is an therapeutic agent selected from the group consisting of doxorubicin, idarubicin, epirubicin, daunorubicin, mitomycin, SN-38, camptothecin, topotecan, 9-nitrocamptothecin, and 9-aminocamptothecin, mitoxanthrone, methotrexate, and CPT-11 and is covalently linked via an ester, amido, or carbamate linkage to the S, O or amino group of X 33 .