Patent ID: 8802632

Claim:
A method for treating a cancer in a subject suffering from such cancer, comprising administering to the subject a therapeutically effective amount of a compound having a structure represented by formula (II), or a conjugate thereof with a ligand that is an antibody, wherein n is 0, 1, or 2; R 1 , R 2 and R 3 are independently H, unsubstituted or substituted C 1 -C 10 alkyl, unsubstituted or substituted C 2 -C 10 alkenyl, unsubstituted or substituted C 2 -C 10 alkynyl, unsubstituted or substituted aryl, unsubstituted or substituted heteroaryl, unsubstituted or substituted (CH 2 ) 1-2 O(C 1 -C 10 alkyl), unsubstituted or substituted (CH 2 ) 1-2 O(C 2 -C 10 alkenyl), unsubstituted or substituted (CH 2 ) 1-2 O(C 2 -C 10 alkynyl), (CH 2 ) 1-2 OC(═O)(C 1 -C 10 alkyl), unsubstituted or substituted (CH 2 ) 1-2 OC(═O)(C 2 -C 10 alkenyl), unsubstituted or substituted (CH 2 ) 1-2 OC(═O)(C 2 -C 10 alkynyl), unsubstituted or substituted C(═O)(C 1 -C 10 alkyl), unsubstituted or substituted C(═O)(C 2 -C 10 alkenyl), unsubstituted or substituted C(═O)(C 2 -C 10 alkynyl), unsubstituted or substituted cycloaliphatic, unsubstituted or substituted heterocycloaliphatic, unsubstituted or substituted arylalkyl, or unsubstituted or substituted alkylaryl; R 4 is R 5 is H, C 1 -C 5 alkyl, C 2 -C 5 alkenyl, C 2 -C 5 alkynyl, CO(C 1 -C 5 alkyl), CO(C 2 -C 5 alkenyl), or CO(C 2 -C 5 alkynyl); or a pharmaceutically acceptable ester thereof, a pharmaceutically acceptable amide thereof at the carboxyl group of R 4 with the α-amino group of an α-amino acid, or a pharmaceutically acceptable salt thereof.