DC1 is an ADC cytotoxin, similar to the small groove-binding DNA alkylating agent CC-1065. DC1 can be used to synthesize antibody-drug conjugates targeted to the treatment of cancer. DC1Sme is a DC1 derivative with IC50 values of Ramos, Namalwa, HL60 / s and COLO 205 cancer cells of 22pm, 10pm, 32pm and 250pm, respectively.