An antibody-drug conjugate (ADC) consisting of the humanized monoclonal antibody Z4681A conjugated, via a cleavable disulfide linker, to the cytotoxic DNA alkylating agent DGN462, which is an indolino-benzodiazepine dimer containing a mono-imine moiety, with potential antineoplastic activity. The monoclonal antibody portion of anti-CD33 monoclonal antibody-DGN462 conjugate IMGN779 specifically binds to the cell surface antigen CD33 expressed on myeloid leukemia cells; upon internalization, the DGN462 moiety is released, and covalently binds to and alkylates DNA, thereby causing cell cycle arrest, apoptosis and inhibition of cell growth in myeloid leukemia cells that express CD33. CD33 is expressed on normal non-pluripotent hematopoietic stem cells and myeloid leukemia cells. Check foractive clinical trials using this agent.