An immunoconjugate that consists of a humanized monoclonal antibody (MLN591), directed against prostate-specific membrane antigen linked to a maytansinoid (DM1). The monoclonal antibody moiety of MLN2704 binds to tumor cells expressing prostate-specific membrane antigen; MLN274 is then internalized into the tumor cell where the DM1 maytansinoid moiety binds to tubulin and inhibits tubulin polymerization and microtubule assembly, resulting in a disruption of microtubule activity and cell division, and cell death. orA substance that is being studied in the treatment of prostate cancer. It belongs to the family of drugs called antibody drug conjugates. Also called MLN591DM1.