An antibody-drug conjugate (ADC) containing a fully human monoclonal antibody directed against prostate-specific membrane antigen (PSMA), conjugated via a stable, enzyme-cleavable linker to monomethylauristatin E (MMAE), an auristatin derivative and a potent microtubule inhibitor, with potential antineoplastic activity. The monoclonal antibody moiety of this conjugate selectively binds to PSMA, a protein which is abundantly expressed on the surface of metastatic and hormone-refractory prostate cancer cells. Upon internalization and proteolytic cleavage, MMAE binds to tubulin and inhibits its polymerization, resulting in G2/M phase arrest and tumor cell apoptosis.