An antibody-drug conjugate (ADC) composed of a humanized monoclonal antibody directed against the six transmembrane epithelial antigen of the prostate 1 (STEAP1), and conjugated, via a protease-cleavable peptide linker, to monomethyl auristatin E (MMAE), an auristatin derivative and a potent microtubule disrupting agent, with potential antineoplastic activity. Upon administration of vandortuzumab vedotin, the monoclonal antibody moiety of vandortuzumab vedotin binds to STEAP1-expressing tumor cells and is internalized, thereby delivering MMAE intracellularly. Proteolytic cleavage releases MMAE, which then binds to tubulin and inhibits its polymerization, resulting in G2/M phase arrest and tumor cell apoptosis. STEAP1, a tumor-associated antigen (TAA), is overexpressed in a variety of cancer cell types.