An antibody-drug conjugate (ADC) composed of a humanized antibody targeting integrin beta-6 and conjugated to the microtubule-disrupting cytotoxic agent monomethyl auristatin E (MMAE), with potential antineoplastic activity. Upon administration, the antibody moiety of anti-integrin beta-6/MMAE ADC SGN-B6A targets and binds to integrin beta-6 on the surface of tumor cells. Following internalization of SGN-B6A and release of MMAE, MMAE targets and binds to tubulin, and inhibits microtubule polymerization. This results in G2/M phase cell cycle arrest and apoptosis in integrin beta-6-expressing tumor cells. Integrin beta-6 is a subunit of integrin alpha-V beta-6 (aVb6). Integrin aVb6, a cell adhesion and signaling receptor, is upregulated in certain cancer cell types and has been associated with increased proliferation, migration and invasion of tumor cells.