An antibody-drug conjugate (ADC) composed of a monoclonal antibody directed against the oncofetal antigen 5T4 conjugated to the auristatin derivative and microtubule-disrupting cytotoxic agent monomethyl auristatin E (MMAE), with potential antineoplastic activity. Upon administration of anti-5T4/MMAE ADC XB010, the anti-5T4 antibody moiety selectively binds to tumor cells expressing 5T4. Upon binding and internalization, MMAE binds to tubulin and inhibits its polymerization, which results in G2/M phase arrest and induces apoptosis in 5T4-expressing tumor cells. 5T4, a transmembrane glycoprotein, is overexpressed by a variety of cancer cell types while its expression is limited in normal adult tissues; its expression is correlated with increased invasiveness.