An antibody-drug conjugate (ADC) composed of anvatabart, a monoclonal antibody targeting human epidermal growth factor receptor 2 (EGFR2; HER2) site-specifically conjugated at two engineered residues of para-acetyl-phenylalanine (pAcF) via a stable oxime linker to the monomethyl auristatin F (MMAF) analog and potent microtubule inhibitor opadotin, with potential antineoplastic activity. Upon administration of anvatabart opadotin, the antibody moiety targets and binds to HER2 on tumor cells. Upon antibody/antigen binding and internalization, opadotin binds to and inhibits tubulin polymerization, which results in G2/M phase arrest and tumor cell apoptosis. HER2, a tyrosine kinase receptor, is overexpressed by many cancer cell types. The site-specific conjugation of the cytotoxic agent to the antibody improves the biophysical properties of anvatabart opadotin, increases payload stability and optimizes its efficacy.