Vadastuximab talirine (SGN-CD33A) is an antibody-drug conjugate (ADC) targeting CD33, a transmembrane protein expressed on myeloid cells and overexpressed in acute myeloid leukemia (AML). It consists of a humanized anti-CD33 antibody linked to a cytotoxic DNA-crosslinking agent (pyrrolobenzodiazepine dimer). Upon binding to CD33, the ADC is internalized, releasing the payload to induce apoptosis in AML cells. It was investigated for the treatment of AML, but clinical development was discontinued due to safety concerns, including increased mortality in trials.