CD33 and acute myeloid leukemia: In May 2000, FDA approved the first ADC, gemtuzumab ozogamicin (Mylotarg), a humanized monoclonal antibody (gemtuzumab) conjugated with drug (ozogamicin) targeting CD33 protein, made by Wyeth for the treatment of patients with acute myeloid leukemia (AML) (30, 31).