CD33’s validity as a therapeutic target in AML was exemplified by gemtuzumab ozogamicin—an antibody–drug conjugate (ADC) directed against CD33—which, in combination with daunorubicin and cytarabine, was approved by both the US FDA and the EMA for the treatment of newly diagnosed CD33-positive AML [20–23]. This evidence concerns the gene CD33 and acute myeloid leukemia.