A drug used to treat acute myeloid leukemia (AML) that is CD33 positive (expresses the protein CD33). It is used in patients whose disease is newly diagnosed. It is also used in patients aged 2 years or older whose disease has not gotten better with other treatment or has recurred (come back). Gemtuzumab ozogamicin contains a monoclonal antibody that binds to CD33, which is found on some leukemia cells. It also contains a toxic substance, which may help kill cancer cells. Gemtuzumab ozogamicin is a type of antibody-drug conjugate. Also called Mylotarg.