CD33 and acute myeloid leukemia: GO was granted accelerated approval by the United States (US) Food and Drug Administration (FDA) in 2000 as monotherapy (9 mg/m2 repeated after 14 days on approximately 28-day cycles) for patients ≥ 60 years of age with CD33-positive (CD33 +) acute myeloid leukemia (AML) in first relapse and who were not candidates for standard chemotherapy [4].