Gemtuzumab ozogamicin: promise and challenge in patients with acute myeloid leukemia.

CD33 is a suitable target to guide delivery of a toxic moiety to most acute myeloid leukemia cells. Gemtuzumab ozogamicin (Mylotarg) is a humanized antiCD33 monoclonal antibody covalently linked to a derivative of a cytotoxic antibiotic, calicheamicin. As a single agent, gemtuzumab ozogamicin has activity (complete remission rate of 15-20%) in patients with relapsed disease. Gemtuzumab ozogamicin-based combinations are being studied as induction, maintenance and relapse regimens. The chemical hepatotoxicity often observed with gemtuzumab ozogamicin therapy is of little clinical consequence. However, hepatic veno-occlusive disease is a relatively frequent and serious toxicity for which no clear risk factors, other than stem cell transplantation, have been defined. Gemtuzumab ozogamicin-based regimens may be particularly worthy of study in patients with acute promyelocytic leukemia. Gemtuzumab ozogamicin is approved as single-agent therapy for patients over the age of 60 years in first relapse who are not considered candidates for cytotoxic therapy. The administration of gemtuzumab ozogamicin should be carried out under a level of supervision commensurate with that afforded other intensely myelosuppressive agents. Gemtuzumab ozogamicin-based combinations should not be prescribed outside the research setting until further data is available.