Efficacy and safety of gemtuzumab ozogamicin in patients with CD33-positive acute myeloid leukaemia in first relapse.

Gemtuzumab ozogamicin (CMA-676, Mylotarg, an antibody-targeted chemotherapy agent, was recently approved by the FDA for the treatment of patients with CD33+ acute myeloid leukaemia (AML) in first relapse who are 60 years of age or older and who are not considered candidates for other types of cytotoxic chemotherapy. In combined Phase II studies of 142 patients with CD33+ AML in first relapse, gemtuzumab ozogamicin monotherapy was associated with a 30% overall response rate. While treated patients had relatively high incidences of myelosuppression, grade 3 or grade 4 hyperbilirubinaemia (23%) and elevated hepatic transaminases (17%), the incidences of grade 3 or grade 4 mucositis (4%) and infections (28%) were low compared with what might be expected in association with conventional chemotherapeutic treatment. In contrast with the usual in-patient administration of cytarabine and anthracycline-containing induction regimens, a large number of patients were treated with gemtuzumab ozogamicin as outpatients (38% and 41% for the first and second doses, respectively). Two prognostic factors for patients with AML in first relapse, age and duration of complete remission, had relatively little effect on response rates to gemtuzumab ozogamicin. Preliminary data in pediatric patients also suggest the immunoconjugate to be reasonably well tolerated. Studies of gemtuzumab ozogamicin in combination with anthracycline and cytarabine are underway. Gemtuzumab ozogamicin, administered to patients with CD33+ AML in first relapse, has shown overall response rates comparable to conventional agents and a safety profile that appears to be favourable.