Standard Administration and Fractionated Administration of Gemtuzumab Ozogamicin for Patients with Relapsed and Refractory Acute Myeloid Leukemia

Abstract 4342

(Purpose) We retrospectively analyzed the data regarding patients who received fractionated administration (FR) of gemtuzumab ozogamicin (GO) and standard administration (ST) of GO for the treatment of their refractory and relapsed acute myeloid leukemia in order to review the efficacy and safety of GO in each type of administration. (Method) The patients with relapsed and refractory acute myeloid leukemia (excluding patients with acute promyelocytic leukemia) who were treated with the ST of GO received 2 doses of monotherapy with 9 mg/m² GO as a 2-hour intravenous (iv) infusion with a 14–28-day interval. The fractionated GO group received 2 doses of GO monotherapy administered as a 2-hour iv infusion of 3 mg/(m²·day) on days 1, 3, and 5 with a 14–28-day interval. (Result) Eleven patients received ST and 9 received FR. The median age of all patients was 66.1 (55–77) years. Overall response rates (CR+CRp) in the ST and FR groups were 27% and 33%, respectively. The adverse events (grade 3–4) in the ST and FR groups were neutropenia (100% vs. 100%), thrombocytopenia (90.9% vs. 88.9%), and hypertransaminasis (18.2% vs. 0%). Grade 3–4 hypertransaminasis was seen only in the ST group. Infusion reactions occurred in 5 patients: 3 in the ST group and 2 in the FR group. The median CD33 positivity of blast cells of patients who received CR or CRp was 90.9% (78.2–99.5%). (Discussion) The response rates of the ST and FR groups were similar. However, the incidence of grade 3–4 hypertransaminasis tended to be higher in the ST group. These data suggest that FR of GO is less toxic than ST. Thus, FR of GO is safer than ST even for Japanese patients with acute myeloid leukemia.