SAN DIEGOThree multicenter phase II trials in the United States, Canada,
and Europe, representing the pivotal trials that led to approval of gemtuzumab
ozogamicin (Mylotarg), were updated at the 45th Annual Meeting of the American
Society of Hematology (abstract 615), looking only at patients age 60 and over.
Richard A. Larson, MD, professor of medicine, University of Chicago, presented
the results of the largest series of older patients with acute myeloid leukemia
(AML) in first relapse who have been treated with gemtuzumab.
Gemtuzumab is an antibody-targeted chemotherapy that has been FDA approved
for treatment of patients 60 years of age or older with CD33-positive AML in
first relapse who are not considered candidates for other cytotoxic therapy.
Dr. Larson said that 157 older AML patients in first relapse were entered
into the three phase II studies. Of the 157 patients, 66 (42%), were women and
91 (58%) were men. Their ages ranged from 60 to 87 (median, 68 years). Duration
of first remission was 2 to 74 months (median, 9.9 months). About half (52%) of
the patients had prior high-dose cytarabine consolidation therapy.
In these studies, gemtuzumab was administered intravenously at a dose of 9
mg/m2 on days 1 and 15. All 157 patients received the first dose,
119 received both doses, and 4 received a third dose.
Of the 157 study patients, 38 (24%) had a remission, characterized by 5% or
less leukemic blast cells in the bone marrow, hemoglobin of 9 g/dL or more,
absolute neutrophil count (ANC) of 1,500/µL or more, and red blood cell and
platelet transfusion independence.
Dr. Larson reported that 19 of these 38 responding patients had a complete
remission (CR) that included the above criteria plus recovery of platelets to
100,000/µL; another 19 patients had remission with incomplete platelet recovery