Activity of alemtuzumab in patients with CD52-positive acute leukemia

BACKGROUND. Alemtuzumab is a humanized monoclonal antibody directed against the cell surface antigen CD52 and has demonstrated activity in chronic lymphocytic leukemia and other CD52-positive lymphoproliferative disorders. Because CD52 also is expressed on acute leukemic blasts, the authors investigated the safety and efficacy of alemtuzumab in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). METHODS. Fifteen patients with CD52-positive (≥20%), recurrent or refractory acute leukemia (9 patients with AML and 6 patients with ALL) received alemtuzumab at a dose of 30 mg intravenously given 3 times a week (dose escalation during Week 1) for a total of 4 to 12 weeks. RESULTS. The median age of the patients was 39 years (range, 18-71 years). Patients had received a median of 3 prior therapies (range, 1-5 prior therapies). Two patients (13%) achieved a bone marrow complete response and 1 patient achieved a substantial reduction in bone marrow blasts. No complete remissions were observed. Ten patients developed disease progression while on study. Alemtuzumab was myelosuppressive in nearly all patients. Infusion-related toxicities were common, but usually did not exceed Grade 2 (according to the National Cancer Institute Common Toxicity Criteria). Infectious episodes occurred in 13 patients (87%) and included pneumonia (6 patients), bacteremia (11 patients), fungemia (2 patients), and cytomegalovirus reactivation (2 patients). CONCLUSIONS. Single-agent alemtuzumab was found to have limited activity in recurrent or refractory acute leukemia. An evaluation in patients with a better prognosis, in combination with other agents or as part of consolidation therapy, is warranted.