Recombinant humanized anti-IL-2 receptor antibody (daclizumab) produces responses in patients with moderate aplastic anemia

In contrast to severe aplastic anemia (sAA), the appropriate management of patients with moderate pancytopenia is unclear. In this study, we examined the efficacy of a humanized monoclonal antibody recognizing interleukin-2 receptor (daclizumab), which has proven to be a successful immunosuppressive agent in solid organ and bone marrow transplantation. We treated 17 patients with moderate aplastic anemia (mAA) with 1 mg/kg every 2 weeks for 3 months. mAA was defined as depression of 2 of the 3 blood counts: absolute neutrophil count 1200/mm(3) or less, platelet count 70 000/mm(3) or less, hemoglobin level 8.5 g/dL or lower, and absolute reticulocyte count 60 000/mm(3) or less. The primary end point of our protocol was a hematologic response in at least one affected peripheral blood value. Daclizumab had little toxicity. Six of the 16 (38%) evaluable patients responded to treatment. Two patients with previously chronic disease showed complete return of normal counts, which were sustained for more than 2 years following treatment. Four patients had single-lineage responses. Two previously transfusion-dependent patients became transfusion independent; one patient with many neutropenia-related infections had a normal neutrophil count following treatment. Daclizumab appears safe; its efficacy in this pilot protocol suggests that expanded study of this monoclonal antibody in immune-mediated bone marrow failure syndrome is warranted. (C) 2003 by The American Society of Hematology.