Brief communication: Successful treatment of pure red-cell aplasia with an anti-interleukin-2 receptor antibody (daclizumab)

Abstract

Background: Pure red-cell aplasia (PRCA) is a rare hematologic disease characterized by anemia, reticulocytopenia, and absence of bone marrow erythroid precursors. Most patients respond to some form of immunosuppressive treatment, but few prospective clinical trials have been performed.

Objective: To examine the efficacy of a humanized monoclonal antibody to the interleukin-2 receptor (daclizumab) for treating PRCA.

Design: Pilot study.

Setting: Federal government research hospital.

Patients: 15 patients with idiopathic PRCA.

Intervention: Daclizumab, 1 mg/kg of body weight, every 2 weeks for a total of 5 infusions. Pure red-cell aplasia was defined as transfusion-dependent anemia with a reticulocyte count of 60 x 10(9) cells/L or less and bone marrow showing absent or diminished erythroid precursors.

Measurements: Response to therapy was assessed by transfusion independence, increments in reticulocyte count, and nontransfused hemoglobin.

Results: Daclizumab had little toxicity. Of the 15 patients, 6 patients (40%) responded to treatment. All responders became transfusion-independent and achieved normal or near-normal hemoglobin values and normal reticulocyte counts.

Limitations: The study was unblinded, and the number of patients was too small to assess drug safety reliably.

Conclusions: Daclizumab seems safe. Its efficacy in this pilot protocol suggests that expanded study in PRCA and other bone marrow failure syndromes is warranted.