Brief Communication: Successful Treatment of Pure Red-Cell Aplasia with an Anti–Interleukin-2 Receptor Antibody (Daclizumab)

7 February 2006 | Volume 144 Issue 3 | Pages 181-185

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 10⁹ 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.

Editors' Notes Context Pure red-cell aplasia (PRCA) seems to have an autoimmune pathophysiology. Currently available treatments are relatively toxic. Daclizumab is a genetically engineered human IgG1 that blocks the interleukin-2 receptor necessary for clonal expansion of activated T cells. Contribution Fifteen patients with PRCA were treated with daclizumab. Forty percent achieved normal hemoglobin levels within 18 months of starting therapy. The drug produced little toxicity other than minor skin rash. Implications Daclizumab may provide a nontoxic alternative for treating a severe, relatively refractory cause of anemia. Cautions This is a small, unblinded study. —The Editors

 

Author and Article Information

From National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland.

Acknowledgments: The authors thank Colin Wu, who provided statistical expertise and helped develop stopping rules for the study, and Barbara Weinstein, who screened and recruited patients and managed the data for the study.

Grant Support: No outside funding was received for this study.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Elaine M. Sloand, MD, Hematology Branch, National Heart, Lung, and Blood Institute, 9000 Rockville Pike, Building 10 CRC 4E5230, Bethesda, MD 20892; e-mail, sloande{at}nih.gov.

Current Author Addresses: Dr. Sloand: Hematology Branch, National Heart, Lung, and Blood Institute, 9000 Rockville Pike, Building 10 CRC 4E5230, Bethesda, MD 20892.

Drs. Scheinberg and Young: Hematology Branch, National Heart, Lung, and Blood Institute, 9000 Rockville Pike, Building 10 CRC 3E, 3-5142, Bethesda, MD 20892.

Dr. Maciejewski: Cleveland Clinic Foundation, Taussig Cancer Center, 9500 Euclid Avenue, Cleveland, OH 22195.

Author Contributions: Conception and design: E.M. Sloand, J. Maciejewski, N.S. Young.

Analysis and interpretation of the data: E.M. Sloand, J. Maciejewski, N.S. Young.

Drafting of the article: E.M. Sloand, J. Maciejewski, N.S. Young.

Critical revision of the article for important intellectual content: E.M. Sloand, N.S. Young.

Final approval of the article: E.M. Sloand, J. Maciejewski, N.S. Young.

Provision of study materials or patients: E.M. Sloand, P. Scheinberg, J. Maciejewski, N.S. Young.

Obtaining of funding: N.S. Young.

Administrative, technical, or logistic support: E.M. Sloand, N.S. Young.

Collection and assembly of data: E.M. Sloand.