Treatment of chronic autoimmune thrombocytopenic purpura with monoclonal anti‐D

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Abstract
Background: The platelet count increases transiently after treatment with polyclonal anti‐D in about 50 percent of D+ patients with autoimmune thrombocytopenic purpura (AITP). The effect is usually attributed to macrophage Fc‐receptor blockade by antibody‐coated red cells. As polyclonal anti‐D is in limited supply, prospective testing was performed on a monoclonal anti‐D (MoAb D) in such patients.Study Design and Methods: Seven D+ patients with chronic AITP received MoAb D intravenously at doses of 47 to 95 μg per kg of body weight. Response was assessed by studying platelet count increment. Hemolysis and red cell‐bound MoAb D were measured before and after MoAb D administration.Results: MoAb D red cell binding was demonstrated in all patients at a ratio higher than that observed in AITP patients successfully treated with polyclonal anti‐D. However, little or no platelet count increment was observed in six patients, while a transient response was observed in only one (platelet count 97 × 109/L before MoAb D infusion and 163 × 109/L 4 days later). Furthermore, because five patients showed signs of hemolysis and two became anemic, higher doses of MoAb D should be used only with caution in patients with AITP.Conclusion: The MoAb D used in this study cannot be proposed as an alternative treatment for patients with AITP.