TREATMENT OF CHRONIC AUTOIMMUNE THROMBOCYTOPENIC PURPURA WITH MONOCLONAL ANTI-D

Background: The platelet count increases transiently after treatment w ith polyclonal anti-D in about 50 percent of D+ patients with autoimmu ne thrombocytopenic purpura (AITP). The effect is usually attributed t o macrophage Fc-receptor blockade by antibody-coated red cells. As pol yclonal anti-D is in limited supply, prospective testing was performed on a monoclonal anti-D (MoAb D) in such patients. Study Design and Me thods: Seven D+ patients with chronic AITP received MoAb D intravenous ly at doses of 47 to 95 mu g per kg of body weight. Responses was asse ssed by studying platelet count increment. Hemolysis and red cell-boun d 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 p olyclonal anti-D, However, little or no platelet count increment was o bserved in six patients, while a transient response was observed in on ly one (platelet count 97 x 10(9)/L before MoAb D infusion and 163 x 1 0(9)/L 4 days later), Furthermore, because five patients showed signs of hemolysis and two became anemic, higher doses of MoAb D should be u sed only with caution in patients with AITP. Conclusion: The MoAb D us ed in this study cannot be proposed as an alternative treatment for pa tients with AITP.