Prospective Phase 1/2 Study of Rituximab in Childhood and Adolescent Chronic Immune Thrombocytopenic Purpura

We assessed safety and efficacy of rituximab in a prospective study of 36 patients, age 2.6 to 18.3 years, with severe chronic immune thrombocytopenic purpura (ITP). The primary outcome of sustained platelets above 50 x 10(9)/L (50,000/mm3) during 4 consecutive weeks, starting in weeks 9 to 12, was achieved by 11 of 36 patients (31%, confidence interval [CI], 16% to 48%). Median response time was 1 week (range, 1 to 7 weeks). Attainment of the primary outcome was not associated with age, prior pharmacologic responses, prior splenectomy, ITP duration, screening platelet count, refractoriness, or IgM reduction. First-dose, infusion-related toxicity was common (47%) despite premedication. Significant drug-related toxicities included third-dose hypotension (n = 1) and serum sickness (n = 2). Peripheral B cells were depleted in all subjects. IgM decreased 3.4% per week, but IgG did not significantly decrease. Rituximab was well tolerated, with manageable infusion-related side effects, but 6% of subjects developed serum sickness. Rituximab is beneficial for some pediatric patients with severe, chronic ITP.