Efficacy and safety of dapsone in adult primary immune thrombocytopenia.

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To assess efficacy and safety of dapsone in adult immune thrombocytopenia (ITP), a multicenter randomized controlled trial (RCT) and a real-word study cohort were performed. Participants were adults with primary ITP, transient response to corticosteroids ± intravenous immunoglobulin, and a platelet count ≤ 30x109/L (or ≤ 50x109/L with bleeding). Patients in the RCT were randomized in arm A (prednisone x3weeks+dapsone for 12 months) or arm B (prednisone alone). The observational study involved dapsone initiation at 100 mg/d with standard follow-up. The primary endpoint was the response rate (platelet count >30x109/L and ≥2×baseline) at 52 weeks, with the response rate at 24 weeks and adverse events as secondary endpoints. The RCT enrolled 93 patients (54.8% female), median age 48.5 years (46 in arm A, 47 in arm B). In the intention-to-treat analysis, 78.3% of patients in group A discontinued dapsone after a median of 4.6 weeks due to adverse events (66.7%) or lack of efficacy (33.3%). The response rate at week 52 was 21.7% (95% CI:10.9%-36.4%) in group A versus 8.5% (95% CI:2.7%-18.6%) in group B (p=0.17). The observational study, which was conducted after the end of the RCT, included 46 patients (52.2% female), median age 50.7 years. Adverse events occurred in 30.4%, leading to discontinuation of dapsone in 23.9%, and 13.6% (95% CI: 5.2%-27.4%) met the primary efficacy endpoint. Results from both studies showed an unfavorable risk-benefit ratio for the use of dapsone in adult primary ITP and suggest that, whenever available, second-line options should be used. NCT02627417, NCT02877706.