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Long-Term Fostamatinib Treatment of Adults with Immune Thrombocytopenia (ITP) during the Phase 3 Clinical Trial Program
Bussel JB, Arnold DM, Boxer MA, Cooper N, Mayer J, Zayed H, Tong S, Duliege AM
American journal of hematology. 2019
Abstract
Two randomized, double-blind, placebo-controlled studies demonstrated responses (≥50,000/muL) to fostamatinib in adults with long-standing immune thrombocytopenia (ITP). The long-term safety and efficacy of fostamatinib was evaluated in a follow-on, open-label-extension (OLE) study. Patients received double-blind fostamatinib in the randomized trials, and responders continued the same dose, 100-150mg BID, in the OLE. Non-responders received 100mg bid for 4 weeks and could escalate to 150mg bid at Week 4. Endpoints included stable response, platelet count ≥50,000/muL at 4/6 biweekly (randomized trials) or 2/3 monthly visits (OLE), and overall response, ≥1 platelet count ≥50,000/muL during Weeks 1-12. 146 patients received fostamatinib including 123 in the OLE. Median treatment duration was 6.7 months. Baseline median ITP duration was 8 years and median platelet count 16,000/muL; prior treatments included thrombopoietic agents (47%), splenectomy (35%), and rituximab (32%). Twenty-seven (18%) patients achieved a stable response, median duration >28 months, and median platelet count 89,000/muL. Sixty-four (44%) patients achieved an overall response (including stable responders) with median platelet count 63,000/muL and median response duration >28 months. 24/71 (34%) patients who had failed a thrombopoeitic agent achieved overall responses to fostamatinib. The most common AEs were diarrhea, hypertension, nausea, epistaxis and abnormal LFTs. Most AEs were mild/moderate and resolved or were managed with dose reduction, dose interruption, and/or secondary medication. Almost half of patients achieved an overall response, and most of these maintained their responses for >2 years. No new or increased frequency of AEs were seen at up to 31 months of treatment. This article is protected by copyright. All rights reserved.