Fostamatinib in chronic immune thrombocytopenia: a profile of its use in the USA.

Oral fostamatinib is an orally administered small molecule spleen tyrosine kinase (SYK) inhibitor approved for the treatment of adults with chronic immune thrombocytopenia (ITP) who have an inadequate response to a previous treatment. Fostamatinib has a unique mechanism of action, whereby its active metabolite targets the SYK-mediated pathway of platelet destruction. In clinical trials, fostamatinib provided durable responses in adults with chronic ITP who had not responded or had relapsed following treatment with one or more prior ITP therapies, including corticosteroids, thrombopoietin receptor agonists, rituximab, and/or splenectomy. Most patients who respond to fostamatinib maintain platelet counts of > 50 × 109/L for periods of ≥ 12 months. The most common adverse events reported with fostamatinib in clinical trials were diarrhea, hypertension, nausea, and increased transaminase levels.