Sustained response off therapy after fostamatinib: A chronic refractory ITP case report.

Fostamatinib is a SYK-inhibitor drug recently approved by the FDA and EMA for treating chronic immune thrombocytopenia. This drug induces a response in about 40% of patients and has a good toxicity profile. It is known that discontinuing thrombopoietin receptor agonists (TRAs) with the maintenance of sustained response off therapy is possible. On fostamatinib, we do not yet have such information. In this case report, we describe the story of a woman with a multirefractory immune thrombocytopenia (steroids, splenectomy, rituximab, both available TRAs). After 16 years from diagnosis, she started fostamatinib therapy within a clinical trial and achieved a complete response. Grade 1-2 headache and diarrhea occurred during the first months of therapy. These adverse events were resolved with dose reduction of fostamatinib. Despite the dose reduction, the platelet count remained steadily above 80 × 109 /L. After 4 years, fostamatinib was gradually reduced and finally discontinued with no drop in platelet count. This is the first case in which fostamatinib discontinuation resulted in a sustained response off therapy.