Treatment with fostamatinib in patients with immune thrombocytopenia: Experience from the Andalusian region in Spain-The Fostasur Study

Immune thrombocytopenia (ITP) is characterized by low platelet counts (PLTs) and an increased risk of bleeding. Fostamatinib, a spleen tyrosine kinase inhibitor, has been approved as a second-line treatment for ITP. Real-world data on fostamatinib are lacking. This observational, retrospective, multicentre study, conducted in the Andalusia region of Spain, evaluated 44 adult primary ITP patients (47.7% female; median age 58 years; newly diagnosed ITP 6.8%; persistent 13.6%; chronic 79.5%; median four prior treatments) after >= 4 weeks of fostamatinib therapy. The median PLT at the initiation of fostamatinib was 15 x 109/L. Common reasons for starting fostamatinib were refractoriness or intolerance to prior therapy, oral medication preference, history of thrombosis and cardiovascular risk. Dosing was individualized based on efficacy and tolerance. After 2 weeks, global response rate was 56.8% (response and complete response). Response rates were 70.5%, 62.5% and 64% at 4 weeks, 12 weeks and at the end of the study respectively. Adverse events were mild, and no patients discontinued as a result. This real-world study demonstrated a response rate similar to fostamatinib as seen in the pivotal clinical trials while including newly diagnosed patients and allowing for individualized dosing. Patients with immune thrombocytopenia (ITP) have low platelet counts (PLTs) and are at an increased risk of bleeding events. In this observational, retrospective study, we provide real-world data on the use of fostamatinib, a spleen tyrosine kinase inhibitor, in treating ITP at multiple centres in the Andalusia region of Spain. This study included 44 adult primary ITP patients (47.7% female, median age 58 years) that ranged from newly diagnosed to chronic disease with a median of four prior ITP therapies. The dose of fostamatinib was individualized based on effectiveness and adverse events (AEs). PLTs were measured at diagnosis, baseline, 2, 4 and 12 weeks of fostamatinib therapy, and at the end of the study. After treatment, 56.8%-70.5% of the ITP patients responded to fostamatinib and PLT increased from a median of 15 x 109/L at baseline to 162 x 109/L at 12 weeks. AEs associated with fostamatinib were generally mild and did not result in the discontinuation of therapy. The results of this real-world study were similar to those seen in the phase 3 clinical trials and other real-world data. Importantly, this study included newly diagnosed ITP patients and allowed for individualized dosing.image