Early Use of Fostamatinib in Immune Thrombocytopenia.

INTRODUCTION: Fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, prevents antibody-mediated platelet destruction and has proven efficacy and safety in immune thrombocytopenia (ITP). However, evidence from real-world use in earlier treatment lines is limited. Here the objective was to evaluate the effectiveness and safety of fostamatinib as second- or third-line therapy in adult patients with ITP in Spain. METHODS: This multicenter study included 72 adult patients treated with fostamatinib across 22 Spanish centers, assessed retrospectively and prospectively. Demographic, clinical, and laboratory data, treatment responses, and adverse events (AEs) were analyzed. RESULTS: Median age was 67 years, and 55.6% of patients were women. The median time from ITP diagnosis to fostamatinib initiation was 17 months, and the baseline platelet count was 28 × 109/L. Bleeding manifestations were present in 26.4% of patients. Overall, 83.3% achieved a response and 65.3% a complete response. Response rates were 76.0% with second-line and 87.2% with third-line fostamatinib, with complete response rates of 56.0% and 70.2%, respectively. The median time to platelet response was 10.5 days, and the median time to peak platelet count was 62 days. Forty patients (55.5%) received fostamatinib as monotherapy. AEs occurred in 44.4% of patients, were predominantly grade 1-2, and most commonly consisted of diarrhea and hypertension. Treatment discontinuation due to insufficient effectiveness occurred in 27.8% of patients. CONCLUSION: Fostamatinib demonstrated high effectiveness and acceptable tolerability as second- or third-line therapy for adult ITP in real-world clinical practice.