LONG-TERM SAFETY PROFILE OF THE ORAL SPLEEN TYROSINE KINASE INHIBITOR FOSTAMATINIB IN IMMUNE THROMBOCYTOPENIA (ITP) AND OTHER DISEASES

Abstract

Introduction: Fostamatinib is an oral, potent inhibitor of spleen tyrosine kinase (SYK) with proven efficacy and a manageable safety profile for the treatment of ITP. Long-term safety data on fostamatinib at various dosing regimens (up to 150 mg BID) has been collected in >4000 patients with ITP, rheumatoid arthritis (RA), and other autoimmune, allergic and neoplastic disorders. The safety and tolerability of fostamatinib were consistent across different patient populations We present a summary analysis of the fostamatinib safety data from the ITP and RA studies. Methods: Fostamatinib safety data from 2 randomized, double-blind, placebo-controlled, phase 3 studies and the long-term, open-label, extension (OLE) study in ITP were pooled and are based on a starting dose of 200 mg/day, which was increased to 300 mg/day after 4 weeks in 88% of patients. Fostamatinib safety data from 13 phase 2/3 studies in RA were pooled and are based on a dosing regimen of 100-150 mg/day (n = 1232) or 200-300 mg/day (n = 2205). Results: The pooled data set for ITP included 146 patients. The mean duration of fostamatinib treatment was 19 months (range 4000 patients across different disease populations. Fostamatinib has a consistent and manageable safety profile. No new safety signals and no cumulative toxicity were observed with up to 81 months (6.8 years) of continuous treatment.