Safety and efficacy of fostamatinib in rheumatoid arthritis patients with an inadequate response to methotrexate in phase II OSKIRA-ASIA-1 and OSKIRA-ASIA-1X study

Abstract

Abstract Objective The primary objectives of two phase II studies of fostamatinib were to evaluate efficacy (OSKIRA-Asia-1: NCT01569074) and long-term safety/tolerability (OSKIRA-Asia-1X: NCT01640054) in patients from Asia with active RA despite MTX treatment. Methods OSKIRA-Asia-1 was a 12-week, multicentre, double-blind, placebo-controlled, parallel-group study. Patients were randomized to receive one of four fostamatinib doses (groups A–D; n = 31, 33, 33, 33) or placebo (group E; n = 33). OSKIRA-Asia-1X was a long-term extension study (100 mg fostamatinib qd) of patients who completed OSKIRA-Asia-1. RA signs and symptoms were measured by ACR response criteria and DAS based on a 28-joint count. Physical function status was assessed with the HAQ–Disability Index. Safety findings were monitored. Results In OSKIRA-Asia-1, fostamatinib revealed numerical improvements in ACR 20% response (ACR20) at week 12 in group A (100 mg bid) and group B (100 mg bid, then 150 mg qd) vs placebo. Statistically significant improvements in ACR20 and ACR50 at week 8 and in ACR70 at week 12, and statistically significant achievement in low disease activity (defined as DAS based on a 28-joint count ≤3.2 based on C-reactive protein) occurred in groups A and B. Improvement in physical function was numerically higher in group A. The most common adverse events were hypertension, diarrhoea and neutropenia. In OSKIRA-Asia-1X, the most common adverse events were nasopharyngitis, hypertension, RA and neutropenia. Conclusion Fostamatinib achieved both statistically and clinically significant improvements in RA signs and symptoms. The safety and tolerability of fostamatinib (plus MTX) were consistent with previous studies. Trial registration OSKIRA-Asia-1 trial registration: https://clinicaltrials.gov, NCT01569074; OSKIRA-Asia-1X trial registration: https://clinicaltrials.gov, NCT01640054.