Peficitinib, a JAK Inhibitor, in the Treatment of Moderate-to-severe Rheumatoid Arthritis in Methotrexate-inadequate Responders

Arthritis & Rheum 2016; ePub ahead of print

This Phase 2b study of peficitinib (ASP015K), an orally administered once-daily JAK inhibitor, plus MTX, demonstrated efficacy across multiple secondary endpoints with higher peficitinib doses. Peficitinib in combination with MTX was well tolerated with a safety profile that was consistent with previous studies.A high placebo response rate was seen in both Latin and North America, when patient data were stratified. This high placebo rate is problematic for the accurate interpretation of peficitinib efficacy in this trial. However, in the patients in Europe, statistically significant differences in the percentage of patients achieving ACR20 responses at Week 12 were seen in the peficitinib 100 mg and 150 mg groups Overall, a greater percentage of patients in all peficitinib treatment groups achieved ACR20, 50, and 70 versus placebo, though no peficitinib treatment group reached statistical significance for ACR50 or ACR70 response rate versus placebo at Week 12.In contrast to the two previous Phase 2b studies with peficitinib, no dose-dependent ACR20 response was observed, although analysis of DAS28 and the inflammatory markers, CRP and ESR, did suggest a dose-dependent response in the overall population.Peficitinib in combination with MTX was well tolerated at all dose levels with a safety profile that was consistent with previous studies.