Two-Year Safety and Effectiveness of Peficitinib in Moderate-To-Severe Rheumatoid Arthritis: A Phase IIb, Open-Label Extension Study

Abstract Introduction Peficitinib is a novel orally bioavailable, once-daily Janus kinase (JAK) inhibitor approved in Japan for the treatment of rheumatoid arthritis (RA). This 2-year extension study of two global phase IIb trials investigated the long-term safety and effectiveness of peficitinib. Methods All eligible patients with moderate-to-severe RA including patients in the placebo group who participated in one of two global phase IIb trials (‘with methotrexate’ or ‘without methotrexate’) were included in this 2-year open-label extension study and were converted to peficitinib 100 mg once daily. The primary objective was to evaluate an additional 2 years of safety by assessing treatment-emergent adverse events (AEs) and clinical laboratory evaluations for 105 weeks. Evaluation of an additional 2 years of effectiveness using American College of Rheumatology (ACR) 20/50/70 responses was the exploratory objective. Results Overall, 611 patients were enrolled in the extension study: 319 (52.2%) patients completed the study and 292 (48%) discontinued treatment, including for withdrawal of patient consent (n = 96), failure to achieve low disease activity (n = 62), and AE not including death (n = 41). AEs were reported in 463 (76%) patients. The most common AEs (per 100 patient-years) were upper respiratory tract infections (9.9) and urinary tract infections (7.2). Serious AEs were reported in 80 (13%) patients, with incidences per 100 patient-years of serious infections 2.7, herpes zoster 1.5 (including one herpes zoster ophthalmic), and malignancies 0.6 (most frequently basal cell carcinoma). At week 105, 269 (44%) patients demonstrated an ACR20 response relative to their respective phase IIb trial baselines. Conclusion Among 319 patients who completed this 2-year extension of two global phase IIb studies, peficitinib 100 mg once daily demonstrated a stable safety profile and sustained effectiveness in patients with moderate-to-severe RA. Trial Registration ClinicalTrials.gov identifier, NCT01711814. Registered 19 October 2012. Funding Astellas Pharma Global Development, Inc.