Safety and efficacy of filgotinib: Up to 4-year results from an open-label extension study of phase II rheumatoid arthritis programs

Objective. The long-term safety and efficacy of filgotinib (from phase II studies), with or without methotrexate (MTX), for the treatment of patients with rheumatoid arthritis was assessed in DARWIN 3, a long-term, open-label extension study (ClinicalTrials.gov: NCT02065700). Methods. Eligible patients completing the 24-week DARWIN 1 (filgotinib + MTX) and DARWIN 2 (filgotinib monotherapy) studies entered DARWIN 3, where they received filgotinib 200 mg/day, except for 15 men who received filgotinib 100 mg/day. Safety analyses were performed using the safety analysis set and the exposure-adjusted incidence rate (EAIR) of treatment-emergent adverse events (TEAEs) was calculated. Efficacy was assessed from baseline in the parent studies. Results. Of 790 patients completing the phase II parent studies, 739 enrolled in the study. Through April 2019, 59.5% of patients had received ≥ 4 years of the study drug. Mean (SD) exposure to filgotinib was 3.55 (1.57) years in the filgotinib + MTX group and 3.38 (1.59) years in the filgotinib monotherapy group. EAIR per 100 patient-years of exposure for TEAEs was 24.6 in the filgotinib + MTX group and 25.8 in the filgotinib monotherapy group, and for serious TEAEs, the EAIR was 3.1 and 4.3, respectively. American College of Rheumatology 20/50/70 responses among patients remaining in the study could be maintained through 4 years, with 89.3%/69.6%/49.1% of the filgotinib + MTX group and 91.8%/69.4%/44.4% of the monotherapy group maintaining ACR20/50/70 responses, respectively, based on observed data. Conclusion. Filgotinib was well tolerated with a 4-year safety profile comparable to that of the parent trials, both in patients receiving combination therapy with MTX or as monotherapy.