ObjectiveTo evaluate the efficacy and safety of the Janus kinase-1-preferential inhibitor filgotinib versus placebo or tumour necrosis factor-α inhibitor therapy in patients with active rheumatoid arthritis (RA) despite ongoing treatment with methotrexate (MTX).MethodsThis 52-week, multicentre, double-blind, placebo-controlled and active-controlled phase III trial evaluated once-daily oral filgotinib in patients with RA randomised 3:3:2:3 to filgotinib 200 mg (FIL200) or filgotinib 100 mg (FIL100), subcutaneous adalimumab 40 mg biweekly, or placebo (through week 24), all with stable weekly background MTX. The primary endpoint was the proportion of patients achieving 20% improvement in American College of Rheumatology criteria (ACR20) at week 12. Additional efficacy outcomes were assessed sequentially. Safety was assessed from adverse events and laboratory abnormalities.ResultsThe proportion of patients (n=1755 randomised and treated) achieving ACR20 at week 12 was significantly higher for FIL200 (76.6%) and FIL100 (69.8%) versus placebo (49.9%; treatment difference (95% CI), 26.7% (20.6% to 32.8%) and 19.9% (13.6% to 26.2%), respectively; both pConclusionsFilgotinib improved RA signs and symptoms, improved physical function, inhibited radiographic progression and was well tolerated in patients with RA with inadequate response to MTX. FIL200 was non-inferior to adalimumab.Trial registration numberNCT02889796.