Efficacy and Safety of Selective JAK 1 Inhibitor Filgotinib in Active Rheumatoid Arthritis Patients With Inadequate Response to Methotrexate

The administration of Janus kinase (JAK) inhibitors as well as biological disease-modifying anti-rheumatic drugs has dramatically improved even the clinical outcomes in rheumatoid arthritis (RA) patients with inadequate response to methotrexate (MTX). The dysregulation of JAK-signal transducer and activator of transcription (STAT) pathways via overproduction of cytokines, such as interleukin-6 (IL-6) is involved in the pathogenesis of RA. Filgotinib is a selective JAK1 inhibitor to be approved for use in RA. Filgotinib is effective in suppressing disease activity and preventing the progression of joint destruction due to inhibition of the JAK-STAT pathway. IL-6 inhibitors such as tocilizumab also inhibit the JAK-STAT pathways due to inhibition of IL-6 signaling. We will evaluate whether the effectiveness and safety of filgotinib monotherapy is non-inferior to those of tocilizumab monotherapy in RA patients with inadequate response to MTX.