Long-Term Safety, Efficacy, and Patient-Centered Outcomes of Filgotinib in the Treatment of Rheumatoid Arthritis: Current Perspectives

Filgotinib is an orally administered, preferential Janus kinase (JAK) inhibitor indicated for the treatment of moderate-to-severe rheumatoid arthritis (RA). The short-term safety, efficacy, and patient-reported outcomes (PROs) with filgotinib from Phase 2b/3 clinical trials (DARWIN 1 and 2; FINCH 1, 2, and 3) are described in patients who inadequately responded to methotrexate (MTX) and biologic disease-modifying antirheumatic drugs or who were naïve to MTX. This article reviews the safety and efficacy from the long-term extension (LTE) trials, DARWIN 3 (N=739) and FINCH 4 (N=2731), and PROs across the filgotinib development program in RA. Overall, in the DARWIN clinical trials (conducted from 2013–2023), patients received their LTE treatment for ≤8 years, while in the FINCH trials (ongoing from 2016–2025), patients received filgotinib treatment for ≤6 years in the LTE. The longer-term safety profile and consistent, sustained efficacy (American College of Rheumatology 20/50/70, Clinical Disease Activity Index, and Disease Activity Scale in 28 joints with C-reactive protein response rates) of filgotinib were largely similar to those observed in the shorter-term parent trials ≤52 weeks. PRO results from the parent trials showed improvements in patients’ quality of life with filgotinib treatment, which compared to or exceeded improvements seen with placebo and active comparators (adalimumab, MTX). Filgotinib has a higher specificity for JAK1 compared with other therapeutic treatments, leading to reduced inhibition of JAK2/3–dependent pathways, potentially providing a distinct safety profile. Filgotinib is approved in Europe and Japan for treatment of people with moderate-to-severe RA, though it has not been approved by the US Food and Drug Administration, due to concerns around the benefit/risk profile of the filgotinib 200-mg dosage and the potential impact on semen parameters.