Effectiveness, safety and persistence of filgotinib in rheumatoid arthritis with a specific focus on difficult-to-treat patients: results from a multicentre observational study

Filgotinib, a preferential JAK1 inhibitor, is among the most recently approved therapies for rheumatoid arthritis (RA). Real-world evidence remains limited, particularly for difficult-to-treat RA (D2T) patients, who are underrepresented in clinical trials. We therefore evaluated the efficacy, safety, and treatment persistence of filgotinib in a large cohort of patients with RA, with a specific focus on those with D2T RA. This retrospective multicentre study included patients with RA (ACR/EULAR 2010 criteria) treated with filgotinib across nine Italian centres. Patients were followed every 3–6 months for up to 3 years, with collection of clinical variables, laboratory data, and adverse events (AEs). A total of 254 patients were included (mean age 58 ± 12 years; 85% female), of whom 47% had D2T disease. Disease activity indices (CDAI, DAS28-CRP, PGA, PhGA) improved significantly from baseline ( p < 0.001), with remission rates reaching 41.3% (CDAI) and 70.5% (DAS28-CRP). Glucocorticoid (GC) use decreased from 64.4% to 32.6%. Improvements in disease activity and the GC-sparing effect were comparable between D2T RA and non-D2T RA patients. During follow-up, 153 AEs were reported, including 13 serious AEs and one infection-related death; non-serious infections were the most frequent events. Lipid profile remained stable throughout the study period, and two major cardiovascular events were reported. Treatment persistence was 88.4% at 6 months and 68% at 24 months, with no significant differences between D2T RA and non-D2T RA patients. Filgotinib demonstrated effective disease control, good safety and high treatment persistence in a real-world RA population, including a high proportion of D2T patients.