Filgotinib may have demonstrated sustained safety and efficacy over an extended period in patients with rheumatoid arthritis, according to the final results from the long-term extension study of the DARWIN 3 trial.
In the study, published in RMD Open, researchers reinforced filgotinib’s role as a promising long-term treatment option. The DARWIN 3 study involved 739 patients who had previously completed the DARWIN 1 and DARWIN 2 trials, which assessed the safety and efficacy of filgotinib in combination with methotrexate and as a monotherapy, respectively. Participants in the long-term extension phase of the study were given filgotinib at a daily dose of 200 mg, with a subset of male participants receiving 100 mg daily. The primary endpoints of the study were safety, tolerability, and treatment-emergent adverse events (TEAEs), with additional measures evaluating efficacy.
The long-term safety analysis showed that filgotinib was well tolerated, with an average exposure of 259.8 weeks (3,706.3 patient-years). Despite 67.3% of patients discontinuing treatment prematurely (as a result of TEAEs or voluntary withdrawals), the overall safety profile remained manageable. The incidence rate of TEAEs was 67 per 100 patient-years, with serious TEAEs at 3.8 per 100 patient-years. Infections were the most common adverse events, with an incidence rate of 23.3 per 100 patient-years. The rates for serious infections and herpes zoster were 1.3 per 100 patient-years.
Notably, serious adverse cardiovascular events occurred at a low rate of 0.19 per 100 patient-years, and malignancies were reported at 0.6 per 100 patient-years.
Filgotinib continued to show therapeutic effects, though disease response plateaued at 12 weeks and declined slowly thereafter. Using the American College of Rheumatology (ACR) criteria, the researchers reported ACR20, ACR50, and ACR70 response rates of 26.9%, 20.2%, and 14.7%, respectively, at week 396. Despite the gradual decline, filgotinib provided significant long-term benefits. The results supported filgotinib as a reliable and safe option for long-term rheumatoid arthritis (RA) management.
"Long-term treatment with filgotinib was well tolerated, with no new safety signals identified vs previous studies," said lead study author Rene Westhovens, of the Department of Development and Regeneration at the Skeletal Biology and Engineering Research Center, Katholieke Universiteit in Belgium, and colleagues.
The study’s findings underscored the importance of ongoing monitoring of long-term drug effects. Filgotinib’s low rates of serious adverse events and sustained efficacy may provide clinicians with a valuable therapeutic tool for managing chronic RA.
No conflicts of interest were mentioned in the study.
