Filgotinib Safe, Effective for Rheumatoid Arthritis

Arthur Kavanaugh, MD

Filgotinib is safe and effective for patients with rheumatoid arthritis.

The findings were presented at the Congress of Clinical Rheumatology 2020 meeting.

Arthur Kavanaugh, MD, and a team of investigators evaluated the longer-term safety and tolerability of filgotinib for the treatment of rheumatoid arthritis. Further, they aimed to evaluate the long-term efficacy of filgotinib through the presentation of 156-week data from the DARWIN 3 long-term extension phase 2b study.

DARWIN 1 and 2 phase 2b studies evaluated filgotinib with and without methotrexate for 24 weeks in patients with moderate to severely active rheumatoid arthritis and inadequate response to methotrexate. Those who completed DARWIN 1 and 2 were eligible to participate in DARWIN 3.

Every patient in DARWIN 3 received filgotinib 200 mg/day aside for 14 males in the US who received 100 mg/day. The data cutoff was May 30, 2018 and exposure was calculated up to the cutoff date for those continuing the study at the time of analysis. The safety analysis included all safety data up to the cutoff date for those who received at least 1 dose of the study drug in DARWIN 3. Patients from DARWIN 1 were included in the filgotinib plus methotrexate group and those in DARWIN 2 were included in the filgotinib monotherapy group. The investigators calculated the event rate as total events/total patient-years of exposure to filgotinib.

A total of 739 patients enrolled in DARWIN 3, 497 from DARWIN 1 and 242 from DARWIN 2. A majority of the patients in 1 and 2 were female (81.5% and 81.8%) and white (75.3% and 74.8%) with a mean age of 53 and 52 years old.

At week 156, 59.9% of patients were continuing in the study. Common reasons for discontinuation were adverse events (26.5%) and patient request (9.1%). The total exposure to filgotinib was 2203 patient-years, mean ± standard deviation exposure was 3.04±1.22 for filgitonib plus methotrexate and 2.86±1.21 years for filgotinib monotherapy. The median time on the study drug was 3.5 years.

For the patients in DARWIN 3, the exposure-adjusted incidence rate (EAIR) for infections was 17.7 (95% CI, 15.9-19.4). EAIRs of infection were similar for patients with normal and decreased leukocyte counts. Among the patients, there were 330 infections in 622 patients with normal leukocytes and 50 infections in 116 patients with decreased leukocytes.

EAIRs for serious and herpes zoster infections were 1 (95% CI, .5-1.4) and 1.5 (95% CI, 1-2). Rates were similar for patients with normal and decreased leukocyte counts. There were small numbers of serious and herpes zoster infections. The team noted the need to further analyze the relationship between the onset of lymphopenia and herpes zoster infection across all filgotinib trials in rheumatoid arthritis.

Overall, no new safety signal emerged after 156 weeks of filgotinib treatment and efficacy was able to be sustained for some patients up through week 156 in both the monotherapy and methotrexate combination groups.

The study, "Rheumatoid Arthritis Treatment with Filgotinib: Week 156 Safety and Efficacy Data from a Phase 2b Open-Label Extension Study,” was published as part of the Congress of Clinical Rheumatology 2020 meeting.