OBJECTIVES: To evaluate the efficacy and safety of different doses of 
filgotinib, an oral Janus kinase 1 inhibitor, as monotherapy in patients with 
active rheumatoid arthritis (RA) and previous inadequate response to 
methotrexate (MTX).
METHODS: In this 24-week phase IIb study, patients with moderately to severely 
active RA were randomised (1:1:1:1) to receive 50, 100 or 200 mg filgotinib once 
daily, or placebo, after a ≥4-week washout from MTX. The primary end point was 
the percentage of patients achieving an American College of Rheumatology (ACR)20 
response at week 12.
RESULTS: Overall, 283 patients were randomised and treated. At week 12, 
significantly more patients receiving filgotinib at any dose achieved ACR20 
responses versus placebo (≥65% vs 29%, p<0.001). For other key end points at 
week 12 (ACR50, ACR70, ACR-N, Disease Activity Score based on 28 joints and C 
reactive protein, Clinical Disease Activity Index, Simplified Disease Activity 
Index and Health Assessment Questionnaire-Disability Index) significant 
differences from baseline in favour of filgotinib 100 and 200 mg versus placebo 
were seen; responses were maintained or improved through week 24. Rapid onset of 
action was observed for most efficacy end points. Dose-dependent increases in 
haemoglobin were observed. The percentage of patients with treatment-emergent 
adverse events (TEAE) was similar in the placebo and filgotinib groups (∼40%). 
Eight patients on filgotinib and one on placebo had a serious TEAE, and four 
patients, all of whom received filgotinib, experienced a serious infection. No 
tuberculosis or opportunistic infections were reported.
CONCLUSIONS: Over 24 weeks, filgotinib as monotherapy was efficacious in 
treating the signs and symptoms of active RA, with a rapid onset of action. 
Filgotinib was generally well tolerated.
TRIAL REGISTRATION NUMBER: NCT01894516.