Mease P, et al. - Given the implication of the Janus kinase 1 (JAK1) pathway in the pathogenesis of psoriatic arthritis, researchers assessed the effectiveness and safety of filgotinib, a selective JAK1 inhibitor, for its treatment. Outcomes of the EQUATOR trial, a randomized, double-blind, placebo-controlled phase 2 trial, indicate that filgotinib is effective for treating active psoriatic arthritis, with the emergence of no new safety signals.

Methods

• Adults (aged ≥18 years) from 25 sites in seven countries (Belgium, Bulgaria, Czech Republic, Estonia, Poland, Spain, and Ukraine) were enrolled in the EQUATOR trial.
• Included patients had active moderate-to-severe psoriatic arthritis (defined as at least five swollen joints and at least five tender joints) fulfilling classification for psoriatic arthritis (CASPAR) criteria, active or a documented history of plaque psoriasis, and an insufficient response or intolerance to at least one conventional synthetic disease-modifying anti-rheumatic drug (csDMARD).
• During the study, csDMARDs were continued in patients if they had received this treatment for at least 12 weeks before screening and were on a stable dose for at least 4 weeks before baseline.
• Random allocation of patients (1:1) to filgotinib 200 mg or placebo orally once daily for 16 weeks was made with an interactive web-based system (stratified by current use of csDMARDs and previous use of anti-tumor necrosis factor).
• Proportion of patients achieving 20% improvement in American College of Rheumatology response criteria (ACR20) at week 16 in the full analysis set (patients who received at least one dose of study drug) was assessed as the primary endpoint.
• Groups were compared regarding the primary endpoint with the Cochran-Mantel-Haenszel test and non-responder imputation method.

Results

• Researchers screened 191 patients between March 9, and September 27, 2017 and randomly allocated 131 to treatment (65 to filgotinib and 66 to placebo); study was completed by 60 (92%) patients in the filgotinib group and 64 (97%) patients in the placebo group.
• ACR20 was achieved in 52 (80%) of 65 patients in the filgotinib group and 22 (33%) of 66 in the placebo group at week 16 (treatment difference 47% [95% CI 30·2–59·6], p<0·0001).
• At least one treatment-emergent adverse event was noted in 37 (57%) patients who received filgotinib and 39 (59%) patients who received placebo.
• Grade 3 or worse event was noted in six participants.
• Nasopharyngitis and headache were the most common events; these occurred at similar proportions in each group.
• Each group displayed one serious treatment-emergent adverse event (pneumonia and hip fracture after a fall), one of which (pneumonia) was fatal in the filgotinib group.