Sustained resolution of enthesitis and peripheral arthritis over 104 weeks with bimekizumab in axial spondyloarthritis.

BACKGROUND: Bimekizumab (BKZ), a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F in addition to IL-17A, has demonstrated 2-year efficacy in non-radiographic axial spondyloarthritis (nr-axSpA) and radiographic axSpA (r-axSpA) phase III studies. OBJECTIVE: Assess the impact of BKZ on peripheral manifestations to week 104 of those studies. METHODS: BE MOBILE 1 (nr-axSpA) and 2 (r-axSpA) each comprised a 16-week double-blind, placebo-controlled period, then all received BKZ 160 mg every 4 weeks for 36 weeks. Patients not meeting withdrawal criteria could enter a combined open-label extension. We report change in enthesitis (Maastricht Ankylosing Spondylitis Enthesitis Score (MASES)) in patients with baseline MASES>0, peripheral arthritis (swollen joint count (SJC)/Disease Activity Index for Psoriatic Arthritis (DAPSA)) in patients with baseline SJC>0 and proportions achieving DAPSA disease states to week 104. Resolution of enthesitis (MASES=0)/arthritis (SJC=0) is reported to week 104 for those with baseline enthesitis/arthritis. We also report associations between peripheral manifestation resolution (MASES=0/SJC=0) and week 104 clinical outcomes in those with baseline enthesitis/arthritis. RESULTS: At baseline, 186/254 (73.2%) and 88/254 (34.6%) patients with nr-axSpA had enthesitis (MASES>0) and arthritis (SJC>0), respectively, compared with 199/332 (59.9%) and 66/332 (19.9%) patients with r-axSpA. Pooled BKZ/placebo-randomised patients with enthesitis (nr-axSpA/r-axSpA) showed average MASES improvement from 4.8/4.3 (baseline) to 1.6/1.3 (week 52) and 1.6/1.0 (week 104). Pooled BKZ/placebo-randomised patients with arthritis showed average SJC improvement from 4.0/4.5 (baseline) to 1.2/0.7 (week 52) and 0.9/0.6 (week 104). Over 60% of patients achieved DAPSA low disease activity/remission by week 52. Over 40%/60% patients achieved resolution of enthesitis (MASES=0)/arthritis (SJC=0) at week 104; enthesitis resolution was associated with larger improvements in week 104 clinical outcomes for patients with r-axSpA. CONCLUSION: BKZ resulted in sustained improvements in peripheral manifestations to 2 years across the full disease spectrum of axSpA.