Long-term safety and sustained efficacy of bimekizumab in patients with ankylosing spondylitis (radiographic axial spondyloarthritis): 5-year results from BE AGILE (phase 2b) and its open-label extension

Objective Assess long-term safety, tolerability and efficacy of bimekizumab in ankylosing spondylitis (radiographic axial spondyloarthritis (r-axSpA)). Methods Patients with active r-axSpA completing the dose-ranging 48-week randomised controlled trial could enrol in the open-label extension, where patients received bimekizumab 160 mg every 4 weeks. Safety (exposure-adjusted incidence rates/100 patient-years (EAIRs)) and efficacy outcomes (binary: non-responder imputation (NRI) and observed case (OC); continuous: multiple imputation (MI)) are presented through 256 weeks. Results From Weeks 0-256, 289/303 (95.4%) patients had ≥1 treatment-emergent adverse event (TEAE); most frequent were nasopharyngitis (21.8%) and upper respiratory tract infection (14.5%). The EAIR of fungal infections was 7.4 ( Candida infections: 2.6; oral candidiasis: 2.2); none systemic. EAIR of serious infections was 1.4; no active tuberculosis was reported. Active inflammatory bowel disease and anterior uveitis EAIRs were 0.8 and 0.7, respectively. 202/303 (66.7%) patients completed Week 256. 42 (13.9%) patients discontinued treatment due to TEAEs.Efficacy at Week 48 was maintained for 5 years. At Week 256, NRI analysis showed 49.7% (OC: 73.1%) and 41.6% (OC: 71.1%) of patients achieved Assessment of SpondyloArthritis International Society 40% (ASAS40) response and Axial Spondyloarthritis Disease Activity Score (ASDAS) low disease activity, respectively. Mean (SE; MI) ASDAS improved from 3.9 (0.1) at baseline to 2.1 (0.1) at Week 48, which was maintained to Week 256. Improvements in pain, fatigue, physical function and health-related quality of life were sustained. Conclusions The safety profile of bimekizumab after 5 years of treatment remained consistent with previous reports, with no new safety signals identified. 5-year efficacy was sustained in this r-axSpA population following robust disease control achieved at Week 48. Trial registration numbers NCT02963506; NCT03355573.