P167 Bimekizumab achieved sustained improvements in efficacy outcomes in patients with axial spondyloarthritis, regardless of prior tumour necrosis factor inhibitor treatment: week 52 pooled results from the phase 3 studies BE MOBILE 1 and BE MOBILE 2

Abstract Background/Aims Bimekizumab (BKZ) is a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F in addition to IL17A. In the phase 3 BE MOBILE 1 and 2 studies, BKZ treatment resulted in rapid and sustained improvements in efficacy outcomes through 52 weeks (wks) in patients with active nonradiographic axial spondyloarthritis (nr-axSpA) and radiographic (r)axSpA (i.e., ankylosing spondylitis AS). Here, we assess the efficacy of BKZ in tumour necrosis factor inhibitor (TNFi)-naïve or -inadequate responder (IR) patients with active nr-axSpA and raxSpA through Wk52. Methods In BE MOBILE 1 (nr-axSpA; NCT03928704) patients met Assessment of SpondyloArthritis international Society (ASAS) classification criteria and in BE MOBILE 2 (r-axSpA; NCT03928743) patients fulfilled modified New York and ASAS criteria. Patients were randomised to receive subcutaneous BKZ 160mg every 4wks (Q4W) or placebo (PBO) then BKZ 160mg Q4W from Wk16. This post-hoc analysis reports pooled mean efficacy data, including disease activity, MRI inflammation, physical function, and quality of life (QoL), through Wk52, stratified by TNFi status (naïve/IR). TNFi-IR patients were defined as those who experienced intolerance, or IR, to prior treatment given at an approved dose for ≥12wks. Results This pooled analysis included 505 TNFi-naïve and 81 TNFi-IR patients. 302/505 (59.8%) TNFi-naïve and 47/81 (58.0%) TNFi-IR patients were randomised to BKZ. Higher proportions of BKZ-randomised patients vs PBO achieved Wk16 ASAS40 (TNFinaïve: 46.0% vs 23.2%, TNFi-IR: 44.7% vs 14.7%; multiple imputation) and AS Disease Activity Score (ASDAS) 2.1 or low disease activity (47.9% vs 20.3%, 30.2% vs 15.6%; observed case). In continuous BKZ-treated patients, responses increased to Wk52 (ASAS40: 59.9%, 55.3%; ASDAS2.1: 62.0%, 54.1%). Greater reductions from baseline in ASDAS-CRP and MRI inflammation by Wk16 were achieved with BKZ vs PBO in both TNFi-naïve/-IR patients; in continuous BKZ-treated patients this was sustained or further improved through 52wks. Comparable improvements in physical function, nocturnal spinal pain and ASQoL were observed through 52wks with BKZ in TNFinaïve/-IR patients (Table). Conclusion Across the full axSpA disease spectrum, BKZ treatment resulted in clinically relevant improvements in key efficacy outcomes vs PBO, including suppression of inflammation and improvements in physical function and QoL, regardless of prior TNFi exposure. Improvements were sustained to Wk52. Disclosure M. Magrey: Consultancies; AbbVie, BMS, Eli Lilly, Novartis, Pfizer and UCB Pharma. Grants/research support; AbbVie, BMS and UCB Pharma. M. Van de Sande: Consultancies; AbbVie, Novartis and UCB Pharma. Member of speakers’ bureau; Janssen, Novartis and UCB Pharma. Grants/research support; Eli Lilly, Novartis and UCB Pharma. M. Breban: Consultancies; Novartis and UCB Pharma. Grants/research support; MSD. F. Van den Bosch: Consultancies; AbbVie, Amgen, Eli Lilly, Galapagos, Janssen, Novartis, Pfizer and UCB Pharma. Member of speakers’ bureau; AbbVie, Amgen, Janssen, Merck, Novartis, Pfizer and UCB Pharma. C. Fleurinck: Other; Employee of UCB Pharma. U. Massow: Other; Employee of UCB Pharma. N. de Peyrecave: Other; Employee of UCB Pharma. T. Vaux: Other; Employee of UCB Pharma. X. Baraliakos: Consultancies; AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, Novartis, Pfizer and UCB Pharma. Member of speakers’ bureau; AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma. Grants/research support; Novartis and UCB Pharma. Other; Paid instructor for AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma. H. Marzo-Ortega: Consultancies; AbbVie, Biogen, Eli Lilly, Janssen, Moonlake, Novartis, Pfizer, Takeda and UCB Pharma. Honoraria; AbbVie, Biogen, Eli Lilly, Janssen, Moonlake, Novartis, Pfizer, Takeda and UCB Pharma. Grants/research support; Janssen, Novartis and UCB Pharma.