E068 Achievement of low disease activity over 52 weeks in patients with active axial spondyloarthritis on bimekizumab treatment: results from the phase 3 studies BE MOBILE 1 and BE MOBILE 2

Abstract Background/Aims The recommended treatment target for axial spondyloarthritis (axSpA) is remission/low disease activity (LDA) according to Ankylosing Spondylitis Disease Activity Score (ASDAS) levels (ASDAS2.1); however, remission is difficult to achieve for many patients. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) remains commonly used in clinical practice to assess disease activity, although limited data exist to validate cut-offs. Bimekizumab (BKZ) is a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F in addition to IL-17A. BKZ has demonstrated consistent and sustained efficacy up to Week (Wk)52 in the BE MOBILE 1 and 2 phase 3 studies, including achievement of LDA according to ASDAS by 50% of patients with non-radiographic (nr-)axSpA and radiographic (r-)axSpA. Here, we report achievement of LDA, as assessed by either ASDAS2.1, BASDAI4, or both, to Wk52 with BKZ across the spectrum of axSpA in two phase 3 studies. Methods BE MOBILE 1 (NCT03928704) and BE MOBILE 2 (NCT03928743) comprised a 16-wk placebo (PBO)-controlled and 36-wk maintenance period. BE MOBILE 1 (nr-axSpA) patients met Assessment of SpondyloArthritis international Society (ASAS) classification criteria and had objective inflammation (MRI and/or elevated C-reactive protein). BE MOBILE 2 (r-axSpA) patients met modified New York and ASAS classification criteria. All patients had active disease (BASDAI≥4 and spinal pain≥4 BASDAI item 2) at baseline. Patients were randomised to subcutaneous BKZ 160 mg every 4 weeks (Q4W) or PBO. Patients randomised to PBO switched to BKZ from Wk16 (‘PBO/BKZ-switchers’). The proportion of patients that achieved LDA to Wk52, as defined by either ASDAS2.1, BASDAI4, or both, are presented (non-responder imputation). Results Overall, 254 patients with nr-axSpA (BKZ: 128/PBO: 126) and 332 with r-axSpA (BKZ: 221/PBO: 111) were randomised. Most had high (ASDAS≥2.1-≤3.5) or very high (ASDAS3.5) disease activity at baseline (nr-axSpA: BKZ: 99.2%/PBO: 97.6%; r-axSpA: BKZ: 98.6%/PBO: 100%). At Wk16, a greater proportion of BKZ vs PBO-treated patients achieved ASDAS2.1 (nr-axSpA: BKZ: 46.1%/PBO: 19.8%; r-axSpA: BKZ: 42.1%/PBO: 17.1%), BASDAI4 (nr-axSpA: BKZ: 52.3%/PBO: 31.7%; r-axSpA: BKZ: 55.7%/PBO: 41.4%) and both (nr-axSpA: BKZ: 43.8%/PBO: 19.0%; r-axSpA: BKZ: 41.6%/PBO: 17.1%). Results were sustained/improved across continuous BKZ-treated patients and PBO/BKZ-switchers to Wk52, with achievement of ASDAS2.1 (nr-axSpA: BKZ: 53.9%/switchers: 47.6%; r-axSpA: BKZ: 50.2%/switchers: 61.3%), BASDAI4 (nr-axSpA: BKZ: 60.2%/switchers: 54.0%; r-axSpA: BKZ: 65.6%/switchers: 68.5%) and both (nr-axSpA: BKZ: 49.2%/switchers: 45.2%; r-axSpA: BKZ: 49.8%/switchers: 58.6%). Achievement of BASDAI4 was consistently higher than ASDAS2.1, regardless of treatment arm. Conclusion Across the full axSpA disease spectrum, BKZ resulted in rapid achievement of LDA vs PBO to Wk16, as assessed by ASDAS2.1, BASDAI4, or both; improvements continued to Wk52. Most patients achieving ASDAS2.1 also achieved BASDAI4. These data suggest ASDAS2.1 is a more stringent criterion for LDA, relevant for consideration of BKZ in the context of a potential treat-to-target approach for axSpA in daily practice. Disclosure X. Baraliakos: Consultancies; AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, Novartis, Pfizer and UCB Pharma ; grant/research support from: Novartis and UCB Pharma. Member of speakers’ bureau; AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma. Other; Paid instructor for: AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma. S. Ramiro: Grants/research support; AbbVie, Galapagos, MSD, Novartis, Pfizer and UCB Pharma; Consultant for AbbVie, Eli Lilly, Novartis, Pfizer, Sanofi and UCB Pharma. M. Magrey: Consultancies; AbbVie, BMS, Eli Lilly, Novartis, Pfizer and UCB Pharma. Grants/research support; AbbVie, BMS and UCB Pharma. M. Rudwaleit: Consultancies; AbbVie, Eli Lilly, Novartis and UCB Pharma. Member of speakers’ bureau; AbbVie, Boehringer Ingelheim, Chugai, Eli Lilly, Janssen, Novartis, Pfizer and UCB Pharma. N. Haroon: Consultancies; AbbVie, Eli Lilly, Janssen, Novartis and UCB Pharma. C. Fleurinck: Other; Employees of UCB Pharma. U. Massow: Other; Employees of UCB Pharma. N. de Peyrecave: Other; Employees of UCB Pharma. T. Vaux: Other; Employees of 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. V. Navarro-Compán: Consultancies; AbbVie, Eli Lilly, Galapagos, MoonLake, MSD, Novartis, Pfizer and UCB Pharma. Member of speakers’ bureau; AbbVie, Eli Lilly, Fresenius Kabi, Janssen, MSD, Novartis, Pfizer and UCB Pharma. Grants/research support; AbbVie and Novartis.