Lba0003 Minimal Spinal Radiographic Progression in Patients With Radiographic Axial Spondyloarthritis Over 2 Years of Bimekizumab Treatment: Results From a Phase 3 Open-Label Extension Study

Background: Pre-clinical data suggest that dual inhibition of interleukin (IL)-17A and IL-17F may have stronger inhibitory effects on new bone formation in axial spondyloarthritis (axSpA) versus IL-17A inhibition alone 1. Bimekizumab (BKZ), a monoclonal IgG1 antibody that selectively inhibits IL-17F in addition to IL-17A, has demonstrated long-term sustained efficacy in patients with radiographic axSpA (r-axSpA) up to 5 years 2. However, the impact of BKZ on structural progression in the spine, as assessed by radiography, has not been previously reported in patients with r-axSpA. Objectives: To evaluate the impact of BKZ treatment on 2-year radiographic progression in the spine of patients with r-axSpA in the open-label extension (OLE) of the phase 3 BE MOBILE 2 study. Methods: The BE MOBILE 2 (NCT03928743) study design has been reported previously 3. At Week (Wk) 52, eligible patients could enrol in an ongoing OLE (NCT04436640), where all patients received subcutaneous BKZ 160 mg Q4W. Radiographs of the spine were taken at baseline (BL) and Wk 104, with spinal radiographic progression assessed using modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). At both timepoints, 2 central readers were used, with an adjudicator if change scores differed by ≥5 mSASSS points. All readers were blinded to timepoint. The average of change scores across readers was determined for each radiograph; if 3 readers were used, an average of the 2 closest scores was calculated. We report mean and cumulative probability of change from baseline (CfB) in mSASSS at Wk 104 in the OLE, as well as the proportion of non-progressors, using definitions mSASSS CfB ≤0.5 and mSASSS CfB 2.1), BL hs-CRP (≤5 versus >5 mg/L), prior TNFi use and ASDAS and ASAS40 response at Wk 104, were assessed using logistic regression models. Results: Of 332 patients with r-axSpA randomised in BE MOBILE 2, 286 (86.1%) entered the OLE and 267 (80.4%) completed Wk 104. Of these, 71.9% (192/267) of patients were male and 16.1% (43/267) were TNFi-inadequate responders (IR). At Wk 104, 71.2% (190/267) of patients with r-axSpA had an mSASSS available. In these patients, the mean (SD) mSASSS score at BL was 7.3 (13.8) and CfB at Wk 104 was 0.3 (1.9). The majority of patients (157/190) had no spinal radiographic progression at Wk 104 with BKZ (Figure). The proportion of non-progressors at Wk 104, defined as mSASSS CfB ≤0.5, was 85.3% (162/190). The proportion of non-progressors at Wk 104, defined as mSASSS CfB 0.05). Conclusion: Minimal spinal radiographic progression and a high proportion of non-progressors, including in those with baseline spinal damage, was demonstrated at 2 years of treatment with BKZ in patients with r-axSpA. REFERENCES: 1 Shah M. RMD Open 2020;6:e001306. 2 Deodhar A. Arthritis Rheumatol 2023;75(suppl 9). 3 van der Heijde D. Ann Rheum Dis 2023;82(4):515–26. Acknowledgements: Funded by UCB Pharma. Medical writing support provided by Costello Medical and funded by UCB Pharma. Disclosure of Interests: Xenofon Baraliakos Paid instructor for AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma, Speakers bureau from AbbVie, BMS, Chugai, Eli Lilly, Galapagos, MSD, Novartis, Pfizer and UCB Pharma, Consultant of AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, Novartis, Pfizer and UCB Pharma, Grant/research support from Novartis and UCB Pharma, Sofia Ramiro Consultancy from AbbVie, Eli Lilly, Novartis, Pfizer, Sanofi and UCB Pharma, Grants from AbbVie, Galapagos, MSD, Novartis, Pfizer and UCB Pharma, Walter P Maksymowych Chief Medical Officer for CARE ARTHRITIS, Honoraria/consulting fees from AbbVie, BMS, Boehringer-Ingelheim, Celgene, Eli Lilly, Galapagos, Janssen, Novartis, Pfizer and UCB Pharma, Research grants from AbbVie, Pfizer and UCB Pharma; educational grants from AbbVie, Janssen, Novartis and Pfizer, Mikkel Østergaard Speakers bureau for Abbott, BMS, Merck, Mundipharma, Pfizer and UCB Pharma, Consulting fees from Abbott, Pfizer, Merck, Roche and UCB Pharma, Research grants from Abbott, Pfizer and Centocor, Ute Massow Employee of UCB Pharma, Carmen Fleurinck Shareholder of UCB Pharma, Employee of UCB Pharma, Tom Vaux Shareholder of UCB Pharma, Employee of UCB Pharma, Chetan Prajapati Contractor for UCB Pharma and employee of Veramed LTD, Alexander Marten Employee of UCB Pharma, Natasha de Peyrecave Employee of UCB Pharma, Denis Poddubnyy Speaker for AbbVie, BMS, Eli Lilly, MSD, Novartis, Pfizer and UCB Pharma, Consultant for AbbVie, Biocad, Eli Lilly, Gilead, GSK, MSD, MoonLake, Novartis, Pfizer, Samsung Bioepis and UCB Pharma, Grant/research support from AbbVie, Lilly, MSD, Novartis and Pfizer.