Pos0204 Effectiveness of TNF Inhibition in Very Early Axial Spondyloarthritis (Less Than One Year of Axial Symptom Duration): Results From a Large National Observational Cohort

Background: It remains uncertain whether the concept of a "window of opportunity", as defined for rheumatoid arthritis, applies to axial spondyloarthritis (axSpA). The Assessment in SpondyloArthritis international Society (ASAS) has published a consensus definition for "early" axSpA, which relies on axial symptom duration of ≤2 years 1. Recent research using this definition has indicated that the effectiveness of treatment with tumor necrosis factor inhibitors (TNFi) is comparable in early and established disease 2. To further explore the potential for improved outcomes in patients diagnosed and treated at an earlier stage, we here evaluate a shorter cut-off for the definition of early axial symptom duration. Objectives: To analyze the effectiveness of treatment with a first TNFi in patients with "very early" axSpA, defined as an axial symptom duration ≤1 year, in comparison to patients with established axSpA (axial symptom duration >2 years). Methods: Patients from a large national observational cohort of patients diagnosed as having axSpA were included in the current study if data on duration of axial symptoms was available and a first TNFi initiated between 2004 and 2023. Patients were stratified according to axial symptom duration: very early axSpA (≤1 year), early axSpA (>1 year and ≤2 years), and established axSpA (≥2 years). Drug retention was analyzed using Cox proportional hazards models, adjusting for age, sex, human leucocyte antigen B27 (HLA-B27) positivity, body mass index (BMI), education, smoking status, elevated C-reactive protein (CRP), and inflammation on magnetic resonance imaging (MRI) of the sacroiliac joints in patients with complete covariate information. Adjusted logistic regression analyses were employed to determine the achievement of the Bath Ankylosing Spondylitis Disease Activity Index criteria for 50% improvement (BASDAI50) at 12±6 months (intention-to-treat analyses in patients with available visits). Results: A total of 1080 patients met the inclusion criteria, with 131 in the very early axSpA group (12.1%), 75 in the early axSpA group (6.9%) and 874 in the established axSpA group. Characteristics of patients at the initiation of the first TNFi are presented in Table 1. Patients in the very early axSpA group were significantly younger, and had less impairment of spinal mobility. TNFi retention was analyzed in 594 patients with available covariate information (75 patients with very early axSpA, 31 patients with early axSpA and 488 patients with established disease; Table 2). We did not find evidence for a difference in retention between very early and established axSpA (HR for drug discontinuation 0.84, 95% CI 0.62-1.15, Table 2). Adjusted BASDAI50 response at 1 year was investigated in 422 patients with complete covariate data (55 patients with very early axSpA, 18 patients with early axSpA and 349 patients with non-early axSpA). A comparable BASDAI50 response was observed in very early vs. established axSpA (OR 0.85, 95% 0.44-1.64), and in early vs. established axSpA (OR 0.79, 95% 0.27-2.25). Table 1. Characteristics of axSpA patients with very early disease and non-early disease at initiation of the first tumor necrosis factor inhibitor. ASDAS = Ankylosing Spondylitis Disease Activity Score; axSpA = axial spondyloarthritis; BASDAI = Bath Ankylosing Spondylitis Disease Activity Index; BASFI = Bath Ankylosing Spondylitis Functional Index; BASMI = Bath Ankylosing Spondylitis Metrology Index; CRP = C-reactive protein; HLA-B27 = human leucocyte antigen-B27; MRI = magnetic resonance imaging). Table 2. Comparison of TNFi retention in patients with very early and early axSpA versus patients with established axSpA. Conclusion: Potential differences in effectiveness of TNFi in patients with very early and established axSpA are probably of a modest effect size, since, in our cohort, we did not find evidence for a difference between the two groups. REFERENCES: 1 Ann Rheum Dis 2023;doi:10.1136/ard-2023-224.232. 2 RMD Open 2023;9:e003455. Acknowledgements: NIL. Disclosure of Interests: Adrian Ciurea: None declared, Andrea Goetschi: None declared, Burkhard Moeller Speaking fees Janssen, Novartis, Pfizer, Eli Lilly, Grant/research support from Amgen, Michael J. Nissen Speaking fees from AbbVie, Amgen, Eli Lilly, Janssen, Novartis, Pfizer, Consulting fees from AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, Research grant from Novartis and Pfizer, Kristina Buerki: None declared, René Braem: None declared, Michael Andor: None declared, Thomas Hügle Payments for lectures and presentations from Pfizer, Fresenius Kabi, AbbVie, Merck Sharp and Dohme, Galapagos, Eli Lilly, Novartis, Holds stocks or stock options from Atreon SA and Vtuls, royalties from Curmed, Participated on Advisory board for DETECTRA, Andrea Rubbert-Roth Honoraria for lectures from AbbVie, Janssen, Novartis, Pfizer, Consulting fees from AbbVie, Janssen, Pfizer, Support for attending meetings from Janssen, Pfizer, Diego Kyburz Honoraria for presentations from AbbVie, Eli Lilly, Participation on advisory boards from AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, Roche, Research grant from AbbVie, support for attending meetings from Janssen and Eli Lilly, Sabine Adler: None declared, Oliver Distler: None declared, Almut Scherer Employed by Bristol-Myers-Squib in 2007-2008, Raphael Micheroli Honoraria for lectures or presentations from AbbVie, Eli Lilly, Janssen, Gilead, and Pfizer.