Treatment Persistence and Factors Associated with Bimekizumab Discontinuation in Psoriatic Arthritis and Axial Spondyloarthritis: A Real-World Multicenter Study

Background/Objectives: Real-world evidence on bimekizumab treatment persistence and longitudinal disease activity in spondyloarthritis remains limited. This study assessed 12-month treatment persistence, changes in disease activity, and factors associated with discontinuation in patients with psoriatic arthritis and axial spondyloarthritis treated in routine clinical practice. Methods: We conducted a single-arm observational ambispective multicenter cohort study including 207 patients who initiated bimekizumab between December 2023 and November 2024. Treatment persistence was evaluated using Kaplan–Meier analysis and exploratory Cox proportional hazards models. Changes in disease activity were assessed using paired complete-case analyses, supplemented by available-case generalized estimating equation sensitivity analyses. Results: At 12 months, treatment persistence was 81.2%. Discontinuation occurred in 39 patients and was mainly attributed to lack of effectiveness. Persistence differed by sex in univariate analysis, with higher retention in males. Axial psoriatic arthritis classification was associated with an increased risk of discontinuation compared with peripheral psoriatic arthritis in the exploratory adjusted Cox model (HR: 3.02; 95% CI: 1.28–7.14). Obesity was not significantly associated with treatment discontinuation. Significant within-patient reductions were observed in BASDAI, ASDAS-CRP, and DAPSA among patients with available assessments. Conclusions: At 12 months, 81.2% of patients remained on treatment, and disease activity scores decreased among evaluable patients. Because this study had no comparator arm, these changes cannot be causally attributed to bimekizumab. The association between axial psoriatic arthritis classification and lower persistence should be considered hypothesis-generating because of the limited number of events, low event-to-parameter ratios, and absence of standardized axial PsA classification criteria. Safety data were restricted to adverse events leading to treatment discontinuation.