Bimekizumab efficacy in male and female patients with axial spondyloarthritis: 52-week results from the phase 3 BE MOBILE trials

Objectives: To assess sex-based differences in response to bimekizumab in patients with axial spondyloarthritis (axSpA) from two phase 3 trials. Methods: Improvements to week 52 in measures of disease activity (ASAS40, ASDAS <2.1, BASDAI) and function (BASFI), pain, fatigue, health-related quality of life (HRQoL) and objective signs of inflammation (MRI, hs-CRP) were assessed post hoc in patients with non-radiographic (nr-) and radiographic (r-)axSpA from BE MOBILE 1 (NCT03928704) and BE MOBILE 2 (NCT03928743), respectively. Comparisons were made between sexes at week 16 (bimekizumab vs placebo treatment effect) and week 52 (treatment response in bimekizumab-randomized patients only) using odds ratios for dichotomous outcomes and difference values for continuous outcomes. For hs-CRP, ratio to baseline was calculated due to skewed distribution. Results: While sex distribution was balanced in nr-axSpA (54.3% male), 72.3% of patients with r-axSpA were male. At week 16, bimekizumab-randomized male patients typically had better treatment responses vs placebo compared with female patients across ASAS40, ASDAS <2.1 and improvements in BASDAI, BASFI and measures of HRQoL. At week 52, female patients had longer-term improvements across these outcomes, though male patients continued to have numerically higher treatment responses. In contrast, active inflammation (MRI, hs-CRP) was reduced to similarly low levels in both sexes at week 16 and maintained to week 52, despite baseline differences. Conclusion: Although male patients had earlier clinical responses to bimekizumab treatment, female patients demonstrated longer-term improvements in composite and patient-reported outcomes. Both sexes had substantial improvements in objective inflammation at week 16 and 52, despite baseline differences. Trial registration: Clinicaltrials.gov; NCT03928704 and NCT03928743 © The Author(s) 2026. Published by Oxford University Press on behalf of the British Society for Rheumatology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.