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

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 versus placebo treatment effect) and Week 52 (treatment response in bimekizumab-randomised 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-randomised male patients typically had better treatment responses versus 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. CONCLUSIONS: 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.