Background/Purpose: Bimekizumab (BKZ), a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)‑17F in addition to IL-17A, has shown efficacy to Week (Wk) 52 in patients (pts) with axial spondyloarthritis (axSpA).1 BKZ has shown comparable efficacy to 1 year (yr) across sexes,2 and to 2 yrs in differing symptom durations;3 the effect of other pt characteristics has not yet been reported. We report BKZ clinical outcomes to 1 yr in pts with axSpA stratified by age, BMI, CRP, and HLA-B27 status.

Methods: In BE MOBILE 1 and 2 (NCT03928704; NCT03928743), pts were randomized to subcutaneous BKZ 160 mg every 4 wks (Q4W) or placebo (PBO); all pts received BKZ Q4W from Wk 16–52. To Wk 52, we analyzed proportions of pts achieving ASAS40 and ASDAS < 2.1, and change from baseline (CfB) in ASDAS, BASDAI, ASQoL, and objective signs of inflammation (OSI; MRI SPARCC SIJ and MRI Berlin Spine). Pooled pts were stratified by baseline age (≤35, >35–≤45, >45 yrs), BMI (< 25, ≥25–< 30, ≥30 kg/m2), CRP (≤5, >5 mg/L), and HLA-B27 status (negative, positive). Binary endpoints used non‑responder imputation; continuous endpoints used multiple imputation. OSI measures used observed case.To compare Wk 16 BKZ treatment effect vs PBO stratified by subgroup, adjusted odds ratios and least squares (LS) mean differences were calculated using logistic regression and ANCOVA, respectively. No p values are provided due to the post hoc nature of analyses.

Results: Of 586 pooled pts, 349 and 237 were randomized to BKZ and PBO at baseline, respectively. Generally, larger improvements in clinical outcomes were seen for BKZ vs PBO across all subgroups at Wk 16; improvements were sustained/further improved to Wk 52 in all pts (Figures 1–3).For ASAS40/ASDAS < 2.1, numeric differences in the proportions of pts achieving outcomes were detected between BKZ vs PBO at Wk 16 across subgroups except age >45 yrs, BMI ≥30 kg/m2, and HLA‑B27 negativity (ASDAS < 2.1 only). Within respective subgroups, at Wk 52, proportions achieving ASAS40/ASDAS < 2.1 were numerically higher in BKZ-randomized pts with age ≤35 yrs, BMI ≥25–< 30 kg/m2, or HLA‑B27 positivity (Figure 1). For ASDAS/BASDAI/ASQoL, numeric differences in LS mean CfB were detected for BKZ vs PBO at Wk 16 across most subgroups except for age >45 yrs (BASDAI only), and BMI ≥30 kg/m2 (BASDAI/ASQoL only). Within respective subgroups, at Wk 52, numerically larger improvements in mean CfB ASDAS/BASDAI/ASQoL were observed in BKZ-randomized pts with age ≤35 yrs, BMI ≥25–< 30 kg/m2, CRP >5 mg/L, and HLA-B27 positivity (Figure 2). For OSI, numeric differences in LS mean CfB were detected for BKZ vs PBO at Wk 16 across subgroups except for age >45 yrs and HLA-B27 negativity, BMI ≥30 kg/m2 (MRI SPARCC SIJ only), and BMI < 25 kg/m2 and CRP ≤5 mg/L (MRI Berlin Spine only). Within respective subgroups, at Wk 52, numerically larger OSI improvements were seen in HLA-B27 positive pts only (Figure 3).

Conclusion: BKZ generally demonstrated greater improvements in clinical outcomes vs PBO at Wk 16. Improvements were sustained to 1 yr in pts with axSpA, regardless of pt demographics and baseline clinical presentation. References: 1. Baraliakos X. Ann Rheum Dis 2024;83:199−213. 2. Rudwaleit M. EULAR 2025; Poster POS0920. 3. Ramiro S. ACR 2024; Poster 2352.

Figure 1. Patients achieving ASAS40 (NRI) and ASDAS < 2.1 (MI) at Week 16 and Week 52, stratified by baseline characteristic subgroups

Figure 2. Mean change from baseline in ASDAS, BASDAI and ASQoL at Week 16 and Week 52, stratified by baseline characteristic subgroups (MI)

Figure 3. Mean change from baseline in MRI SPARCC SIJ and MRI Berlin Spine Score at Week 16 and Week 52, stratified by baseline characteristic subgroups (OC)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/bimekizumab-was-efficacious-regardless-of-age-bmi-crp-or-hla-b27-status-1-year-results-from-two-phase-3-studies/