OBJECTIVES: Bimekizumab, a monoclonal IgG1 antibody, selectively inhibits IL-17F in addition to IL‑17A. A previously presented network meta-analysis established similar relative efficacy for ASAS outcomes at Week (Wk)16 with subcutaneous bimekizumab 160mg every four weeks (Q4W) versus subcutaneous ixekizumab 80mg Q4W, an IL-17A-only inhibitor, in patients with radiographic axSpA (r-axSpA; i.e. ankylosing spondylitis). This matching-adjusted indirect comparison (MAIC) assessed the relative efficacy of bimekizumab versus ixekizumab at Wk52.

METHODS: Individual patient data from BE MOBILE 2 (Bimekizumab 160mg; NCT03928743; n=220) were matched to pooled summary data from COAST-V and COAST-W (Ixekizumab 80mg following starting dose at Week 0; NCT02696785, NCT02696798; n=195). To adjust for cross-trial differences, patients from BE MOBILE 2 were reweighted to match baseline characteristics in the ixekizumab trials. Weights, determined by propensity score, were based on age, sex, ethnicity, previous TNFi exposure, weight, time-from-diagnosis, ASDAS and BASFI. These were selected by expert clinician consensus and literature review, but limited to characteristics reported by the COAST-trials. 52‑wk outcomes were recalculated for ASAS20, ASAS40, BASDAI50 and BASDAI change from baseline. Odds ratios (OR) or mean difference (MD) for unanchored comparisons are reported with 95% CI.

RESULTS: With bimekizumab (effective sample size [ESS]=45), patients had significantly higher likelihood of achieving: ASAS20 (OR [95% CI]: 2.14 [1.11, 4.12]), ASAS40 (2.03 [1.05, 3.91]), BASDAI50 (2.13 [1.10, 4.12]), and significantly higher likelihood of achieving greater reductions from baseline in BASDAI (MD [95% CI]: –0.74 [–1.46, –0.03]) than with ixekizumab at Wk52. However, the reduced ESS for bimekizumab following reweighting indicates limited overlap between trial populations, likely due to the higher number of patients with previous TNFi exposure included for ixekizumab.

CONCLUSIONS: Results suggest patients with r-axSpA treated with bimekizumab 160mg Q4W had a significantly greater likelihood of long-term response in ASAS and BASDAI outcomes than with ixekizumab 80mg Q4W at Wk52.