OBJECTIVES: Scottish guidelines for axial spondyloarthritis (axSpA) management recommend sequential biologics use and include interleukin-17 inhibitors (IL-17i) in current practice. Using an adapted version of the York Model, we estimated the cost-effectiveness of bimekizumab, a monoclonal IgG1 antibody selectively inhibiting IL-17F in addition to IL-17A, in patients with non-radiographic (nr-) and radiographic (r-) axSpA versus secukinumab 150mg including recommended dose escalation to 300mg based on clinical response.

METHODS: A decision tree followed by a lifetime Markov model represented the axSpA treatment pathway, from first- to second-line biologics disease-modifying antirheumatic drug (bDMARD), then best supportive care (BSC) including 87% biologics (expert-based). Bimekizumab followed by any bDMARD was compared with secukinumab 150mg followed by a blend reflecting the recommended dose escalation to secukinumab 300mg based on European registries (57% secukinumab 300mg/43% bDMARD). Transition to the next therapy was triggered by BASDAI50 non-response or any-cause discontinuation (11%/year). A network meta-analysis provided clinical score changes and response rates. Utilities were derived from an ASDAS-CRP mapping to EQ-5D-3L. Disease management costs were estimated by a BASFI-based equation, plus biologics monitoring costs from the National Health Service of Scotland perspective (2021/22). Biologic list prices were used (British National Formulary 2023). 3.5%/year discounting was applied. Scenario (ASAS40-response, 47%-escalation) and one-way sensitivity analyses were performed.

RESULTS: In nr-axSpA, the incremental cost-effectiveness ratio (ICER) of the bimekizumab vs. secukinumab treatment pathway was £18,390/quality-adjusted life-year (QALY). Bimekizumab produced 0.73 (11.74 vs. 11.01) more QALYs for £13,404 additional cost vs. the secukinumab pathway. Results in r-axSpA were similar (ICER=£23,370; ΔQALY=0.70; ΔCost=£16,445). ICERs remained <£30,000/QALY in all tested scenarios. BASDAI50 response rate and percentage of bDMARDs in BSC were the main results drivers.

CONCLUSIONS: The bimekizumab pathway demonstrated cost-effectiveness across the full spectrum of axSpA in Scotland versus a secukinumab 150mg treatment pathway with recommended dose escalation to 300mg for inadequate responders.