OBJECTIVES: The study aimed to compare the cost-per-responder (CPR) of bimekizumab, a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F in addition to IL-17A, against other licensed IL-17A inhibitors for the treatment of radiographic (r-) and non-radiographic (nr-) axial spondyloarthritis (axSpA) in the UK.

METHODS: A 16-week CPR model was developed based on a published network meta-analysis employing Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) as a primary outcome measure for a predominantly biologic naïve population with r-axSpA and nr-axSpA. BASDAI50 response rates were used to evaluate treatment efficacy. Drug costs and dose recommendations were based on the NHS list prices outlined in the British National Formulary (2024). The CPR was calculated by multiplying the number of doses required in the first 16 weeks of treatment by the drug cost, divided by the response rate. Treatments included in the analysis were bimekizumab (administered at 160mg monthly), ixekizumab (160mg for the first dose then 80mg monthly) and secukinumab (nr-axSpA and r-axSpA; 150mg weekly for 5 doses then a monthly maintenance dosing). Additionally, a monthly maintenance dose of secukinumab 300mg in r-axSpA population was also included, aligning with dosage recommendations found in the BNF and summary of product characteristics.

RESULTS: Bimekizumab demonstrated the lowest cost per responder for BASDAI50 in both the r-axSpA (£14,788) and nr-axSpA predominantly naïve populations (£13,163). Secukinumab demonstrated the highest cost per responder for BASDAI50 (£17,285) in the r-axSpA population whilst ixekizumab demonstrated the highest cost per responder for BASDAI50 (£19,795) in the nr-axSpA population.

CONCLUSIONS: Across the eligible UK predominantly naïve axSpA population, bimekizumab demonstrated the lowest cost per BASDAI 50 response at week 16 compared to other licensed IL-17A inhibitors based on NHS list prices. This aligns with NICE recommendations for treatment continuation in patients achieving a 50% reduction in BASDAI at week 16.