Exploring the Effects of Ixekizumab on Pain in Patients with Ankylosing Spondylitis Based on Objective Measures of Inflammation: Post Hoc Analysis from a Large Randomized Clinical Trial

Introduction: The objective of this analysis is to evaluate the improvement in spinal pain with ixekizumab, placebo, and adalimumab based on objective measures of inflammation response in patients with ankylosing spondylitis (AS). Methods: The COAST-V 52-week, double-blind, placebo-controlled, randomized phase III trial examined the efficacy of ixekizumab in patients with active AS; adalimumab was used as an active reference arm. Treatment effects on reduction in pain were assessed by objective measures of controlled and persisting inflammation (defined by magnetic resonance imaging [MRI], C-reactive protein [CRP], or MRI + CRP status). Pathway analysis was used to analyze treatment effect that was not attributable to reduction in inflammation biomarkers. Results: In patients with AS, when inflammation was controlled as assessed by MRI, patients treated with ixekizumab experienced a reduction in spinal pain at night (SP-N, numeric rating scale, ixekizumab mean = − 3.9, p < 0.001, adalimumab mean = − 2.6, p < 0.05) compared to placebo (mean = − 1.6) at week 16. When inflammation was controlled as assessed by MRI + CRP, ixekizumab and adalimumab had numerically greater reductions at week 16 in SP-N versus placebo. All ixekizumab groups had further improvements at week 52. When inflammation was persisting as assessed by MRI + CRP, ixekizumab-treated patients had significant reduction in SP-N (mean = − 3.7, p < 0.001) versus placebo (mean = − 1.7), improvement with adalimumab did not reach significance (mean = − 2.6, p = 0.06). In the pathway analysis at week 16, ixekizumab had a greater effect on pain outcomes compared to adalimumab. Conclusion: This post hoc analysis is supportive of the hypothesis that ixekizumab reduces pain in AS by additional mechanisms other than the reduction of measurable inflammation. Trial Registration Number: NCT02696785.