Efficacy of Ixekizumab in Chinese Patients with Radiographic Axial Spondyloarthritis by Baseline C-Reactive Protein Level.

Background: Ixekizumab, an interleukin 17A inhibitor, improved the Assessment of SpondyloArthritis international Society 40 (ASAS40) response rates irrespective of baseline inflammation in international populations with radiographic axial spondyloarthritis (r-axSpA). We investigated the association of baseline inflammation (measured by serum C-reactive protein [CRP] levels) with ixekizumab efficacy in Chinese patients with r-axSpA.

Methods: This was a subgroup analysis of a Chinese phase 3 study. Adults with r-axSpA who were biologic-naïve, or tumor necrosis factor inhibitor-experienced with baseline CRP > 5 mg/l, were randomized (1:1) to receive ixekizumab 80 mg every 4 weeks (IXEQ4W) or placebo, for 16 weeks. The following endpoints were analyzed by normal (≤ 5 mg/l) or elevated (> 5 mg/l) baseline CRP levels: ASAS40; Bath Ankylosing Spondylitis Disease Activity Index 50 (BASDAI50); Ankylosing Spondylitis Disease Activity Score (ASDAS) < 2.1; ASDAS clinically important improvement (CII; change from baseline ≥ 1.1); ASDAS major improvement (MI; change from baseline ≥ 2.0 or achievement of lowest possible score); Bath Ankylosing Spondylitis Metrology Index (BASMI) linear score; Bath Ankylosing Spondylitis Functional Index (BASFI); Short Form-36 Physical Component Score (SF-36 PCS).

Results: A total of 147 patients were randomized. At week 16, the ASAS40 response rate was greater with IXEQ4W versus placebo in the normal (50.0% vs. 15.0%; p < 0.05) and elevated (29.5% vs. 5.7%; p < 0.01) CRP subgroups. Significant improvements in BASDAI50 response rate, ASDAS < 2.1, and ASDAS CII with IXEQ4W versus placebo were observed in both subgroups (normal CRP: p < 0.05, p < 0.01, and p < 0.05, respectively; elevated CRP: p < 0.01, p < 0.001, and p < 0.001, respectively); IXEQ4W significantly improved ASDAS MI in the elevated CRP subgroup (p < 0.001). IXEQ4W significantly improved linear BASMI and BASFI scores in the normal CRP subgroup (p < 0.001 and p < 0.01, respectively), while SF-36 PCS improved in both subgroups (both p < 0.05).

Conclusions: Ixekizumab showed efficacy in Chinese patients with r-axSpA, irrespective of baseline CRP levels, consistent with results in international populations with r-axSpA. Background: ClinicalTrials.gov identifier, NCT04285229.