Research in context
Evidence before this study
We searched PubMed for research articles published in English between database inception and Sept 4, 2019, using the terms: “non-radiographic axial spondyloarthritis” AND “biologic”. Of the 28 articles that resulted from the search, we selected those that described the disease and current treatments. Axial spondyloarthritis is a chronic inflammatory disease that predominately affects the sacroiliac joints and spine. For classification purposes, axial spondyloarthritis has been separated into radiographic and non-radiographic categories on the basis of whether or not a patient has definite sacroiliitis visible on radiographs. Tumour necrosis factor inhibitors are the only class of biologic drugs approved for the treatment of non-radiographic axial spondyloarthritis. Ixekizumab, a high-affinity monoclonal antibody that selectively targets interleukin 17A (IL-17A), has been approved in the USA for the treatment of patients with radiographic axial spondyloarthritis. However, to our knowledge, this study is the first to investigate the efficacy and safety of an IL-17 inhibitor in patients with non-radiographic axial spondyloarthritis.
Added value of this study
The COAST-X study met the primary endpoints, showing superiority of ixekizumab over placebo for achievement of Assessment of SpondyloArthritis international Society-40 response at weeks 16 and 52 in patients with non-radiographic axial spondyloarthritis and objective signs of inflammation. The major secondary endpoints were also met, with ixekizumab showing efficacy in reducing disease activity and sacroiliac joint inflammation and improving patient function and quality of life. The safety profile of ixekizumab in COAST-X was consistent with studies of ixekizumab in patients with moderate-to-severe psoriasis, psoriatic arthritis, and radiographic axial spondyloarthritis. COAST-X is the first study to show efficacy of an IL-17 inhibitor in patients with non-radiographic axial spondyloarthritis, where only evidence for TNF inhibitors previously existed.
Implications of all the available evidence
The COAST-X study shows that IL-17A has a role in the pathogenesis of non-radiographic axial spondyloarthritis. Treatment with ixekizumab resulted in significant improvements in disease activity, physical function, quality of life, and inflammation in the sacroiliac joints compared with placebo. Overall, our findings indicate that ixekizumab could be a new treatment option for patients with non-radiographic axial spondyloarthritis.