Does HLA-B27 Status Influence Ixekizumab Efficacy in Axial Spondyloarthritis? Results From the COAST-V, COAST-W, and COAST-X Trials.

INTRODUCTION: The human leukocyte antigen (HLA)-B27 is associated with axial spondyloarthritis (axSpA) and is a predictor of response to tumor necrosis factor inhibitors. However, limited data are available on HLA-B27 and interleukin-17 inhibitors. We evaluated the influence of HLA-B27 status on ixekizumab response through 52 weeks in patients with axSpA. METHODS: Data were analyzed from three randomized placebo-controlled trials: COAST-V (NCT02696785), COAST-W (NCT02696798), and COAST-X (NCT02757352). Patients fulfilled the Assessment of SpondyloArthritis international Society (ASAS) criteria for radiographic (r)-axSpA or non-radiographic (nr)-axSpA. Patients were randomized to receive 80 mg ixekizumab every 2 weeks, 80 mg ixekizumab every 4 weeks, or placebo. This post hoc analysis assessed the intent-to-treat population. The magnitude of benefit was calculated as the value for ixekizumab minus placebo. RESULTS: Among ixekizumab-treated patients with r-axSpA at week 16, ASAS ≥ 40% improvement (ASAS40) was achieved by 39.6% (n = 118/298) of HLA-B27-positive and 29.3% (n = 12/41) of HLA-B27-negative patients. The magnitude of benefit (ixekizumab-placebo) was 23.5% for HLA-B27-positive and 15.2% for HLA-B27-negative patients. At week 52, 44% of HLA-B27-positive and 31.7% of HLA-B27-negative patients achieved ASAS40. Similar trends were seen for Axial Spondyloarthritis Disease Activity Score low disease activity (ASDAS LDA; < 2.1) and Bath Ankylosing Spondylitis Disease Activity Index ≥ 50% improvement (BASDAI50). In ixekizumab-treated patients with nr-axSpA at week 16, ASAS40 response was achieved by 41.7% (n = 55/132) of HLA-B27-positive and 28.0% (n = 14/50) of HLA-B27-negative patients. The magnitude of benefit was 19.2% for HLA-B27-positive and 16.0% for HLA-B27-negative patients. At week 52, 52.3% of HLA-B27-positive and 32.0% of HLA-B27-negative patients achieved ASAS40. Similar trends were seen among patients with nr-axSpA for ASDAS LDA and BASDAI50. CONCLUSIONS: In patients with r-axSpA and nr-axSpA, ixekizumab improved response through 52 weeks for both HLA-B27-positive and HLA-B27-negative patients. However, the magnitude of benefit for ixekizumab versus placebo was numerically greater for HLA-B27-positive patients. TRIAL REGISTRATION: ClinicalTrials.gov identifiers, NCT02696785, NCT02696798, and NCT02757352.