Background/Purpose: In this analysis, we evaluate the efficacy of ixekizumab at week 16 in patients with non-radiographic axial spondyloarthritis (nr-axSpA) with or without baseline HLA-B27 positivity and disease duration using a 5 year cutoff.

Methods: COAST-X (NCT02757352) was a phase 3, randomized, double-blind, placebo-controlled study of eligible patients with active nr-axSpA who received 80 mg ixekizumab every 4 weeks (IXE Q4W, N=96) or every 2 weeks (IXE Q2W, N=102), or placebo (PBO, N=105) up to 52 weeks. Post hoc analysis was performed on the intent-to-treat population at week 16 and included two subpopulations of patients based on baseline HLA-B27 status (positive or negative) or disease duration (< 5 or ≥5 years). Outcomes reported here are achievement of Assessment of SpondyloArthritis international Society 40% response (ASAS40) and Bath Ankylosing Spondylitis Disease Activity Index 50% response (BASDAI50) at week 16. Missing data were imputed using non-responder imputation. Treatment comparison was performed using Fisher’s exact test.

Results: Of patients treated with IXE Q4W, IXE Q2W, and PBO through week 16, 74.0% (n=71), 71.6% (n=73), and 73.3% (n=77) respectively were HLA-B27+, and 25.0% (n=24), 27.5% (n=28), and 25.7% (n=27) respectively were HLA-B27-. Of patients treated with IXE Q4W, IXE Q2W, and PBO through week 16, 42.7% (n=41), 40.2% (n=41), 37.1% (n=39) respectively had disease duration < 5 years and 57.3% (n=55), 59.8% (n=61), 62.9% (n=66) had disease duration ≥5 years. ASAS40 and BASDAI50 response rates were higher with IXE Q4W and IXE Q2W vs. PBO at week 16 regardless of HLA-B27 status or disease duration < 5 or ≥5 years (Figure). Patients who were HLA-B27+ showed a significant difference over PBO for ASAS40 response (IXE Q4W, p=.047; IXE Q2W, p=.005) and BASDAI50 response (IXE Q4W, p=.020; IXE Q2W, p=.003) at week 16. Patients who had disease duration < 5 years showed a significant difference over PBO for ASAS40 response (IXE Q4W, p=.029; IXE Q2W, p=.029) and BASDAI50 response (IXE Q4W, p=.001; IXE Q2W, p=.003) at week 16, and patients who had disease duration ≥5 years showed a significant difference over PBO for ASAS40 response for IXE Q2W (p=.019) at week 16.

Conclusion: Patients treated with ixekizumab saw improvement in signs and symptoms of nr-axSpA as assessed by ASAS40 and BASDAI50 responses regardless of HLA-B27 status (positive or negative) or disease duration (< 5 or ≥5 years). However, the responses with IXE Q4W and IXE Q2W were significant over placebo for the HLA-B27+ patients and those with < 5 years of disease.

Figure. ASAS40 (A) and BASDAI50 (B) response rates at week 16 with IXE versus PBO in subpopulations of patients with non-radiographic axial spondyloarthritis. ASAS40, Assessment of SpondyloArthritis international Society 40% response, BASDAI50, Bath Ankylosing Spondylitis Disease Activity Index 50% response, IXE, ixekizumab; N, number of patients in the analysis population; n, number of patients in the specified category; PBO, placebo; Q2W, every 2 weeks; Q4W, every 4 weeks. *p < .05, **p < .01 vs. PBO

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/response-to-treatment-with-ixekizumab-in-patients-with-active-non-radiographic-axial-spondyloarthritis-based-on-hla-b27-status-and-disease-duration/