S1827 An Update on a Multi-Center, Prospective, Non-Interventional Study of the Real-World Effectiveness of Etrasimod in Patients With Ulcerative Colitis (ENDEAVOUR-UC) Living in the United States

Introduction: Etrasimod is an oral, once-daily, selective sphingosine 1-phosphate (S1P)1,4,5 receptor modulator for the treatment of moderately to severely active ulcerative colitis (UC). ENDEAVOUR-UC (NCT06398626) is a prospective, multi-center, non-interventional cohort study evaluating the real-world (RW) effectiveness of etrasimod in adults with moderately to severely active UC in the United States (US). High-quality observational studies remain important to understand the etrasimod RW experience. ENDEAVOUR-UC enrolled its first patient in September 2024. This is an update. Methods: Eligible patients are aged ≥18 and <65 years and begin treatment for moderately to severely active UC as part of routine clinical care, with any disease extent. Around 250–300 patients will be enrolled from 30 US sites. ELEVATE UC phase 3 randomized controlled trial data informed sample size, based on an assumed 40% Week 12 symptomatic remission rate for achieving a 6.1% precision level (half-width of 95% confidence interval). The study includes 52 weeks of follow-up from etrasimod initiation, with 28-day safety follow-up. Baseline patient and disease characteristics are collected. Patients are evaluated overall and by line of prior therapy exposure. Endpoint and patient-reported outcome (PRO) data are collected via a web-based application at baseline, daily for 2 weeks, then at Weeks 4, 8, 12, 24, 36, and 52. The primary endpoint is symptomatic remission at Week 12. Secondary endpoints include symptomatic remission, steroid-free symptomatic remission, and steroid-free clinical remission at Weeks 24, 36, and 52 using the partial modified Mayo score (stool frequency + rectal bleeding scores) and symptomatic response, clinical remission, changes in fatigue, bowel urgency, and abdominal pain at Weeks 12, 24, 36, and 52. Additional data (endoscopy, fecal calprotectin, complete blood count) are collected and analyzed if part of standard of care. Results: As of April 2025, 30 sites have been selected, 23 are recruiting, and 25 patients are enrolled. Initial results on early-enrolled patients are expected in 2026, and final results in 2028. Principal investigators are diverse in geography and practice type to enhance patient diversity. Conclusion: ENDEAVOUR-UC will provide insights on early effectiveness and durability of etrasimod in a real-world setting, with PROs efficiently captured in real time via an innovative, specialized web-based application.