Endoscopic endpoints in biologic clinical trials and beyond: the case for Crohn's Disease

IntroductionStandardized evaluation of endoscopic disease activity using valid, responsive and reliable instruments is crucial for optimizing the efficiency of clinical trials with therapeutic agents for Crohn's disease (CD). Achieving endoscopic remission and/or mucosal healing is associated with improved long-term outcomes, making it an important treatment goal.Areas coveredSeveral endoscopic indices have been used over the past two decades, though they lack complete validation. The Crohn's Disease Endoscopic Index of Severity (CDEIS) and Simple Endoscopic Score for Crohn's Disease (SES-CD) demonstrate fair reliability and responsiveness to treatment. The CDEIS is rather complex and time-consuming, and both endoscopic indices are prone to variability. The Lewis Score and Capsule Endoscopy CD Activity Index (CECDAI) provide useful alternative instruments using video capsule endoscopy, but they need further validation. The Rutgeerts score predicts post-surgical recurrence but lacks evaluation for follow-up.Expert opinionWhile recent guidelines emphasize co-primary clinical and endoscopic endpoints to improve trial effectiveness, these are typically based on expert consensus rather than empirical data. We advocate to use SES-CD as the preferred endoscopic index given its simplicity, strong correlation with CDEIS, and treatment responsiveness. Future research should focus on establishing clinically relevant cutoff values for endoscopic response and endoscopic remission in CD trials, including post-operative settings.