Time to rethink washout periods in inflammatory bowel disease clinical trials: an international Delphi consensus

Background & Aims: Prolonged washout periods between advanced therapies and investigational drugs are commonly required in inflammatory bowel disease (IBD) randomized controlled trials (RCTs). These requirements restrict patient enrollment and diverge from real-world clinical practice. This study aimed to establish an international expert consensus on washout durations for advanced therapies and conventional immunosuppressants (IS) in IBD clinical trials and to propose methodological recommendations for future study designs. Methods: An international panel of 12 IBD clinical trial experts participated in a Delphi consensus process. Agreement of ≥75% among participants was predefined as consensus. Results: A total of 12 statements were approved. Consensus was reached to eliminate washout periods for conventional IS (thiopurines, tacrolimus, methotrexate, and mycophenolate mofetil). For golimumab and ozanimod, experts agreed on a 2-week washout period. For other biologics (infliximab, adalimumab, vedolizumab, ustekinumab, and anti–IL-23 agents), most participants favored a 2–4-week washout duration and for JAK inhibitors and etrasimod, participants supported a short 2-week washout, though without reaching formal consensus. Experts recommended incorporating washout-based stratification (<4 vs ≥4 weeks) at randomization into future trial designs to evaluate its impact on safety, pharmacokinetics, and efficacy outcomes. Conclusions: This international Delphi consensus highlights the need to adapt current washout practices in IBD RCTs to real-world practice. Experts supported shorter and standardized washout durations—preferably less than 4 weeks—to better align with clinical practice, while maintaining patient safety. Acceptance of these recommendations by regulators could harmonize washout duration criteria, enhance recruitment efficiency, and accelerate patient access to innovative therapies without compromising safety.