Placebo rates in randomised clinical trials of ulcerative colitisSolitano, Virginia (Avtor) Hogan, Malcolm (Avtor) Singh, Siddharth (Avtor) Danese, Silvio (Avtor) Peyrin-Biroulet, Laurent (Avtor) Vuyyuru, Sudheer Kumar (Avtor) MacDonald, John K (Avtor) Zou, Guangyong (Avtor) Hanžel, Jurij (Avtor) inflammatory bowel diseaseplacebo effectclinical trialsulcerative colitisBackground and aims: We assessed placebo rates and associated factors using individual patient data (IDP) from randomised clinical trials (RCTs) in ulcerative colitis (UC). Methods: We conducted an IPD meta-analysis using Vivli and Yale University Open Data Access data-sharing platforms. Phase 2 and 3 RCTs of advanced biologics in adults with moderate-to-severe UC published since 2010 were included. Pooled placebo rates and 95% CIs were estimated using one-and two-stage meta-analytical approaches. Significant patient-level factors (P < 0·05) were identified using regression analyses. Primary outcomes were clinical response and remission. Results: Data were available for 1703 patients from nine studies. For induction trials, overall placebo response and remission rates were 33% (95% CI 29%–38%) and 9% (95% CI 7%–11%). Overall placebo response and remission rates in maintenance trials were 28% (95% CI 18%–41%) and 14% (95% CI 9%–20%). A lower body mass index reduced odds of placebo response and remission, while higher baseline albumin levels and left-sided (compared to extensive) UC increased the odds of these outcomes. A one-point increase in the Mayo Clinic Score (MCS) and adapted MCS was associated with a 26% and 27% reduction in odds of clinical remission. For induction trials, prior biologic exposure was associated with lower odds of response and remission. Multi-centre trials have lower placebo effects than single-centre trials. Conclusions: These results enable future trials to incorporate design elements that reduce placebo rates as well as a precise benchmark for expected rates in clinical trials that do not include placebo.20252026-01-13 08:59:26Neznano25169sl