Endoscopic and Histological Placebo Rates in Crohn's Disease Clinical Trials: A Systematic Review and Meta-analysis

Background Precise estimates of placebo response rates help efficient clinical trial design. In this systematic review and meta-analysis, we assessed contemporary placebo endoscopic and histological response rates in Crohn's disease (CD) clinical trials. Methods MEDLINE, EMBASE, and Cochrane CENTRAL were searched from inception to April 2022 to identify placebo-controlled studies of pharmacological interventions for CD. Endoscopic response, remission, and mucosal healing rates for participants assigned to placebo in induction and maintenance studies were pooled using a random-effects model. Point estimates and associated 95% confidence intervals (CIs) were calculated. Results In total, 16 studies (11 induction, 3 maintenance, 2 induction and maintenance) that randomized 1646 participants to placebo were eligible. For induction trials, the pooled placebo endoscopic response, endoscopic remission, and mucosal healing rates in participants assigned to placebo were 13% (95% CI, 10-16; I-2 = 14.1%; P = .14), 6% (95% CI, 3-11; I-2 = 74.7%; P < .001), and 6% (95% CI, 4-9; I-2 = 26.9%; P = .29), respectively. The pooled endoscopic remission rate in patients who were bio-naive was 10% (95% CI, 4-23) compared with only 4% (95% CI, 3-7) in bio-experienced patients. For maintenance trials, the pooled endoscopic response, remission, and mucosal healing rates were 7% (95% CI, 1-31; I-2 = 78.2%; P = .004), 11% (95% CI, 4-27; I-2 = 70.8%; P = .06), and 7% (95% CI, 3-15; I-2 = 29.7; P = .23), respectively. Only 3 trials assessed histological outcomes. Conclusions Endoscopic placebo rates vary according to trial phase and prior biologic exposure. These contemporary data will serve to inform CD trial design, sample size calculation, and end point selection for future trials.