Clinical remission in paired phase two and three studies in inflammatory bowel disease: a systematic review with meta-analysis

Discrepancies in phase two and three studies can result in significant patient and financial burden, as well as the nonapproval of potentially efficacious drugs. We aimed to determine whether this discrepancy exists for clinical trials in inflammatory bowel disease (IBD). Electronic databases (MEDLINE and Embase) and clinical trial repositories were searched from 1 January 1946 to 12 March 2021, for paired phase two and three studies of advanced therapies for Crohn's disease and ulcerative colitis. The primary outcome was to compare clinical remission rates between paired phase two and three studies for Crohn's disease and ulcerative colitis. Multivariable mixed-model meta-analysis was performed to calculate odds ratios (OR) with 95% confidence intervals (CI). The Cochrane risk-of-bias tool was used to grade the risk of bias. Of 2642 studies, 29 were included. Fifteen were phase three, 11 were phase two, one was phase one/two, and two were phase two/three. There were no differences in clinical remission rates between phase two and three studies for Crohn's disease (OR, 1.07; 95% CI, 0.86-1.34; P = 0.54) and ulcerative colitis (OR, 0.81; 95% CI, 0.48-1.36; P = 0.43). Furthermore, there was a lack of any appreciable differences in study characteristics, inclusion criteria and patient demographics among paired phase two and three studies. Most studies were considered low risk of bias. Overall, paired phase two and three studies demonstrate similar clinical remission rates for advanced therapies in IBD. Whether this applies to newer outcomes, such as endoscopic and mucosal healing remains to be determined.