Comparison of treatment effect between phase 2 and phase 3 trials in patients with inflammatory bowel disease

The accumulation of multiple randomized controlled trials in the field of inflammatory bowel diseases provides an opportunity to compare treatment effects between phase 2 and 3 trials. We aimed to determine whether treatment effects observed in phase 3 investigating biologics and small molecule drugs differed from those in their preceding phase 2 trial.

We first performed a review of phase 2 and phase 3 trials enrolling ulcerative colitis (UC) or Crohn's disease (CD) patients. We compared the percent overall success for key endpoints between phases (several phase 3 could be matched to a single phase 2 trial). Then, we compared the percent overall success in the matched phase 2 and 3 trials (ratio 1:1), and performed sensitivity analysis.

We identified 14 phase 2 (8 CD; 6 UC) and 24 phase 3 (13 CD; 11 UC) trials. In CD, the different analyses suggest that the percentage of overall success of clinical remission and clinical response was significantly higher in phase 2 than in phase 3 trials. In UC, the analyses suggest collectively that the percent of treatment effect seemed similar for clinical remission, clinical response and histologic outcomes between phases but with a lower percentage of overall success in phase 2 than in phase 3 trials for endoscopic endpoints.

In UC, we observed a similar percentage of treatment effect for clinical and histologic outcomes between phase 2 and 3 trials but not for endoscopic outcomes. Whereas in CD, we showed a failure to reproduce similar results between phases. These results may help sponsors in the design of future drug development programs.