A descriptive comparison of phase 3 results and head-to-head trials in inflammatory bowel diseases

With the increasing number of effective therapies for inflammatory bowel diseases (IBD), determining optimal treatment sequences is challenging. Given the impracticality of conducting randomized head-to-head trials for every comparison, this study assessed whether phase 3 placebo-controlled trials can reliably predict outcomes of published head-to-head studies.

Three randomized head-to-head trials without placebo arms were analyzed alongside their corresponding phase 3 placebo-controlled trials. Effect sizes for clinical and endoscopic endpoints were extracted for comparison.

In the VARSITY trial, vedolizumab achieved an 8.8% higher clinical remission rate than adalimumab at week 52 in patients with ulcerative colitis. Placebo-controlled studies estimated a 17.3% advantage for vedolizumab; however, differences in trial design and patient populations between GEMINI-1 and ULTRA-2 limited the robustness of this indirect comparison. In Crohn's disease, indirect comparisons of IM-UNITI, CLASSIC-II, and CHARM suggested an 11.6%-18.6% higher efficacy for adalimumab compared with ustekinumab in biologic-naïve patients, yet the SEAVUE head-to-head trial found no significant difference at week 52. Most recently, the SEQUENCE trial demonstrated a +15.6% superiority of risankizumab over ustekinumab in endoscopic remission at week 48 among bio-exposed Crohn's disease patients, whereas indirect comparisons between FORTIFY and IM-UNITI were confounded by clinically relevant population differences.

Significant heterogeneity in trial design, populations, and outcome reporting limits the predictive value of placebo-controlled trials. Randomized head-to-head trials remain essential for optimizing IBD therapeutic strategies.