Fragility index analysis for randomized controlled trials of approved biologicals and small molecule drugs in inflammatory bowel diseases.

Introduction: Biologics and small molecules have been increasingly applied in Crohn's disease (CD) and ulcerative colitis (UC). But the robustness of their trials has not been evaluated.

Methods: We initially collected all the approved biologics or small molecules for CD or UC up to December 1, 2022. Databases were then queried by keywords in chemical name and CD or UC. Randomized controlled trials (RCTs) in the two-arm, 1:1 design were included. Fragility index (FI) and fragility quotient (FQ) were subsequently calculated.

Results: We included twenty-eight RCTs, including nine pivotal trials listed in approval labels, nineteen non-pivotal trials not included in the labels. The median sample size was 99 [IQR, 60-262] and the median number of loss-of-follow-up (LFU) was 14 [IQR, 8-43]. Pivotal trials in the labels had the median FI of 8 [IQR, 4-14, n = 6] that was marginally higher than non-pivotal trials (3 [IQR, 2-4], p = 0.08). The median FQ was 0.0330 [IQR, 0.1220-0.0466] and 0.0310 [IQR, 0.0129-0.0540] for pivotal and non-pivotal trials, respectively (p = 1.0). The sample size and FI were significantly correlated (Spearman correlation coefficient [r] = 0.56, 95 %CI 0.21-0.78, p = 0.003). The number of total events was also significantly correlated with FI (r = 0.53, 95 %CI 0.17-0.77, p = 0.006). Study p-values were significantly associated with FI (p = 0.01): trials with p-values < 0.001 had the highest median FI of 10 [IQR, 6-17]. No factor was found strongly correlated with FQ.

Conclusion: Results from trials assessing administration-approved biologics or small molecules for treating CD or UC were vulnerable to small changes by measuring FI or FQ. Pivotal studies contributing to regulatory approvals exhibited a relatively higher degree of resilience compared to non-pivotal trials.