Clinical development of anticancer drugs can be enhanced using efficacy data of small population clinical trials

Although there are accelerated approval pathways based on data of small populations and surrogate endpoints, the concern that these pathways authorize the use of inefficacious drugs based on limited data from earlier phase clinical trials remains. We retrospectively investigated the efficacy of anticancer drugs, which were approved or whose development was terminated in small and large clinical trials, and verified whether small clinical trials could reflect the results for efficacy in large clinical trials.

All anticancer drugs approved in Japan or whose development was terminated from 2015 to 2019 were searched. The median overall survival (OS), median progression-free survival (PFS), and overall response rates (ORR) between small clinical trials (sample size ≤100) and large clinical trials (sample size >100) with identical target populations and treatment settings were compared. Simple linear regression analysis, Spearman's correlation analysis, and paired sample t-test were performed.

A total of 61 comparable small and large clinical trials were identified. For all endpoints, statistically significant linear trends and correlation were detected (p < 0.001). There were no statistically significant differences in the median PFS and ORR between small and large clinical trials. The mean differences of both clinical trials were -0.102 months and -1.531%, respectively.

Even when the sample size of the clinical trial was increased, the efficacy data of anticancer drugs could not be changed significantly. These results supported the accelerated approval pathway based on the promising efficacy data of small populations in anticancer drug development.