Sample size adaptations and evaluation of pediatric study interpretability

To extend marketing exclusivity, a drug manufacture is required by the Food and Drug Administration to conduct an interpretable study of approved drugs that may benefit pediatric patients. In return for conducting an interpretable study, the drug manufacturer is rewarded with an additional 6 months of marketing exclusivity. If the study design uses a fixed sample size and nothing is changed during the study, it is relatively easy to determine whether an interpretable study was conducted. However, if the sample size can be changed based on an unblinded interim analysis, it is difficult to answer the question of whether the study was interpretable. We investigate the optimal design from the manufacturers perspective and find the strategy for sample size adaptation that optimizes the utility including the chance of an interpretable study.