Defining information fractions in group sequential clinical trials with multiple endpoints.

The group sequential design has been well understood and widely applied in designs of late phase clinical trial to enable potentially early stopping for efficacy or futility. The information fraction (IF) is one of the key elements to determine the decision boundary at the interim analyses. The family-wise error rate (FWER) control is highly critical for clinical trials with multiple endpoints to be tested. In this article, we illustrate the importance of properly defining the information fraction for each individual endpoint regarding the FWER control through the numerical evaluation and a case study.