Bayesian Optimal Phase II Design for Randomized Clinical Trials

Randomized clinical trials are the gold standard to evaluate the efficacy of an experimental treatment. We propose a flexible Bayesian optimal phase II (BOP2) design for two-arm randomized trials. The proposed two-arm BOP2 design is flexible and can handle single, multiple primary and coprimary endpoints for superiority and noninferiority trials under a unified framework. It also allows users to specify the number and timing of interim analyses to meet clinical needs. While enjoying the flexibility of Bayesian adaptive designs, the two-arm BOP2 design explicitly controls the Type I error rate and is optimal for maximizing power, thereby ensuring desirable frequentist operating characteristics. Another feature of the two-arm BOP2 design is that its decision rule can be tabulated and included in the trial protocol prior to trial commence. To conduct the trial, no complicated Bayesian calculation is needed; clinicians can simply look up the table and make go/no-go decisions. Simulation studies show that the two-arm BOP2 design has desirable operating characteristics. Easy-to-use online application is freely available at www.trialdesign.org to facilitate the use of the two-arm BOP2 design in clinical trials.