The Power of Integration: How the 2-in-1 Clinical Trial Design Is Changing the Future of Drug Development

The 2-in-1 clinical trial design is an innovative approach that has gained significant attention in recent years. By combining the Phase 2 proof of concept and Phase 3 confirmatory objectives into a single study, this design provides flexibility in decision-making. If the interim data meets the pre-specified criterion and shows promise, the design allows for the addition of more sample size and expansion to a confirmatory Phase 3 study. Alternatively, if the data is less promising, the trial remains in Phase 2, and the proof of concept decision is made at the end of Phase 2. Compared to other Phase 2/3 designs, the 2-in-1 design offers several unique advantages. It allows for the use of an intermediate endpoint for interim decision-making with minimal assumptions and provides a second chance to continue development or even claim statistical significance. Consequently, the design can utilize a larger sample size at the interim stage and employ a more effective boundary for risk mitigation compared to other traditional approaches for a certain given timepoint. This chapter provides a comprehensive review of the 2-in-1 design, including different versions that incorporate dose finding, group sequential design, or sample size re-estimation. It also covers various aspects related to the design, such as handling bias in estimation, choosing an intermediate endpoint, and addressing Type I error control if there is a desire to seek accelerated approval. Most importantly, the chapter discusses how the 2-in-1 design is revolutionizing drug development by increasing efficiency and minimizing risk. Additionally, the chapter explores how the design can fit into the regulatory environment, including FDA initiatives such as Project Optimus and Project Frontrunner.