TL2:Use of Adaptive or Group Sequential Designs in Phase 1 Studies
*Jaya Natarajan, Janssen R&D LLC 

Keywords: Adaptive design, GSD, Innovative Designs, Phase 1 studies

In the FDA draft guidance, an adaptive design (AD) clinical study is defined as one that includes a prospectively planned opportunity for modification of one or more specified aspects of the study design and hypotheses based on analysis of data (usually interim data) from subjects in the study. The major focus of the guidance is adequate and well-controlled studies where Type I error rate is rigorously controlled. In the Phase 1 area, bioequivalence (BE), and thorough QT (TQT) fall under the category of adequate and well-controlled studies. Usually, BE and TQT studies are conducted in healthy subjects using a crossover design with reasonable sample size. However, if the compound has highly variable PK characteristics, the same size required to establish BE with a power of 90% is high. In addition, due to toxicity issues and other characteristics of the compound, the study may have to be conducted in patients leading to a slower enrollment rate and longer study duration. If the drug and/or its metabolites have a long half-life, parallel group design may the right choice for a TQT study. In such situation, an adaptive or a group sequential design (GSD) with stopping rule for success and/or futility will be a good option. Sample size re-estimation using estimated CV based on the data from a first group of subjects may also help. Health Canada and EMA BE guidance allow for the use of GSD. FDA guidance does not mention adaptive designs. Limited literature is available in the use of 2-stage GSD for BE testing. 1. The questions of interest are: 1. Has your company done any Phase 1 study (especially BE or TQT) using AD or GSD? If the answer to question #1 is yes, 2. What were the study design features? Did the study design include (a) Alpha-spending; (b) stopping rules for success and/or futility; (c) Estimation of nuisance parameters only (internal pilot study; blinded or unblinded analysis); (d) Sample size re-estimation? 3. Was the study stopped early for success or failure? 4. What was the impact of AD or GSD on sample size, cost and timelines? 5. Do you use any other innovative designs in Phase 1 to reduce cost and timelines?