ABSTRACT
For marketing approval of a new drug product, the FDA requires that at least two adequate and well-controlled clinical trials be conducted to provide substantial evidence regarding the effectiveness of the drug product under investigation (FDA, 1988). However, under certain circumstances, the FDA Modernization Act (FDAMA) of 1997 includes a provision (Section 115 of FDAMA) to allow data from one adequate and wellcontrolled clinical trial investigation and confirmatory evidence to establish effectiveness for risk/benefit assessment of drug and biological candidates for approval. The purpose of requiring at least two clinical studies is not only to assure the reproducibility but also to provide valuable information regarding generalizability. Reproducibility is referred to as whether the clinical results are reproducible from location (e.g., study site) to location within the same region or from region to region, while generalizability is referred to as whether the clinical results can be generalized to other similar patient populations within the same region or from region to region. When the sponsor of a newly developed or approved drug product is interested in getting the drug product into the marketplace from one region (e.g., where the drug product is developed and approved) to another region, it is a concern that differences in ethnic factors could alter the efficacy and safety of the drug product in the new region. As a result, it is recommended that a bridging study be conducted to generate a limited amount of clinical data in the new region in order to extrapolate the clinical data between the two regions (ICH, 1998a).
