A bayesian approach for evaluation of bridging studies

[[abstract]]In 1998, the International Conference on Harmonisation (ICH) published a guidance on “Ethnic Factors in the Acceptability of Foreign Clinical Data” to facilitate the registration of medicines among ICH regions including European Union, the United States, and Japan by recommending a framework for evaluating the impact of ethnic factors on a medicine’s effect such as its ef‚cacy and safety at a particular dosage and dose regimen. This guideline is known as ICH E5 guideline. As indicated in the ICH E5 guideline, a bridging study is de‚ned as a supplementary study conducted in the new region to provide pharmacodynamic or clinical data on ef‚cacy, safety, dosage, and dose regimen to allow extrapolation of the foreign clinical data to the population of the new region. Therefore, a bridging study is usually conducted in the new region only after the test product has been approved for commercial marketing in the original region based on its proven ef‚cacy and safety. Moreover, when a bridging study is conducted, the ICH E5 guideline directs the regulatory authority of the new region to assess if dose response, safety, and ef‚cacy in the new region are similar to those in the original region. However, the ICH E5 does not clearly de‚ne the similarity