Use of foreign clinical data in new drug development has been more frequently discussed since the Ministry of Health and Welfare adopted the new policy. Considering medical practice, assessing pharmacokinetics profile, and conducting "bridging study" play the most important parts of accepting the foreign clinical data. In this presentation, we introduce and discuss our experiences in a triptan which is a potent and selective 5HT1B/1D/1F agonist for the treatment of acute migraine, developed in Japan.
The results of Phase I studies conducted in Japan and West revealed that the pharmacokinetic profile of this triptan in healthy Japanese adults was similar to that in healthy Westerners, but exposure in Japanese was lower than in Westerners.

In Japan, a dose-response study was designed primarily to compare the efficacy and safety of 3 different doses (20mg, 40mg and 80mg) of this triptan and placebo when given to patients suffering an acute attack of migraine, and secondarily to use results from this study to establish comparable efficacy and safety with a Western population. Then, ﾒheadache responseﾓ was commonly used as a primary endpoint between the Japanese and Western studies. The patient inclusion/exclusion criteria employed in the Japanese dose-response were also similar to those of the Western studies. As a result, 402 patients were enrolled, and for the primary objective of the study, headache response showed a statistically significant dose response. Each dose of compared with placebo was statistically significant.

For the secondary objective, it has been examined whether foreign clinical data can be extrapolated to the Japanese referring to ICH-E5 Guideline, ﾒGuidelines for Ethnic Factors in Acceptability of Foreign Clinical Dataﾓ and based on the results of Japanese dose-response study and the two western studies. It was concluded that foreign clinical data can be extrapolated to the Japanese based on the following evidences;

1. The definition and diagnosis of the migraine and its therapy are considered to be similar between Japan and foreign countries.
   
   
2. For the efficacy, in all of the Japanese and the two Western studies, there was a significant dose-response in headache response at 2 hours post-dose, the primary efficacy endpoint, and the headache response were statistically significantly higher compared with that of placebo group. The magnitude of headache response in each dose in the Japanese dose-response study was similar to that in the two Western studies.
   
   
3. For the safety, the profile of adverse events observed in the Japanese dose-response study was similar to those in the two western studies.

These findings suggest that it is important to evaluate the effects of differences on the clinical efficacy and safety and to provide the scientific evidences on bridging the data, if any ethnic differences are observed.