Development of Triptans in Japan : Bridging Strategy Based on the ICH-E5 Guideline

In Japan, five new drug applications (NDAs) of triptans have been approved through a bridging strategy. They constituted the largest target disease field among 26 NDAs which had been approved through the strategy between 1999 and 2003. The bridging strategies of the drugs were classified into two major categories to be described below. One was to conduct a placebo-controlled dose-response study as a bridging study in an attempt to extrapolate the data from the pivotal foreign Phase III studies including a repeated dose study (i.e., zolmitriptan, sumatriptan succinate, and eletriptan hydrobromide). Another was to conduct a placebo-controlled Phase III study in Japan in an attempt to extrapolate the data for efficacy from a repeated dose study (i.e., sumatriptan and rizatriptan benzoate). The extrinsic ethnic factors relating to triptans did not interfere with the extrapolation of foreign clinical data in the five applications. A bridging strategy reduced the number of clinical trials and/or sample size. The accumulation of these bridging experiences indicated that foreign clinical data could be used to support the approval of triptans in Japan.