As described in the news “国際共同治験前の日本人P１ 海外先行品は原則実施不要 薬物動態は可能な限り収集を 厚労省・薬事検討会 | ニュース | ミクスOnline (mixonline.jp)” released by MixOnline on 14/Sep/2023, Ministry of Health, Labor and Welfare will issue a new notice regarding Japanese phase 1 study soon. According to the discussion about the new notice, for drugs primarily developed overseas, there would be no need to conduct additional Japanese phase 1 study before participating multi-regional clinical trials (MRCTs) as long as the safety and tolerability risks for Japanese subjects can be explained and managed. However, it is desirable to collect as much information on the pharmacokinetics in the Japanese population as possible. In the past, Japan’s regulations, initially set in 2007, mandated phase 1 trials for Japanese participants. Many sponsors were concerned about the risk of subsequent additional trial requests, and some of them had even abandoned development. The new notification aims to minimize these obstacles and encourage international collaboration. Of particular interest is if Japan’s participation in MRCTs is possible for orphan drugs and pediatric medicines without conducting any Japanese phase 1 trial. However, not all drugs fit this criterion, decisions will be made on a case-by-case basis depending on the type and characteristics of the drug, especially for drugs with anticipated significant safety concerns. This new notice will potentially bring substantial changes to the pharmaceutical industry in Japan. With easier participation in multinational clinical trials, new drug development and market introduction are expected to proceed more smoothly in Japan.