Although the "drug lag"-namely, the delay in drug approval time in Japan relative to the United States and/or European Union (US/EU)-has been shortened for drugs approved in Japan, there remain many new drugs that have been approved in the US/EU, but not in Japan. To assess the possibility of a future drug lag, this study has examined the current lag in drug development in Japan based on "ClinicalTrials.gov" data from multiregional clinical trials (MRCTs) conducted in the US/EU and East Asia. Among 828 MRCTs registered as of April 5th, 2021, the percentage of MRCTs in which Japan participated (jMRCTs) was 57.1%. jMRCTs were common for some diseases such as "nervous system" and "visual system" disorders, but less common for "neoplasm," infection," "mental," and "circulatory" disorders. Regarding the investigational drugs in non-jMRCTs (i.e., MRCTs without Japanese participation) in the latter four therapeutic areas (i.e., neoplasm, infection, mental and circulatory disorders), approximately 80% (313/399) of drugs were not being developed in Japan. Furthermore, many of these drugs were being developed by the top 50 pharmaceutical companies by sales, and the majority would be recognized as a new active ingredient with a new mode of action in Japan. This study has highlighted the possibility of a future drug lag in Japan, especially in the therapeutic areas of neoplasm, infection, mental, and circulatory disorders. Such a lag may arise not only between Japan and the US/EU, but also between Japan and other countries in the East Asian region.
Keywords: Drug lag; East Asia; Multiregional clinical trial (MRCT); Simultaneous drug development.
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