Investigations on the relationship between the designated systems for drug development and regulatory processes in Japan and those in the United States over an extended period of time are limited.

We aimed to comprehensively investigate the special regulatory pathways for approved drugs in Japan focusing on the types of drugs receiving SRPs, the benefits of SRP in terms of review periods, a comparison between Japan and the United States, and the investigation of mutual influences in obtaining SRPs in both countries over 20 years.

All drugs approved in Japan between September 1999 and December 2022, and those that underwent various special regulations based on publicly available information were investigated. A comparison between Japan and the United States was conducted using publicly available information.

In total, 2,309 drugs were approved in Japan between September1999 and December 2022, of which 819 drugs received special regulatory pathways. The number of drugs receiving special regulatory pathways increased annually, from 10 from September to December in 1999 to 90 in 2022. Anticancer drugs accounted for one-third of all drugs. Orphan drugs (432 drugs, 52.7%), expedited reviews (257 drugs, 31.4%), and priority reviews (135 drugs, 16.5%) were the most common regulatory pathways. For drugs receiving special regulatory pathways, 315 (38.5%) were approved within 6 months and 699 (85.3%) were approved within 12 months (the mean review period in Japan). Designations of priority review, expedited review, and orphan drug in Japan mutually influence the designation of these special regulatory pathways. In addition, designation of expedited review and orphan drug in Japan was influenced by designation of breakthrough therapy in the US, and expedited review in Japan was influenced by fast track in the US. In the US, special regulatory pathways are not significantly overlapped each other in the US.

In the drugs approved in Japan, the Japanese specific special regulatory pathways are mutually influenced. Expedited review and orphan drug in Japan are significantly impacted by the specific special regulatory pathways of the US. Additionally, special regulatory pathways of the US did not influence each other.