Under Japanese law and regulatory practice, an unapproved drug may be administered, or an approved drug may be administered for unapproved indications, through certain systems, such as the “compassionate use” system and through Clinical Research (excluding clinical trials implemented under the Pharmaceuticals and Medical Devices Act (the PMD Act)).

Japan's system of compassionate use was established in 2016 pursuant to a notice of the Ministry of Health, Labour and Welfare (MHLW). Under that system, an unapproved drug that is being tested in a certain phase of a clinical trial (under the PMD Act) may be administered to a patient suffering from a disease that is not related to the indication specified in the clinical trial, provided that the requirements specified in the MHLW notice are met. Typically, these are cases where the health of the patient does not satisfy conditions for participation in the clinical trial, but the patient is suffering from a severe and potentially fatal disease that cannot be treated by existing drugs.

According to a recent report in an industry news source, remdesivir, a drug developed by Gilead Sciences as a treatment for Ebola virus disease, has been administered as a treatment for COVID-19 under the "compassionate use" system in Japan. According to a database of Japanese clinical trials and research, several clinical trials and research are being implemented or prepared, including studies related to favipiravir and remdesivir, which appear to be distinct from the reported compassionate use of remdesivir.

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