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Pharmacol Ther. 2020 Feb 22:107512. doi: 10.1016/j.pharmthera.2020.107512. [Epub ahead of print]

Favipiravir, an anti-influenza drug against life-threatening RNA virus infections.

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Senri Kinran University and Department of Virology, University of Toyama, Japan. Electronic address:
Department of Microbiology, Faculty of Pharmaceutical Sciences, Hokuriku University, Japan.


Favipiravir has been developed as an anti-influenza drug and licensed as an anti-influenza drug in Japan. Additionally, favipiravir is being stockpiled for 2 million people as a countermeasure for novel influenza strains. This drug functions as a chain terminator at the site of incorporation of the viral RNA and reduces the viral load. Favipiravir cures all mice in a lethal influenza infection model, while oseltamivir fails to cure the animals. Thus, favipiravir contributes to curing animals with lethal infection. In addition to influenza, favipiravir has a broad spectrum of anti-RNA virus activities in vitro and efficacies in animal models with lethal RNA viruses and has been used for treatment of human infection with life-threatening Ebola virus, Lassa virus, rabies, and severe fever with thrombocytopenia syndrome. The best feature of favipiravir as an antiviral agent is the apparent lack of generation of favipiravir-resistant viruses. Favipiravir alone maintains its therapeutic efficacy from the first to the last patient in an influenza pandemic or an epidemic lethal RNA virus infection. Favipiravir is expected to be an important therapeutic agent for severe influenza, the next pandemic influenza strain, and other severe RNA virus infections for which standard treatments are not available.


Antiviral agent; Chain termination; Ebola; Favipiravir; Influenza; Resistant virus

Conflict of interest statement

Declaration of Competing Interest K.S. reports the receipt of consulting fees from Maruho Co., Ltd., lecture fees from Maruho Co., Ltd., MSD, and Novartis, and research funding from Maruho Co., Ltd., MSD, and Japan Blood Products Organization; all payments were sent to the institution.

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