Favipiravir (T-705) is a broad-spectrum antiviral drug that selectively and potently inhibits the RNA-dependent RNA polymerase (RdRp) of RNA viruses. It was discovered by Toyama Chemical Co., Ltd. through screening for anti-viral activity against influenza. Favipiravir is converted intracellularly into favipiravir-RTP, an active form that inhibits RdRp activity. This mechanism allows favipiravir to target a wide range of RNA viruses, including influenza, arenaviruses, bunyaviruses, filoviruses, and others that cause severe viral hemorrhagic fevers. It is effective against both sensitive and resistant influenza strains, as well as other RNA viruses. Favipiravir has shown therapeutic potential in animal models for various RNA viral infections, including Ebola and severe fever with thrombocytopenia syndrome (SFTS). However, it has potential teratogenic effects, leading to conditional marketing approval with strict regulations. Favipiravir's unique mechanism of action, involving the incorporation into viral RNA and inhibition of viral replication, makes it a promising drug for treating RNA viral infections. Clinical studies have shown that favipiravir is well-tolerated in humans and has broad antiviral activity against various RNA viruses, including influenza, arenaviruses, bunyaviruses, and filoviruses. It is currently approved for influenza in Japan and is in advanced clinical development in the US. Favipiravir's broad-spectrum activity and safety profile make it a potential therapeutic option for treating RNA viral infections that are currently difficult to treat.Favipiravir (T-705) is a broad-spectrum antiviral drug that selectively and potently inhibits the RNA-dependent RNA polymerase (RdRp) of RNA viruses. It was discovered by Toyama Chemical Co., Ltd. through screening for anti-viral activity against influenza. Favipiravir is converted intracellularly into favipiravir-RTP, an active form that inhibits RdRp activity. This mechanism allows favipiravir to target a wide range of RNA viruses, including influenza, arenaviruses, bunyaviruses, filoviruses, and others that cause severe viral hemorrhagic fevers. It is effective against both sensitive and resistant influenza strains, as well as other RNA viruses. Favipiravir has shown therapeutic potential in animal models for various RNA viral infections, including Ebola and severe fever with thrombocytopenia syndrome (SFTS). However, it has potential teratogenic effects, leading to conditional marketing approval with strict regulations. Favipiravir's unique mechanism of action, involving the incorporation into viral RNA and inhibition of viral replication, makes it a promising drug for treating RNA viral infections. Clinical studies have shown that favipiravir is well-tolerated in humans and has broad antiviral activity against various RNA viruses, including influenza, arenaviruses, bunyaviruses, and filoviruses. It is currently approved for influenza in Japan and is in advanced clinical development in the US. Favipiravir's broad-spectrum activity and safety profile make it a potential therapeutic option for treating RNA viral infections that are currently difficult to treat.