Favipiravir (T-705) is a novel viral RNA polymerase inhibitor, it is phosphoribosylated by cellular enzymes to its active form, Favipiravir-ribofuranosyl-5′-triphosphate (RTP). Favipiravir-RTP inhibits the influenza viral RNA-dependent RNA polymerase (RdRP) activity with IC50 of 341 nM.
Favipiravir, also known as Favilavir, T705, or Avigan, is a selective inhibitor of viral RNA-dependent RNA polymerase with activity against many RNA viruses, influenza viruses, West Nile virus, yellow fever virus, foot-and-mouth disease virus as well as other flaviviruses, arenaviruses, bunyaviruses and alphaviruses. Activity against enteroviruses and Rift Valley fever virus has also been demonstrated. The mechanism of its actions is thought to be related to the selective inhibition of viral RNA-dependent RNA polymerase. Favipiravir does not inhibit RNA or DNA synthesis in mammalian cells and is not toxic to them. In 2014, favipiravir was approved in Japan for stockpiling against influenza pandemics.