Favipiravir shows anti-influenza virus activities with IC50 ranged from 0.013 to 0.48 μg/ml for the influenza A viruses, from 0.039 to 0.089 μg/ml for the influenza B viruses, and from 0.030 to 0.057 μg/ml for the influenza C viruses. In mammalian cell lines (MDCK cells, Vero cells, HEL cells, A549 cells, HeLa cells, and HEp-2 cells), Favipiravir shows no cytotoxicity at concentrations up to 1,000 μg/ml. In MDCK cells inoculated with seasonal influenza A (H1N1) viruses, Favipiravir induces lethal mutagenesis.
In vivo
In influenza virus-infected mice, Favipiravir (200 mg/kg/day, p.o.) protects the mice from death from influenza virus infection. In mice experimentally infected with Ebola virus, Favipiravir efficiently blocks viral production, reaching an antiviral effectiveness of 95% and 99.6% at 2 and 6days after initiation of treatment, respectively.
