Rapid incorporation of Favipiravir by the fast and permissive viral RNA polymerase complex results in SARS-CoV-2 lethal mutagenesis

Favipiravir (T-705) is an inhibitor of viral RNA-dependent-RNA-polymerases (RdRp) and clinical trials for the treatment of COVID-19 are ongoing. Here, the authors show that SARS-CoV nsp12 is the fastest known viral RdRp and they provide insights into the mechanism of action of Favipiravir, demonstrating that its antiviral effect on SARS-CoV-2 is primarily mediated through lethal mutagenesis.