Favipiravir and severe acute respiratory syndrome coronavirus 2 in hamster model

There is a need for safe and effective antiviral molecules with which to combat COVID-19 pandemics. Recently, in vitro inhibitory activity of favipiravir against SARS-CoV-2 was reported. Here, we used a Syrian hamster model to explore the pharmacokinetics of this molecule and its in vivo efficacy against SARS-CoV-2. Results revealed that high doses (700-1400mg/kg/day) significantly reduced virus replication in the lungs accompanied by clinical alleviation of the disease. However, these high doses were associated with significant toxicity in hamsters. Favipiravir pharmacokinetics displayed non-linear increase in plasma exposure between the doses and good lung penetration. Analysis of viral genomes in vivo showed that favipiravir induced a mutagenic effect. Whilst the plasma trough concentrations observed in this study were comparable with those previously found during human clinical trials, this potential toxicity requires further investigation to assess whether a tolerable dosing regimen can be found in humans that effectively reduces virus replication.