The COVID-19 pandemic is caused by the coronavirus SARS-CoV-2. Drugs for the treatment of this disease are urgently needed. The antiviral compound EIDD-2801 (also called molnupiravir or MK-4482, pictured) is a potential drug candidate against COVID-19 and is currently in phase II/III clinical trials. The drug has been repurposed—originally, it was designed as a ribonucleoside analogue inhibitor of influenza viruses.

Richard K. Plemper, Georgia State University, Atlanta, USA, and colleagues have found that EIDD-2801 can reduce the viral load in the upper respiratory tract and suppress virus transmission in ferrets. The team considers ferrets a good model because the animals can readily spread the virus, but generally do not develop severe disease—similar to young human adults. The team infected ferrets with SARS-CoV-2 and started treatment with EIDD-2801 when the animals began to shed virus from the nose. The infected, treated animals were co-housed with healthy, untreated ferrets in the same cage. None of these contact animals became infected. In a control experiment, all contacts of infected, untreated ferrets became infected.

In contrast to other possible COVID-19 treatments such as remdesivir or convalescent serum, EIDD-2801 can be given orally. This could significantly simplify treatment and transmission prevention. According to the researchers, the drug could possibly help to prevent widespread community transmission of COVID-19 until vaccinations are widely available.

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• Therapeutically administered ribonucleoside analogue MK-4482/EIDD-2801 blocks SARS-CoV-2 transmission in ferrets,
  Robert M. Cox, Josef D. Wolf, Richard K. Plemper,
  Nat. Microbiol. 2020.
  https://doi.org/10.1038/s41564-020-00835-2

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