Molnupiravir, an antiviral that's moving into the final stages of testing in humans is a promising drug that can be used both to treat and prevent COVID. Importantly, it can be taken as a pill - meaning people wouldn't need to be hospitalised to receive it.

This drug reduces the ability of SARS-CoV-2, the virus that causes COVID, to replicate. It works by mimicking one of the building blocks of the virus's genetic material. When the virus reproduces, it builds a new copy of its RNA, and the drug ends up being incorporated into it.

When the virus then reproduces, the molnupiravir causes mutations to accumulate in the virus's RNA, which increase every time it replicates. Eventually, this causes an "error catastrophe", where excessive mutations stop the virus from being able to reproduce altogether, and it dies off.


So far, a small trial has looked at the effects of molnupiravir in 202 COVID patients (not in hospital) who had started having symptoms. Participants were randomly allocated to receive molnupiravir or a placebo, with different doses of the antiviral being tested.

The trial's results have been published as a preprint, meaning they are yet to be formally reviewed by other scientists. Still, the trial showed that after three days of treatment, infectious SARS-CoV-2 virus was found significantly less often in participants taking 800mg of molnupiravir (2%) compared to those taking a placebo (17%).

By day five, the virus was not detected in any participants receiving 400mg or 800mg of molnupiravir, but was still found in 11% of those taking a placebo. The trial, therefore, suggests that molnupiravir can reduce and eliminate infectious SARS-CoV-2 in patients with mild COVID. Indeed, it's the fact that molnupiravir speeds up the clearance of the virus that suggests it could be useful not just for treating COVID but also lessening the chance of it spreading.