Yes, Molnupiravir does cause supercharged viral mutation.

Proof from a new study.

A new pre-print study in medRxiv examines the claim that one of the two new drugs used to treat Covid, Molnupiravir, cause viral mutations that could spread and become new Covid variants. They prove that this is true.

In a double blind trial with 9 patients, they gave Molnupiravir to 5 and another drug that does not cause genetic mutations in the virus to 4. They found that the 5 patients who had received Molnupiravir had viable Covid mutations that could be spread in the community when they went home, because all 9 patients still tested positive for Covid at the end of their hospital stay.

I actually examined this claim in earlier this year (2022) in May and will add this article to the fact check.

This is the study:

Antiviral treatments lead to the rapid accrual of hundreds of SARS-CoV-2 mutations in immunocompromised patients Nicholas M Fountain-Jones, Robert Vanhaeften, Jan Williamson, Janelle Maskell, I-Ly Chua, Michael Charleston, Louise Cooley medRxiv 2022.12.21.22283811; doi: https://doi.org/10.1101/2022.12.21.22283811

Like all preprint studies on medRxiv, the study has a large blue disclaimer pointing out that it is a preprint and should not be used to guide clinical practice.

Here is the abstract.

Abstract

The antiviral Molnupiravir (Lageviro) is widely used across the world to treat SARS-CoV-2 infection. Molnupiravir reduces viral replication by inducing mutations throughout the genome, yet in patients that do not clear the infection, the longer-term impact of the drug on virus evolution is unclear. Here, we used a case-control approach to monitor SARS-CoV-2 genomes through time in nine immunocompromised -patients with five treated with Molnupiravir. Within days of treatment, we detected a large number of low-frequency mutations in patients and that these new mutations could persist and, in some cases, were fixed in the virus population. All patients treated with the drug accrued new mutations in the spike protein of the virus, including non-synonymous mutations that altered the amino acid sequence. Our study demonstrates that this commonly used antiviral can ‘supercharge’ viral evolution in immunocompromised patients, potentially generating new variants and prolonging the pandemic.

This graph shows the new variants produced in each of the Molnupiravir patients A,B,C, D and E (to the right, under “Variants”; this is not seen in the non-Molnupiravir patients C1-C4.

Their conclusion is quite damning:

These data highlight the risk of treating immunocompromised patients with error generating antivirals such as Molnupiravir. All of the individuals in our study remained persistently PCR positive post-treatment, although active monitoring for clearance was not undertaken by the institution. It is possible they were infectious in the hospital and in their communities, and onward transmission of these highly divergent viruses is likely. This commonly used class of antivirals has the capability to supercharge SARS-CoV- 2 evolution, and uncontrolled use may generate new variants with a transmission advantage that prolongs the pandemic and makes other therapeutics less effective.

Here is my original fact check on this subject, which has been confirmed by this study:

Claim: Molnupiravir works by randomising the virus's genetic code

By the way belated h/t to Igor Chudov who first reported on this study

Study Confirms that Molnupiravir Creates COVID "Variant Soup". How could the FDA Approve It?