New study suggests anti-COVID drug may be causing virus to mutate

Merck’s molnupiravir has been used in Israel and other countries since late 2021 to treat symptomatic patients with risk factors that could lead to hospitalization or death

Renee Ghert-Zand is the health reporter and a feature writer for The Times of Israel.

Merck's new antiviral medication molnupiravir. (Merck & Co. via AP, File)
Merck's new antiviral medication molnupiravir. (Merck & Co. via AP, File)

A new study published on Tuesday suggests that the anti-COVID drug molnupiravir may be driving mutations of the SARS-CoV-2 virus.

Produced by Merck and approved by the US Food and Drug Administration in late 2021, molnupiravir is sold under the brand name Lagevrio and has been widely used in patients at risk of developing complications following COVID infection.

Originally developed to combat influenza, molnupiravir acts by inducing errors in the SARS-CoV-2 virus’ genetic code, inhibiting its continued replication.

The study, published in the prestigious peer-reviewed Nature journal, was led by scientists at the Francis Crick Institute in London. It raises the possibility that if the treatment with the drug does not fully clear the SARS-CoV-2 infection from the body, there may be a risk of transmission of molnupiravir-associated mutations.

The researchers reviewed global sequencing databases containing more than 15 million SARS-CoV-2 genomes and identified specific mutations in sequences from 2022, the year following the introduction of molnupiravir treatment.

The mutations were identified in countries with widespread use of the drug that year, including the UK, Australia, the US, and Japan. On the other hand, countries that did not permit the use of molnupiravir, including Canada, had a lower number of these mutations in screened sequences.

Israel’s Ministry of Health announced at the beginning of January 2022 that it had approved the use of molnupiravir and had completed a purchase agreement for it. The course of treatment for one person was to cost $700.

The Merck corporate headquarters in Kenilworth, N.J. on May 1, 2018. (AP Photo/Seth Wenig, File)

The ministry explained that the drug was intended for individuals aged 18 and up with mild or moderate symptoms who have at least one risk factor for deterioration to hospitalization or death, and for whom alternative drugs (such as Pfizer’s Paxlovid) were not suitable or available.

Molnupiravir is administered in tablet form and is intended for home use within three to five days of the onset of symptoms. The medication is taken for five days. It is not meant for use as a prophylactic for COVID (intended to prevent infection) and should not be taken by pregnant or breastfeeding women.

Sheba Medical Center in Ramat Gan was the first hospital in the world to collaborate with Merck on a clinical trial of molnupiravir on COVID-19. Trials showed that the drug was successful in preventing hospitalization and death in about 30% of test subjects.

The Sheba Medical Center in Tel Hashomer, January 2, 2014. (Gideon Markowicz/Flash90)

The ultimate meaning and impact of the molnupiravir-associated mutations noted by the authors of the Nature study are not yet known.

“These results indicate that molnupiravir treatment has produced a signature mutation profile that is identifiable in sequence databases, a finding that should be considered when assessing the effects and safety of this drug,” the authors said.

“However, whether molnupiravir might alter the trajectory of variant generation or transmission is difficult to predict,” they added.

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