Potential link found between Merck antiviral and mutated COVID strains

A new study published Monday links COVID-19 antiviral created by Merck with new mutations of the virus that have been sequenced around the world.

Molnupiravir, known commercially as Lagevrio, is one of two COVID-19 antivirals authorized for treating coronavirus infections along with Paxlovid from Pfizer. The drug works by inducing mutations in the virus's cells as it replicates, resulting in random mutations that are harmful to the virus and cuts down on its viral load.

Researchers from the U.K. and South African delved into the question of where some mutated variants may have occurred, given that some have been found with seemingly random mutations, and whether molnupiravir may have contributed to the rise of some strains.

In the study published in the Nature science journal, researchers looked at available data from patients who were treated with molnupiravir and those who were not. Their findings confirmed the drug's ability to cause high rates of mutations in the virus, and they noted that a "high proportion" of these mutations are likely to be hazardous to the virus.

They also looked at sequenced COVID-19 genomes from global databases and narrowed down mutations that were only sequenced in 2022, after molnupiravir became available, and found that many of the sequences were consistent with mutations that were found in patients treated with the antiviral.

They cited a specific type of mutation that rarely occurs in natural SARS-CoV-2 evolution but which they note is induced through the use of molnupiravir. High rates of the specific mutation which researchers associated with molnupiravir use were found in populations of countries where use of the treatment was higher, such as in seniors in Australia where retirement homes were stocked with the drug.

The study put forward that molnupiravir may increase genomic diversity in the viral cells that survive the hazardous mutations brought on by the drug, expanding the variety from which SARS-CoV-2 can select from for future changes.

"Importantly, the divergence of the molnupiravir mutation spectrum from standard SARS-CoV-2 mutational dynamics might allow the virus to explore the fitness of distinctive parts of the possible genomic landscape to those it is already widely exploring in the general population," the study stated.

"Molnupiravir-induced mutation could also potentially allow infections to persist for longer by creating a more varied target for the immune system."

When reached for comment, Merck questioned the strength of the evidence presented by the researchers.

"The authors assume these mutations were associated with viral spread from molnupiravir-treated patients without documented evidence of that transmission. Instead, the authors rely on circumstantial associations between the region from which the sequence was identified and timeframe of sequence collection in countries where molnupiravir is available to draw their conclusions," said the company.

"Furthermore, these sequences were uncommon and were associated with sporadic cases. As noted by the authors, there are limitations to the analyses conducted in this study, which are described in more detail in the manuscript," Merck added. "These data must be considered in the context of all available clinical and non-clinical molnupiravir data."