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Merck's Covid-19 pill

A pill is seen with Merck's logo and the words "Molnupiravir" and "Covid-19" displayed on a screen in the background on November 5, 2021. (Photo: Jakub Porzycki/NurPhoto via Getty Images)

Experts Warn Merck's FDA-Authorized Covid Pill Could 'Create Breeding Ground for Mutant Viruses'

"The FDA and Merck have essentially engaged the public in a gamble without public debate," argues Stanford University's Michael Lin.

Jake Johnson

Merck's anti-viral coronavirus pill has been heralded as a "gamechanger" in the fight against the deadly global pandemic, and the Food and Drug Administration decided last week to authorize the treatment on an emergency-use basis for certain segments of the U.S. population.

"We are potentially headed towards a world-class disaster."

But public health experts in recent days have increasingly sounded alarm over the potential drawbacks of molnupiravir, including the frightening possibility that it could—in the words of one researcher—"create a breeding ground for mutant viruses," thereby prolonging the pandemic and adding to its grisly death toll.

"The problem with molnupiravir lies in its mechanism of action," Michael Lin, associate professor of neurobiology and bioengineering at Stanford University, wrote in a recent op-ed for the Washington Post. "Unlike any previous antiviral drug, molnupiravir does only one thing: It introduces mutations into the viral genome."

Lin noted that while "we are already familiar with the fact that viruses naturally mutate to evade immunity... molnupiravir relies on inducing even more mutations so that eventually the virus' proteins are damaged beyond function. That molnupiravir can mutate SARS-CoV-2 to death has been demonstrated in the controlled conditions of a petri dish and lab animal cages, leading Merck to test it in covid-19 patients in clinical trials."

"But people are not petri dishes or lab animals, and while molnupiravir works to some extent, it has not worked very well in Covid-19 patients," Lin observed, pointing to data showing that Merck's pill has proven far less effective in preventing hospitalization than Pfizer's, which the FDA authorized for emergency use last Wednesday.

"The worst-case scenario is worrisome," he continued. "As long as molnupiravir is in use somewhere in the world, it could generate repeated cycles of new variants, with people desperately taking the drug to fight the new variants it spawns, creating a vicious positive feedback loop while causing more suffering and deaths... The FDA and Merck have essentially engaged the public in a gamble without public debate."

Lin's concerns about molnupiravir's capacity to generate new coronavirus variants could hardly be characterized as fringe alarmism, given the chorus of expert voices raising similar objections to the treatment.

Dissenting members of the FDA's Antimicrobial Drugs Advisory Committee—which narrowly voted last month to declare that molnupiravir's potential benefits outweigh its risks—argued during a recent meeting that "the overall benefit-risk ratio" of the drug was "unfavorable," specifically citing the treatment's "potential to drive viral mutations" and its "mutagenicity risks."

"Dismayed that the FDA has now made the worst decision in its history."

European Medicines Agency similarly warned in its detailed assessment of the drug last month that available data "raises the question whether [the] virus that emerges during treatment and/or in subjects who fail treatment with molnupiravir could harbor mutations with significant consequences for the success of other products intended for prevention or treatment of Covid-19."

William Haseltine, a virologist renowned for his work on HIV and the human genome project, implored the FDA in a November 1 blog post to be circumspect in its handling of molnupiravir due to "the drug's potential to supercharge SARS-CoV-2 mutations and unleash a more virulent variant upon the world," along with other potential side effects.

"My biggest concern with this drug is much larger than the health of any one person, it is molnupiravir's ability to introduce mutations to the virus itself that are significant enough to change how the virus functions, but not so powerful as to stop it from replicating and becoming the next dominant variant," Haseltine wrote.

"The drug's manufacturers, Merck and Ridgeback, are entering into licensing deals that would allow the drug to be made and sold widely in more than 105 countries, which means that, if approved by regulators, we will soon have very little control over the drug’s administration and dosages delivered,"  he added. "We are potentially headed towards a world-class disaster."

Despite such fears from outside experts and members of one of its own advisory panels, the FDA announced on December 23 that molnupiravir can be used "for the treatment of mild-to-moderate coronavirus disease... in adults with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe Covid-19, including hospitalization or death, and for whom alternative Covid-19 treatment options authorized by the FDA are not accessible or clinically appropriate."

The Biden administration has already purchased millions of courses of the five-day treatment at a price point far higher than the cost of production. Merck, a New Jersey-based pharmaceutical company, charged the U.S. over $700 per patient for the pills, which—according to one expert analysis—cost just $17.74 per regimen to manufacture.

Over a month before the FDA issued its emergency-use authorization, the U.K.'s medicines regulator approved molnupiravir, declaring that the drug is "safe and effective at reducing the risk of hospitalization and death in people with mild to moderate Covid-19 who are at increased risk of developing severe disease."

It was U.K. Health Secretary Sajid Javid who in November described the drug as a potential "gamechanger."

On Tuesday, India approved Merck's pill for emergency use, and the nation's health minister said the treatment will be manufactured by 13 companies.

France, however, publicly canceled its order for Merck's treatment last week, describing the company's latest trial data on the drug's efficacy as disappointing.

"The latest studies weren't good," said Olivier Veran, France's health minister.

The rush by some nations to greenlight coronavirus treatments comes in the context of a global surge in cases believed to be fueled by the heavily mutated Omicron strain, which was first detected last month in southern Africa.

In a series of tweets last week, Lin wrote that while he wants a "way out of this pandemic as much as anybody else," molnupiravir's approval and use across the globe risks imperiling rather than aiding that objective.

"Dismayed that the FDA has now made the worst decision in its history," Lin tweeted. "We cannot give up on raising awareness of the dangers of molnupiravir, and its poor efficacy. We must limit its use while we work on a worldwide campaign to reverse this."

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