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FDA advisory panel narrowly recommends Merck’s Covid pill for emergency use

The committee voted 13-10 in favor of the drug, calling the decision "difficult."
The antiviral medication molnupiravir.
Merck and Ridgeback Biotherapeutics' antiviral medication molnupiravir. Merck & Co. via AP

A Food and Drug Administration advisory panel voted Tuesday to recommend Merck’s experimental antiviral pill to treat Covid-19 for emergency use authorization, paving the way for the agency to clear the first oral drug for the disease. 

Members of the agency’s Antimicrobial Drugs Advisory Committee voted 13-10 in favor of the treatment, called molnupiravir, for use in adults with mild to moderate Covid-19 who are at risk for severe disease or hospitalization.

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During the daylong public meeting, committee members raised numerous questions and expressed concerns about the safety and efficacy of the drug, which is made by Merck and Ridgeback Biotherapeutics, before narrowly voting in favor.

AMDAC chair Dr. Lindsey Baden said following the vote that most of the committee members appeared to fall in the middle when weighing the risks versus the benefits of the drug.

Those who voted in favor, Baden said, thought the drug's efficacy was "apparent, albeit with issues that have to be weighed." Those who voted against the recommendation, he summarized, weren't convinced by the data and cited concerns about potential risks, including potential harm to fetuses and DNA damage.

The FDA is not required to follow the advisory committee’s guidance, but it usually does. A final ruling by the agency could come in a matter of days. 

While vaccination remains the best form of protection against the virus, experts say pills like Merck’s could help stop the disease from progressing in those who do get infected and prevent hospitalization. The nation is currently averaging 5,456 Covid hospitalizations and 1,032 deaths per day, according to the Centers for Disease Control and Prevention

Clinical trial data found that the medication — which can be prescribed by a physician, picked up at a pharmacy and taken at home — reduces the risk of hospitalization and death among high-risk Covid patients by 30 percent.

That's less effective than the currently authorized monoclonal antibody treatments, which have been shown to reduce the risk of severe outcomes from Covid by at least 70 percent.

Committee member Dr. Richard Murphy, an infectious diseases physician at the White River Junction VA Medical Center in Vermont, said he would be more likely to recommend monoclonal antibodies to his patients but would consider using Merck’s drug if those treatments weren’t available. Murphy voted against recommending molnupiravir.

Despite its lower efficacy, pills like Merck’s have advantages: All other FDA-backed treatments require an IV or injection.

During a presentation to the advisory committee Tuesday, Merck’s scientists said they expect the drug will work against the new omicron variant, first identified in South Africa, as the strain contains similar mutations to other versions of the virus. Further testing is still needed, they added.  

Merck’s pill works by introducing errors, or mutations, into the virus’s genetic material, which make it difficult for the virus to replicate. 

But adding mutations to the virus could theoretically lead to new versions of the virus, a concern raised by several advisory committee members. In documents published ahead of the meeting, the FDA said the drug may increase the rate of changes in the virus’s spike protein, “which, in theory, could enhance SARS-CoV-2 spike protein evolution.” 

Patrick Harrington, a virologist at the FDA, on Tuesday presented data from a Phase 2 trial that showed changes to the spike protein were found more often in participants that received the drug, compared to those who received a placebo. 

Dr. Sean Curtis, senior vice president for global regulatory affairs and clinical safety at Merck, responded to questions raised by the committee about the potential risk of these changes, noting that in the clinical trials, no infectious virus was detected at the end of the five-day treatment course. He also said the company would emphasize the importance of taking all of the pills as prescribed.

Merck’s drug is given in four 200-milligram capsules, taken twice a day for five days, Curtis told the committee. Patients should begin treatment early, he said; in Merck’s clinical trial, participants were given the drug within five days of symptom onset. 

Initially, demand for Merck’s drug could outstrip supply, health experts say. The federal government has agreed to purchase about 3.1 million courses of molnupiravir for $2.2 billion, with the option to buy 2 million more.

Who should take molnupiravir? 

The treatment, if authorized, would be recommended for use in adults at risk of severe outcomes from Covid, such as older people and those with underlying conditions such as diabetes, obesity or heart disease. 

Committee member Dr. Uma Reddy, an obstetrician at the Yale School of Medicine asked that the FDA only authorize the drug for people who were in the clinical trial, like unvaccinated adults at risk for severe outcomes. Reddy voted in favor of the drug, though she said that pregnant women should not receive it.

Merck is recommending patients to use contraception while using the treatment and for four days after the last dose.

While both Merck’s data and the FDA’s analysis found no major safety concerns for the drug, Mark Seaton, an official at the agency’s pharmacology and toxicology division, noted potential risks to pregnant women.

Seaton cited animal studies that suggest the drug could cause harm to the fetus or possible birth defects. These risks were not observed in the clinical trials, however, because pregnant women were excluded from Merck’s study and the use of contraception was required for all participants. 

How and in what circumstances pregnant women should be allowed to take the drug was a contentious topic for the committee.

“I don’t think you can ethically say it’s OK to give this drug in pregnancy, obviously,” said committee member Dr. Janet Cragan, a medical officer at the CDC's birth defects branch who voted in favor of the drug. “But at the same time, I’m not sure you can ethically tell a pregnant woman who has Covid-19 that she can’t have the drug if she’s decided that’s what she needs.”

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Some committee members were blunt, saying there should be no circumstance where pregnant women should be given the drug.

“What it comes down to for me is, do we want to reduce the risk for the mother by 30 percent of harm by exposing the embryo and the fetus to a much higher risk of harm by this drug? And my answer is no,” said committee member Dr. James Hildreth, president and CEO of Meharry Medical College in Tennessee. Hildreth voted against recommending molnupiravir.

Robert Heflich, a scientist at the FDA’s division of genetic and molecular toxicology, said during a presentation that a byproduct of the drug was shown to induce low levels of mutations in the DNA of animal cells, suggesting it could pose a risk of cancer. 

However, Heflich noted the risk of damage to DNA in a clinical setting appears to be low, later adding the drug will likely only be given to those at the greatest risk for severe Covid. 

Possible side effects from the treatment include diarrhea, nausea or dizziness, Merck said.  

Pfizer has also applied for emergency use authorization for an oral antiviral. The FDA advisory committee is expected to review the Pfizer treatment in the coming weeks.

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