A new pill from Merck has raised hopes that it could transform the landscape of treatment options for Americans at high risk of severe disease at a time when the Omicron variant of the coronaviruses is driving a surge of cases in European countries.
The F.D.A. is still considering the application of the drug maker. Regulators are wondering if the drug can cause human genes to be altered, as it wreaks havoc on the virus's genes.
The drug could affect a fetus's dividing cells, which could cause birth defects. The members of the F.D.A. expert committee expressed their concerns at the public meeting.
Do we want to reduce the risk for the mother by 30 percent while exposing the embryo and the fetus to a much higher risk of harm by this drug? The president of Meharry Medical College spoke at the meeting. There is no circumstance in which I would advise a pregnant woman to take this drug.
The F.D.A. advisers noted that the risks could extend to other patients, including men wanting to become fathers, though those risks remain poorly understood.
molnupiravir is expected to work against Omicron. It has been shown to reduce the risk of hospitalization and death by 30 percent if given within five days of symptoms emerging.
Scientists know how the drug works.
When the drug is processed in the body, it creates compounds that are very similar to the genetic material inside the coronaviruses.
The drug compound can slip into the virus's RNA and cause problems, as it can make copies of itself.
Elizabeth Campbell, an expert in structural biology at the Rockefeller University who studies coronaviruses, said in an interview that molnupiravir disguises itself. Errors can be spread all over the genome.
The virus eventually stops making mistakes, according to Dr. Campbell. It helps the body fight off the infections and possibly save the patient's life.
The problem is that the same compound can be turned into a building block of DNA. Some scientists are concerned about the possibility of errors in a patient's own genetic material.
If cells are replicating, that means they are incorporating a version of the DNA building blocks derived from molnupiravir.
A team of researchers at the University of North Carolina studied the use of molnupiravir in isolated hamster cells and found that the drug caused changes in the DNA.
The authors of that study wrote that those mutations could cause birth defects or cancer in a developing fetus or in sperm precursor cells.
The drug only targets dividing cells in adults. That poses a smaller risk than other mutagens, like radiation, which can damage cells.
Ronald Swanstrom, a researcher at the University of North Carolina at Chapel Hill who helped lead the hamster cell study, said that adults have enough dividing cells in bones and the gut to cause concern. He noted that men were making sperm cells that could carry potential defects.
Dr. Swanstrom said that nobody knows what this dose means in terms of human outcomes. I hope it is trivial, but I don't think anyone knows.
In a letter objecting to Dr. Swanstrom's conclusions, the scientists from the company said that hamster cells were exposed to the drug for much longer than Covid patients. The company said that it tested the drug in rodents and found no signs of genetic changes.
Dr. Roy Baynes, the chief medical officer at Merck, said that the molecule was low in risk for mutagenicity. The goal is to eradicate the virus quickly, and this is not a long-term treatment.
The short course of treatment lowered the risks, but Brianne Barker, a Biologist at Drew University, said that the data should be published. She said that it was difficult to know how serious the dangers would be in people because the isolated hamster cells were a bit different from the cells in an organisms.
Cells in a fetus are dividing all the time. pregnant and breastfeeding women, as well as women likely to become pregnant, were excluded from the clinical trial.
Human development in the womb is an amazing sequence of events, said Dr. John Mellors, an infectious disease specialist at the University of Pittsburgh Medical Center. You can end up with a disaster if you start tinkering with that.
According to Dr. Mellors, the drug could cause problems in pregnant rats, including the death of a fetus.
The pill should not be given to pregnant or breastfeeding women in Britain. They advised women to use contraceptives while taking the drug and for four days after.
If I were pregnant, I wouldn't take this. I wouldn't give it to a child, a teenager, or anyone whose cells are still dividing and differentiating at higher rates.
Scientists said that older pills taught them how to safely prescribe molnupiravir. Doctors used a pill called ribavirin before the advent of powerful drugs to treat hepatitis C patients.
ribavirin should not be given to pregnant women or to their male partners, and should be avoided during treatment, according to the F.D.A.
If you read the label, you will know that it is not a good idea to take molnupiravir. We didn't avoid using it because we thought, let's wait for something better.
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There is an updated list of potential treatments.
The New York Times has an interactive section onronavirusesdrugstreatments.html.
Pfizer is expected to get the government's approval for its own Covid pill within weeks, which is expected to be more effective than the one from Merck.
The country may be facing a new surge of cases caused by the Omicron variant, and molnupiravir is expected to be more readily available than Pfizer's drug in the coming months.
We have to do what we can with what we have.
The benefits of the drug could outweigh the risks for people who are at higher risk of getting sick from a coronaviruses. Adults are willing to accept an increased risk from being in the sun.
She said that the risk of Covid disease might outweigh the risk of mutagenesis in some individuals. A younger individual who is planning to have kids or a younger individual who is pregnant might want to take a different drug.
Dr. Swanstrom said he had wrestled with whether to speak up about the drug's potential to save lives, given that it is largely theoretical.
He asked if it was better to subvert this concern and hope for the best. Is it better to be open about the concerns and try to figure out what the path forward should be and have some kind of consensus around that?
It would be a bad mistake to not give the risk a chance.
Scientists want the full findings of the studies to be made public.
The long-term health outcomes of people who receive molnupiravir should be studied by researchers. The data could show whether people who take the drug develop cancer or have children with birth defects at higher rates than would be expected.
The F.D.A. advisory committee was told that the company would create a program to monitor pregnant women who take molnupiravir. Women may take the drug before they know they are pregnant if the drug is not formally authorized.
While vaccination is the most effective way of reducing Covid risks, it is not the most effective way of addressing the later stages of the Pandemic.
The entire population will never be completely vaccined, the immune responses will fade with time, and people will get infections if not here, said a professor who has studied molnupiravir.
The stakes are high for future epidemics. There is a chance that molnupiravir can work against a number of other viruses. Scientists said that there were signs that the drug would need to be used at higher doses against other viruses, making it all the more urgent to understand the risks.
Dr. Swanstrom said that this could be used against the next epidemic. We need to find out what it means to use this drug for a long time.
Rebecca Robbins was involved in reporting.
