A panel of experts advising the Food and Drug Administration voted narrowly in favor of emergency use authorization of an antiviral pill from Merck and Ridgeback Biotherapeutics to treat COVID-19.
The vote was 13 for and 10 against authorization. The FDA isn't obligated to follow the recommendations of its advisers but typically does.
If the agency authorizes use of the drug, called molnupiravir, it would be the first oral antiviral treatment for COVID-19 that could be taken at home. A second oral medicine from Pfizer, called Paxlovid, is also being considered for authorization by the FDA.
The Merck drug is taken twice a day for five days and works by causing a cascade of disabling mutations in the SARS-CoV-2 coronavirus during replication. The drug is intended for use by people with mild to moderate illness and who are at high risk of developing severe COVID-19. It is supposed to be taken within five days of symptoms.
An interim analysis of a clinical study of the drug found that molnupiravir cut the risk of hospitalization or death in half. Among people who got the drug, 7.1% ended up in the hospital or died, compared with 14.1% who got the placebo. However, the final study analysis released Friday showed only a 30% reduction in the risk of hospitalization or death.
An FDA summary showed that in the second half of the study, patients in the group treated with the drug were more likely to be hospitalized or to die than those who got the placebo. The drug's protection against death seen in the first half of the study didn't hold up in the second half.
When asked about this discrepancy by committee chairperson Dr. Lindsey Baden, Dr. Nicholas Kartsonis, a Merck senior vice president, said, "I don't have a satisfying answer to your question."
The ability of the medicine to cause mutations beyond the virus, as seen in some lab and animal tests, raised some safety issues that were discussed at length during the daylong meeting. The possibility of birth defects weighed on the panel, and there were reservations about prescribing the drug for pregnant people. But the drug could also carry some benefits for them.
"I don't think you can ethically say it's OK to give this drug in pregnancy, obviously," said Dr. Janet Cragan of the Centers for Disease Control and Prevention during the deliberations. "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."
There were also concerns about whether the drug could cause harmful mutations in the spike protein of the virus, which is the target of COVID-19 vaccines in wide use around the world.
During the panel's discussion, John Coffin, a virologist at Tufts University, said that an elevated random mutation rate like the one seen with molnupiravir is a relatively small factor in development of viral variants of concern.
Several panelists called for additional study of the medicine in people with compromised immune systems in order to look for changes in the virus after they were treated with the drug.