FDA Panel Mulls Merck's Molnupiravir COVID-19 Antiviral Pill

A U.S. Food and Drug Administration advisory panel is meeting Tuesday to weigh both the safety and power of Merck's new antiviral pill in preventing severe COVID-19.

There are already two strikes against the pill: Fresh data from Merck shows that the drug, molnupiravir, isn't as effective as first reported; and FDA documents prepared for the panel meeting show the pill may pose a risk of birth defects.

Merck said Friday that final study results showed the pill reduced hospitalization and death by 30% among infected adults, which is much lower than the 50% reduction first announced by the company.

And an FDA safety review noted that animal studies suggest that high doses of the drug could trigger birth defects.

U.S. health officials have said they are considering banning the use of molnupiravir in pregnant women and are weighing other safeguards, including recommending contraceptives for some patients taking the medication, the Associated Press reported.

Why a risk of birth defects? Merck's drug disables the coronavirus by inserting tiny errors into its genetic code to stop the pathogen from reproducing. That mechanism of action has raised concerns that the drug could cause mutations in human fetuses or even spur more virulent strains of the virus.

The expert panel will vote later Tuesday on whether to recommend authorizing the drug for high-risk patients. The FDA doesn't have to follow its advisory panels' recommendations, but it is typically guided by them. The FDA may also soon approve an antiviral pill from Pfizer that appears to be significantly more powerful than Merck's pill, showing 89% efficacy in reducing hospitalizations and deaths among COVID-19 patients.

Still, given the troubling emergence of the new Omicron variant, the FDA is widely expected to authorize emergency use of molnupiravir, which is already authorized for emergency use in the United Kingdom, the AP reported.

Experiments need to be conducted to see how well the pill works at disabling the Omicron variant, but there is reason to believe they would remain effective even if the new variant can evade vaccines, The New York Times reported.

Omicron has more than 30 mutations on its so-called spike protein, and some of those mutations may make it hard for vaccine-produced antibodies to attack the virus. But Merck's antiviral pills do not target the spike protein. Instead, they weaken two proteins involved in the virus' replication machinery. Omicron carries only one mutation in each of those proteins, and neither looks as if it would stop the pills from doing their jobs, the Times reported.

In a presentation to the expert panel, Merck executive Daria Hazuda said molnupiravir's activity makes it likely to be active against any new variants.

If molnupiravir is authorized in the United States, the Biden administration has ordered enough courses of treatment, at about $700 per person, for 3.1 million people, the Times reported. The treatment is to be given within five days of the start of symptoms and is taken as 40 pills over five days.

Sources

• Associated Press

• The New York Times