An FDA expert advisory committee narrowly signed off Tuesday on the first antiviral to treat COVID-19.
The drug, molnupiravir from Merck and Ridgeback Biotherapeutics, is intended to be used in unvaccinated people at risk for severe COVID-19 within five days of the start of symptoms. The pills, which would be available by prescription, are meant to be taken twice a day for five days.
Until now, the only treatment available to help keep people with COVID-19 out of the hospital has been monoclonal antibodies, which must be delivered by shot or infusion.
The Antimicrobial Drugs Advisory Committee, which met from 9 a.m. to 5:30 p.m. to consider drug safety and effectiveness data, voted 13 to 10 to authorize molnupiravir for emergency use during the pandemic. Committee members said the drug should not be given during pregnancy if any other alternative exists.
The FDA, which typically follows the panel’s recommendation, will make the final decision on the drug’s authorization.
The committee’s chairman Dr. Lindsey Baden, of Harvard Medical School, said the majority of members were lukewarm about the drug but voted to authorize its use because there are so few alternatives.
Several committee members said they want to reconsider authorization if an alternative becomes available.
Pfizer is developing a different antiviral, Paxlovid, which is expected to be ready for consideration in coming weeks. Early data suggests the Pfizer drug is even more effective, preventing 90% of hospitalizations in a similarly at-risk population. Less safety data is available so far on Paxlovid.
Neither drug has been tested against the omicron variant, and later trial data suggested that molnupiravir was less effective against delta than against earlier variants, though Merck said their data suggests it should have an effect against all variants.
The federal government has pre-purchased 1.7 million courses of molnupiravir for $1.2 billion, pending regulatory authorization, just over $700 per person. Pfizer has struck a deal to provide 10 million courses of Paxlovid for $5.3 billion if it is authorized, or about $530 per person.
The pre-purchase agreements mean patients would receive the drugs for free.
By comparison, Tamiflu, an antiviral against the flu, costs about $100 in the United States. Monoclonal antibodies, used to treat at-risk people at the beginning of their COVID-19 infection, costs $2,100 per use, which has been paid for so far by the federal government. Vaccines, which prevent infection, cost about $12 a dose.
Among high-risk patients, molnupiravir reduced the rate of hospitalization by nearly half compared to a placebo, according to one company study.
But some committee members said they weren’t convinced by the data and worried that more than 30 people would need to be treated with molnupiravir for one to benefit.
Committee members were uncomfortable allowing molnupiravir for pregnant women because studies in animals suggested there could be some risk to the fetus.
“There is no circumstance in which I would advise a pregnant woman to take this drug,” said Dr. James Hildreth, president and CEO of Meharry Medical College in Nashville, Tennessee. Other members said the drug should only be used if the mother was at particularly high risk from COVID-19 and monoclonal antibodies were not available.
The committee also discussed concerns about whether widespread use of the drug could lead to mutations, potentially making the virus more dangerous or less likely to be blocked by vaccines and therapies.
Members said they wanted Merck to track people who are immunocompromised as they take the drug, to ensure the virus is not mutating in dangerous ways within them. People with weakened immune systems cannot fight off the virus effectively and can be sick for extended periods of time, allowing more mutations to develop.
A number of committee members said they are concerned that monoclonal antibodies might not be effective against the omicron variant, which is so new that studies have not yet been completed.
Dr. Richard Murphy, an infectious disease physician at the VA White River Junction Medical Center in Vermont, said he wasn’t convinced that molnupiravir’s effectiveness justified its risks.
“When an alternative agent comes along with better efficacy and fewer safety concerns,” he said, this authorization “should be immediately reconsidered.”
Even members who voted for authorization expressed little enthusiasm, but noted there are few alternatives.
“I’m not sure this is the (drug) we’ve been waiting for, but it’s all we’ve got at the moment,” said John Coffin, a microbiologist at Tufts University in Boston.