FDA authorizes Pfizer’s Covid treatment pill, the first oral antiviral drug cleared during the pandemic

Paxlovid, a Pfizer’s coronavirus disease (COVID-19) pill, is seen manufactured in Ascoli, Italy, in this undated handout photo obtained by Reuters on November 16, 2021.

Pfizer | Handout | via Reuters

The Food and Drug Administration has granted emergency authorization to Pfizer‘s Covid treatment pill, a major milestone that promises to revolutionize the fight against the virus.

Pfizer’s pill is the first oral antiviral drugs authorized by the FDA that are specifically designed to fight Covid. The authorization comes at a crucial turning point in the pandemic, as hospital systems across the U.S. have been battered by a wave of delta infections, and are now bracing for another wave of patients infected with the highly contagious omicron variant.

The drug provides a new tool in the arsenal to fight Covid. While the vaccines have proven effective in preventing severe illness from the virus, health-care providers need medications to treat the tens of millions of people in the U.S. who still have not gotten vaccinated. The pill, if delivered in time, could help alleviate strain on health-care systems during an expected wave of omicron infections.

The U.S. has purchased 10 million courses of Pfizer’s treatment, Paxlovid, in a $5 billion deal. President Joe Biden said in November that his administration is working to ensure that the treatments are free and accessible. Biden said last month that delivery would start by the New Year and continue through 2022. Pfizer CEO Albert Bourla told CNBC earlier this month the company has already shipped product to the U.S. and the pills will be available as soon as the FDA authorization comes through.

Merck has contracted with the U.S. government to supply at least 3 million courses of its pill, molnupiravir, which is still awaiting clearance, for $2.2 billion.

Pfizer’s treatment is administered in two 150 milligram tablets along with a 100 milligram tablet of an HIV drug, ritonavir, twice daily. The HIV drug helps slow the patient’s metabolism, which allows Paxlovid to remain active in the body at a higher concentration for a longer period.

Merck’s 800 milligram pill is taken every 12 hours for five days after symptom onset. The drug was developed with Ridgeback Biotherapeutics.

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Pfizer’s pill was 89% effective in preventing hospitalization, according to final clinical trial data submitted by the company to the FDA earlier this month. Though initial data showed Merck’s pill was 50% effective at preventing hospitalization, a broader trial found the pill was 30% effective at preventing hospitalizations.

Bourla has said he expects Paxlovid to remain highly effective at treating people infected with the omicron variant. The pill targets an enzyme the virus needs to replicate. Bourla said it is very difficult for the virus to mutate in a way where it doesn’t need the enzyme, called a protease.

“It’s very difficult for the virus to create a strain that can live without this protease,” Bourla told The Wall Street Journal during an interview at a conference earlier this month. “It’s not impossible. It’s very difficult.”

The vaccines, on the other hand, target the spike protein that the viruses uses to invade human cells. The spike has undergone significant mutations over the course of the pandemic, which has made it more difficult for the antibodies produced by the shots to block the virus from attaching to cells. The omicron variant, for example, has about 30 mutations on the spike.

Merck’s experimental Covid-19 treatment pill, called molnupiravir

MERCK & CO INC | via Reuters

Two-dose vaccines like Pfizer’s are still effective at preventing severe illness, according to real-world data from South Africa. And a Pfizer booster shot significantly increases that protection. However, the initial two-dose vaccination series is now only about 33% effective at preventing infection, according to the data. The pills would help treat people when they get infected.

Merck’s drug was endorsed by an FDA expert panel, the Antimicrobial Drugs Advisory Committee, in a narrow 13 to 10 vote. Though the panel backed the pill, the meeting was contentious. Several doctors expressed concerns about potential side effects from the drug as well as its possible impact on the future evolution of the virus.

Molnupirvar prompts the virus to mutate and produce errors that inhibit its ability to replicate. Dr. James Hildreth, CEO of Meharry Medical College in Nashville, Tenn.

“Even if the probability is very low, 1 in 10,000 or 100,000, that this drug would induce an escape mutant from which the vaccines we have do not cover, that could be catastrophic for the whole world actually,” Hildreth told the panel the FDA panel in November.

Panel members also grappled with whether or not pregnant women should take the pill in limited circumstances when they have severe Covid. Molnupiravir induced birth defects in animal studies. Merck never intended pregnant women to use the pill and did not include them in clinical trials.