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FDA authorizes a 2nd easy-to-use COVID treatment, Merck's antiviral pill

ARI SHAPIRO, HOST:

As the number of COVID-19 cases around the country continues to climb, keeping people out of the hospital is crucial to avoid overwhelming the health care system. Today, the Food and Drug Administration issued an emergency use authorization for a second therapy that should help with that. Joining us to talk about this drug and how it might help is NPR science correspondent Joe Palca. Hey, Joe.

JOE PALCA, BYLINE: Hey, there.

SHAPIRO: We were just talking yesterday about a pill for treating COVID-19 made by Pfizer. So who makes the drug that was authorized today, and how is it different from the Pfizer drug?

PALCA: Well, this drug is made by the pharmaceutical company Merck, and it's called molnupiravir. The Pfizer drug Paxlovid disrupts the action of a key viral enzyme called protease. Molnupiravir works by disrupting the way the virus copies its genetic material. And if the virus can't copy its genetic material properly, it can't replicate and spread throughout the body of someone who's infected. The FDA authorization says it can be used in patients 18 and older who have mild to moderate COVID symptoms and who are at risk for progressing to severe COVID, either because of their age or some underlying health condition. The drug should be used as soon as COVID symptoms appear and no more than five days after the symptoms appear.

SHAPIRO: Does this Merck drug work as well as the Pfizer drug?

PALCA: Well, the short answer is no. The Pfizer drug Paxlovid reduced the risk of hospitalization and death by nearly 90% in a large clinical study of that drug. A similar study of molnupiravir only reduced the risk of hospitalization by around 30%, although it did do well at preventing deaths from COVID. Nick Kartsonis is senior vice president of clinical research for infectious diseases and vaccines at Merck. He says they tested molnupiravir in some 1,400 volunteers with COVID-19 symptoms. Half got the drug, half a placebo. Kartsonis says there were 10 deaths in the study.

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NICK KARTSONIS: Nine of them occurred in placebo, and only one occurred on molnupiravir. So when you do a relative risk reduction, it's approximately 90%.

SHAPIRO: That sounds good. But if the Merck drug reduced the risk of hospitalization by 30% and the Pfizer drug had a 90% reduction, why wouldn't doctors just give the Pfizer drug to everyone who needs to be treated?

PALCA: A couple of reasons - John Farley is with the FDA Office of Infectious Diseases. He described a couple of the reasons during a teleconference earlier today.

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JOHN FARLEY: Paxlovid interacts with other medicines that can lead to serious or life-threatening adverse reactions.

PALCA: And finally, he says, some of these medicines are in fairly common use, like some anti-cancer drugs or some heart medications.

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FARLEY: Paxlovid also is not recommended for patients with severe kidney problems or for patients with severe cirrhosis of the liver.

PALCA: And to be clear, molnupiravir has some drawbacks as well. Pregnant women shouldn't take it because of a possible harm to the fetus, and people younger than 18 aren't supposed to take it because it can interfere with bone and cartilage growth.

SHAPIRO: Still, it sounds like if you don't have those conditions and you're not taking those certain medications, then Paxlovid's the way to go.

PALCA: Well, yes, maybe. But there's one other consideration, and that's availability. The Department of Health and Human Services announced today that there were only about 65,000 treatment courses of Paxlovid available for the entire country. And there are more infections than that every day, so the supply is limited for now. On the other hand, Merck says the picture is better for molnupiravir. Here's Merck vice president again, Nick Kartsonis.

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KARTSONIS: We're going to have hundreds of thousands of courses within the next few days and a million courses within the next few weeks.

PALCA: I should add that Pfizer does expect they'll be having supplies in the millions or even tens of millions in the new year.

SHAPIRO: These drugs were obviously tested before the omicron variant came on the scene. Any evidence of how they'll work for people infected with omicron?

PALCA: Well, there's a theoretical reason to think they'll work because the omicron virus did not change the protease molecule that the Paxlovid works against or the other enzymes that the molnupiravir works against. And there are some lab tests, but they haven't been tested in humans yet. So it'll still be a while before we know that for sure.

SHAPIRO: NPR's science correspondent Joe Palca. Thank you.

PALCA: You're welcome. Transcript provided by NPR, Copyright NPR.