May 25, 2022

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How Covid antiviral drugs from Merck and Pfizer work, effectiveness

Two new Covid pills are almost here — and they could be potential game-changers for ending the pandemic.

On Tuesday, Pfizer applied for approval from the U.S. Food and Drug Administration for its Paxlovid pill, meant to treat patients who are sick with Covid. Fellow drugmaker Merck asked the FDA to grant emergency authorization for its Covid pill, called molnupiravir, last month.

If the agency approves either request, treatments in the U.S. could be available before the year’s end — joining Britain, which approved molnupiravir on Nov. 4, becoming the world’s first country to do so. The FDA’s Antimicrobial Drugs Advisory Committee hasn’t released a timeline for reviewing Pfizer’s data yet, but plans to meet on Nov. 30 to discuss Merck’s data.

Once approved, the Centers for Disease Control and Prevention would then need to craft nationwide guidelines for using the drugs.

The pills come with potential concerns, including affordability for the average person. Both drugs have only been tested on high-risk individuals — like elderly people or those with underlying medical conditions like obesity or heart disease — meaning it’s unclear how they’d affect other Americans.

But they represent a potential turning point in the pandemic: the ability to easily treat sick patients, prevent severe illness, keep people out of the hospital and lower the country’s Covid death rate.

“All the excitement around these medications is warranted,” Dr. Daniel Griffin, a clinical instructor of medicine in the division of infectious disease at Columbia University Medical Center, tells CNBC Make It.

Here’s how the pills work, and what they mean for potentially ending the pandemic:

Merck’s molnupiravir 

Merck’s Covid pill isn’t exactly new: It was initially developed in the early 2000s to treat influenza.

When the pandemic hit, scientists pivoted to see if molnupiravir could work on SARS-CoV-2, the virus that causes Covid, says Dr. Judith O’Donnell, professor of infectious diseases at the Perelman School of Medicine at the University of Pennsylvania.

Once the virus enters a human cell, it duplicates its RNA to replicate and spread throughout the body. Merck’s antiviral drug mimics parts of that RNA, purposefully making mistakes in the virus’ genetic code that cause it to mutate itself into extinction.

People experience “the height of viral replication” when they first start experiencing Covid symptoms, Griffin says, meaning Merck’s pill is most effective when taken within a week of testing positive.

Patients take eight pills a day for five days — which sounds like a lot, but Merck’s most recent clinical trial is encouraging. Unvaccinated patients with mild or moderate cases of Covid who took molnupiravir within five days of developing symptoms had about a 50% reduction in hospitalization and death rates, compared to those who received a placebo pill.

Assuming the FDA approves the pill, the U.S. government plans to spend roughly $2.2 billion on enough doses of molnupiravir for 3.1 million courses of treatment, Merck announced last week.

That means each treatment costs the U.S. $700 to purchase — no small fee, but cheaper and easier to deploy than an intravenous drug like remdesivir, which costs $3,000.

“There’s already a lot of groundwork being set up so that these drugs can very quickly be distributed,” Griffin says.

Pfizer’s Paxlovid

What these drugs mean for ending the pandemic

The pills, if approved, could turn Covid into an easily treatable disease, rather than one that lands you in the hospital.

“If they can prevent hospitalization, that makes a huge difference to me here in the trenches,” O’Donnell says.

Both drugs’ trials focused on unvaccinated people, who are roughly 29 times more likely than fully vaccinated people to be hospitalized with Covid, according to a CDC study from August. If you’re fully vaccinated against Covid, you’re highly unlikely to experience severe symptoms if you get sick.

Regardless of the pills’ approval status, experts say unvaccinated people should still get vaccinated. It’s far more important to prevent infections than it is to treat the disease, Dr. Anthony Fauci said during a White House briefing last week.

Vaccines prevent transmission of the virus, which could lead to dangerous Covid mutations in the future. And while consumer pricing for the pills is currently unknown, the vaccines are free in the U.S.

The pills’ long-term risks are largely unknown at this stage. O’Donnell says she’d also like to know if the pills could be prescribed as a prophylactic for someone who’s been exposed to Covid, or if they can prevent transmission.

“Those would be wonderful things,” she says.

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