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A pill to treat COVID-19 at home may soon be available. Drugmaker Merck announced on Friday that its antiviral drug, molnupiravir, cut the risk of hospitalization and death in sick individuals by half.

A convenient drug that can be taken at home could transform the fight against the coronavirus by helping people recover faster and keeping them out of the hospital. Current treatments for the virus, which include antibody drugs and the antiviral remdesivir, need to be given via an IV infusion in a hospital or clinic, and supplies have been strained by the latest wave of the Delta variant.

Similar to Tamiflu, the antiviral pill for influenza, molnupiravir would be taken twice a day for five consecutive days.

How does the COVID antiviral pill work?

Antivirals are meant to ease symptoms and shorten the duration of a viral infection. They work by interfering with a virus’s ability to replicate and spread within the body.

“If you had a metaphorical wrench to throw into the gears of this virus’s replication, you could jam up the ability of the virus to have exponential spread,” explains Ashwin Balagopal, an infectious disease physician at Johns Hopkins University and principal investigator for an ongoing trial testing the safety and efficacy of molnupiravir in hospitalized patients.

Molnupiravir introduces errors in the genome of the coronavirus when it tries to make copies of itself. Essentially, it corrupts the virus’s genetic code. Prior to the COVID-19 pandemic, molnupiravir was being studied as a potential treatment for flu.

How effective is it?

In Merck’s trial, the drug reduced the risk of hospitalization and death in individuals with COVID-19 by about 50%. In those who received molnupiravir, 7% were hospitalized, and none died. In the group that got a placebo, 14% were hospitalized, and eight people died. The Phase III study involved 775 people with a laboratory-confirmed case of COVID-19 who had at least one risk factor for severe disease, including obesity or older age.

The drug appeared effective against at least three variants, including Delta. Merck announced the findings in an Oct. 1 press release. Full data is forthcoming.

Who will be eligible to get the pill?

Molnupiravir is intended to treat people with a mild or moderate case of COVID-19 at home. In Merck’s Phase III trial, all participants began taking the pill within the first five days of symptoms. While the drug is also being studied in hospitalized patients, scientists think the earlier people are treated with the pill, the better.

“The goal of an oral antiviral is that you can shorten the course of illness by treating people early, preventing them from having to go to the hospital, and potentially subduing the disease early on for millions of people,” Balagopal says.

Individuals with COVID symptoms will likely need a positive test result in order to get a prescription from their doctor.

Are there any side effects?

Some side effects occurred in both groups in the Phase III trial, but they were more common among those who received a placebo, which means they were likely the result of COVID-19 and not the drug. Researchers will continue to study the drug in participants. In results from an early-stage trial of molnupiravir published earlier this year, the drug was found to be safe and well tolerated.

When will the pill be available?

Molnupiravir is still being studied in clinical trials and has not yet gotten regulatory approval. Merck plans to seek approval from the U.S. Food and Drug Administration soon to make the pill available to Americans. The company expects to produce 10 million courses of treatment by the end of 2021, with more doses coming in 2022. The U.S. government has already ordered 1.7 million courses of the drug. A handful of other antiviral pills for COVID-19 are also being studied in clinical trials, including ones from Atea Pharmaceuticals and Roche, as well as Pfizer.