With a significant percentage of the population still resistant to the Covid-19 vaccine, several pharmaceutical companies are developing what could become the world's next attempt to curb Covid-19—a short-term, daily oral antiviral pill that could accelerate recovery and slow the spread of Covid-19.

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Antivirals are already essential treatments for other infections

While there are slight variations in how antiviral drugs work, they generally treat and prevent viral infections in people and animals, Kaiser Health News reports. These drugs can be engineered to boost the immune system and fight infection, block receptors so viruses can't enter healthy cells, or decrease the amount of active virus in the body. This in turn shortens infection time and prevents the type of dangerous immune response that can potentially cause serious illness or death.

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According to KHN, antivirals are already used to treat other viral infections, including hepatitis C and HIV. And one widely prescribed antiviral is Tamiflu, a pill that can shorten the duration of influenza and reduce the risk of hospitalization if given quickly after diagnosis.

"Oral antivirals have the potential to not only curtail the duration of one's Covid-19 syndrome, but [they] also have the potential to limit transmission to people in your household if you are sick," said Timothy Sheahan, a virologist at the University of North Carolina-Chapel Hill, who helped pioneer these therapies.

While antivirals can be effective, they aren't a perfect solution, KHN reports. One important limitation is that, for antivirals to work effectively, a patient must be diagnosed and start treatment quickly.

There is currently only 1 antiviral drug approved to treat Covid-19 (and there is mixed data)

As of right now, Gilead's remdesivir is the only antiviral drug approved to treat Covid-19. However, it is administered intravenously to hospitalized patients and is not intended for early, widespread use. 

In June, Gilead announcedthat research found that remdesivir was effective in reducing deaths in adults hospitalized with Covid-19 and shortening patients’ hospital stay. The research included three studies assessing 98,654 hospitalized patients. One of the studies found that patients treated with the drug had a 23% lower risk of death, the second found that the drug significantly reduced mortality risk, and the third—a Phase 3 clinical trial—found the drug reduced mortality risk by 54% and shortened time until discharge.

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However, according to a new study in JAMA Network Open, patients who were infected with Covid-19 last year who were given Gilead's coronavirus drug remdesivir—marketed as Veklury—stayed in the hospital longer than similar patients who did not receive it.

Promising options in the pipeline

Currently, there are three promising antiviral drug candidates under study that can be administered as pills, KHN reports.

The top contender, molnupiravir, from Merck and Ridgeback Biotherapeutics showed evidence in an early study in micethat it could prevent early Covid-19 infection. And an early trialof 202 participants last spring showed that molnupiravir rapidly reduced levels of infectious virus.

This month, Merck CEO Robert Davis added that the organization expects to see Phase 3 trial data in the next few weeks, with a tentative plan to seek FDA emergency use authorization "before year-end."

Meanwhile, Roche Holding, along with Atea Pharmaceuticals, is currently studying its antiviral Covid-19 drug, AT-527, in hospitalized patients, from which Atea officials expect to see results later this year. And Pfizer began a combined phase 2 and 3 trial of its antiviral product known as PF-07321332 Sept. 1, evaluating it in both high-risk and low-risk patients who have not been hospitalized.

According to Carl Dieffenbach, director of the division of AIDS at the National Institute of Allergy and Infectious Diseases, who is overseeing antiviral development, if the results of this research is positive and emergency use is granted for any product, "distribution could begin quickly." And this would mean Americans could soon have access to a short-term, daily orally administered medication upon diagnosis with Covid-19, KHN reports. (Aleccia, Kaiser Health News, 9/24; Grant, Wall Street Journal, 9/23; Herman, Axios, 7/15)