Trending Clinical Topic: COVID Antiviral Drug

Ryan Syrek


October 15, 2021

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Promising interim results for an oral COVID-19 antiviral drug, along with news about other treatments currently used and in development, resulted in this week's top trending clinical topic.

In a phase 3 trial, Merck & Co's experimental medication, molnupiravir, was effective against all known coronavirus variants, including Delta. An interim analysis of 775 patients found that 7.3% of those who received the medication were either hospitalized or died within 29 days of treatment, compared with 14.1% of patients who received placebo. No deaths were reported in the molnupiravir group, with eight deaths in the placebo group (see the Infographic below).

Outside monitors recommended that the trial be stopped early owing to the positive results. Merck and partner Ridgeback Biotherapeutics plan to seek emergency use authorization from the US Food and Drug Administration (FDA) as soon as possible and also intend to submit applications to worldwide regulatory agencies.

Unlike all currently available COVID-19 vaccines, molnupiravir does not target the spike protein of the virus. Instead, it targets the viral polymerase, an enzyme needed for the virus to copy itself. The drug introduces errors into the genetic code of the virus. Researchers say this is what allows molnupiravir to be equally effective against current and future variants. Data show the drug is most effective when given early in the course of infection.

Pfizer Inc has launched a study into their own investigational antiviral drug for the prevention of COVID-19 among persons exposed to the virus. Pfizer will study the protease inhibitor, PF-07321332, in as many as 2660 healthy adult participants who live in the same household with an individual who has confirmed, symptomatic COVID-19 infection. It will test the drug against a low dose of ritonavir, an older medication widely used in combination treatments for HIV infection.

Experts believe that a daily pill to treat COVID may be only months away, with molnupiravir the obvious top contender. Beyond Pfizer's protease inhibitor, an antiviral produced by Roche and Atea pharmaceuticals, AT-527, is also potentially on the horizon. The need to develop antiviral therapies such as these despite the availability of a vaccine remains high, according to scientists working on a patent-free COVID treatment. Given that pharmaceutical companies retain exclusive intellectual property over their products, and owing to infrastructure challenges, most poor countries won't be widely vaccinated for another 3 years.

In terms of drugs currently being used to fight COVID, a phase 3 trial found that remdesivir cut some patients' risk for hospitalization or all-cause death by 87%. The randomized, double-blind, placebo-controlled trial evaluated the efficacy and safety of a 3-day course of intravenous remdesivir in an analysis of 562 nonhospitalized patients at high risk for disease progression. Researchers also found an 81% reduction in risk for the composite secondary endpoint: medical visits due to COVID-19 or all-cause death by day 28. Remdesivir is the only drug currently approved by the FDA for hospitalized COVID-19 patients aged 12 years or older. However, a large trial of more than 11,000 people in 30 countries, sponsored by the World Health Organization (WHO), did not show any benefit of the drug in reducing COVID deaths. The WHO has conditionally recommended against using remdesivir in hospitalized patients, regardless of disease severity.

As the pandemic and prevention strategies continue, news about the development of COVID antiviral drugs is eagerly anticipated, leading to this week's top trending clinical topic.

Read more on investigational and other therapies for COVID-19.


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