Merck says antiviral pill effective against COVID-19, lifting hopes for first oral drug

Courtesy of Merck & Co.

An antiviral pill being developed by Merck & Co. and Ridgeback Biotherapeutics dramatically reduced the number of hospitalizations from COVID-19 in a clinical trial, a major finding that could mark a turning point in the coronavirus pandemic.

Treatment with the drug, called molnupiravir, lowered the risk of hospitalization or death by roughly 50% in study participants, who all had mild or moderate COVID-19. The results were so convincing that outside trial monitors directed Merck to stop testing after an early look at study data.

Merck plans to seek emergency authorization of molnupiravir in the U.S. “as soon as possible” and seek approvals in other countries as well, according to a statement.

“With these compelling results, we are optimistic that molnupiravir can become an important medicine as part of the global effort to fight the pandemic,” said Merck CEO Rob Davis in the statement.

Though safe and effective vaccines from Pfizer, Moderna and Johnson & Johnson are widely available in the U.S., only 56% of the population is fully vaccinated, according to data from the Centers for Disease Control and Prevention.


Infections, hospitalizations and deaths from COVID-19 rose sharply and have remained at high levels amid the spread of the delta variant, and there remains a significant need for an easy-to-take treatment than can stop infections from leading to life-threatening illness.

Synthetic antibody drugs from Regeneron, Eli Lilly and Vir Biotechnology have all been shown to keep COVID-19 patients out of the hospital, and additionally, can protect people who have been exposed to the virus from infection. But antibody drugs are limited by logistical challenges that make them difficult to administer early enough to make the greatest difference. Given via an infusion, typically in a healthcare setting, antibody drugs are also complex to make.

Oral antivirals could offer a major advantage in convenience, particularly in regions or countries with less healthcare infrastructure. Merck is at the front of a group of companies, including Pfizer, Atea Pharmaceuticals and Appili Therapeutics, that are working to develop one.

The results Merck delivered Friday show these drugs may be able to deliver on their promise. The data come from the first 775 participants in a study called MOVe-OUT. Merck enrolled people with laboratory-confirmed cases of mild-to-moderate COVID-19 who had symptoms that started within 5 days of study randomization and had at least one risk factor for developing severe disease. They then received either a course of molnupiravir or a placebo.

Results showed that 28 of 385 study participants given molnupiravir were hospitalized 29 days after treatment, compared to 53 of 377 of those who received placebo, a difference in risk of about 50%. No deaths were reported among molnupiravir-treated patients, versus eight in the placebo group.

Merck said the drug was consistently effective regardless of when symptoms began or which coronavirus variant patients had been infected with, including delta.

Importantly, side effect rates were comparable between the two groups. Merck didn’t disclose specifics, but said 12% of patients on molnupiravir and 11% of placebo recipients had drug-related adverse events. About 3% of participants on placebo dropped out of the trial due to a side effect, versus about 1% on molnupiravir.

By the time investigators decided to stop the trial, Merck had recruited more than 90% of the 1,550 study subjects it had intended to enroll, meaning more data could emerge.

The results are also a win for Merck, which has played only a supporting role during the coronavirus pandemic despite being one of the world’s top infectious disease drug developers. Merck started later than others in developing a coronavirus vaccine, and scrapped two candidates in January after lackluster results. The company later stopped work on a drug for hospitalized COVID-19 patients after regulators demanded more testing.

To date, Merck’s biggest contribution to the pandemic response has been to help make doses of Johnson & Johnson’s vaccine.

But Merck had also struck a deal with Ridgeback to co-develop molnupiravir, which the privately held biotech licensed from Emory University. The pill became a top priority after early data showed it could help patients who recently developed COVID-19 clear the virus more quickly.

Merck expects to manufacture 10 million treatment courses by the end of the year and more in 2022. The U.S. government has already bought 1.7 million courses for $1.2 billion, implying a price of $700 per treatment course. Merck has negotiated supply deals with other nations as well as contracts with generic developers to make the drug available over 100 low- and middle-income countries.

Merck is also testing molnupiravir in people who have recently been exposed to infection by a household contact. Results from that study, which will involve roughly 1,332 participants, are expected by the end of the year.


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