ABOVE: Merck research facility in San Francisco                                © ISTOCK.COM, JASONDOIY

Update (December 23): The US Food and Drug Administration today issued an emergency use authorization for Merck’s oral antiviral drug molnupiravir for non-severe COVID-19 disease cases in high-risk adults when no alternative treatments are available.

Update (November 29): Results of Merck's study of its molnupiravir pill show lower efficacy in reducing hospitalization risk than previously reported by the company, important considerations for the FDA advisory panel meeting this week on the drug's approval, according to STAT.

Update (November 4): The UK’s Medicines and Healthcare products Regulatory Agency announced today it has approved molnupiravir, making the country the first in the world to green light the pill.

Update (October 27): Merck has granted a license to more than 100 low- and middle-income countries to manufacture and sell its molnupiravir pill in a deal with the UN Medicines Patent Pool to increase accessibility to the medication, the company announced today.

Update (October 25): Merck has asked for approval of its molnupiravir pill from the European Medicines Agency, initiating a rolling review process as a step toward formal market authorization, the company announced today.

Update (October 11): Merck applied to the US Food and Drug Administration for emergency use of its antiviral pill today. The application specifies that the pill would be authorized only for high-risk adults such as the elderly or those who are immunocompromised, The New York Times reports.

Merck and Ridgeback Therapeutics announced today (October 1) that their oral drug molnupiravir cuts the risk of COVID-19–related hospitalization or death by 50 percent when administered within five days of the onset of COVID-19 symptoms. According to the companies’ news release, about 7 percent of the 385 trial participants who received the oral molnupiravir pill were hospitalized, and none died. The risk doubled among the 377 patients given a placebo, with about 14 percent hospitalized, and eight deaths. The data from the trials has not yet been peer-reviewed.

Merck will apply to the US Food and Drug Administration (FDA) for emergency use authorization for the drug “as soon as possible,” the announcement says.

Molnupiravir creates errors in the genetic material of the virus, thus impeding its ability to replicate. Patients in the trial took four pills twice daily for five days, The New York Times reports.

According to STAT, the way the drug is administered sets it apart from other COVID-19 therapeutics. Monoclonal antibody treatments are currently limited to high-risk populations, such as the elderly or immune-compromised, and are administered via injection or infusions. Another drug, remdesivir, must be given intravenously and is only available for hospitalized patients. Merck’s molnupiravir, in contrast, can be taken orally by outpatients. Virologist Angela Rasmussen of the University of Saskatchewan tells the Times that there could be “an objectively larger number of lives saved potentially with this drug” compared to other available COVID-19 treatments. 

Experts also expect molnupiravir to be cheaper than other COVID-19 drugs, making it more accessible than, for example, monoclonal antibody treatments, which can cost several thousand dollars per patient, according to the Times. If the drug is approved, Merck says it plans to use a tiered pricing framework for molnupiravir to account for different countries’ healthcare resources. Natalie Dean, an infectious disease researcher and biostatistics professor at Emory University, tells STAT, “The more accessible that can be, the more effective it can be.”

Merck had initially aimed to collect data on 1,500 participants in the trial, but halted early on the recommendation of an independent advisory board and the FDA due to its positive indicators of efficacy. The companies have not yet released information on what types of potential side effects the pill might have, but state in their news release that rates of adverse events in the treatment and placebo group were comparable. The Washington Post reports that animal experiments using molnupiravir indicate it is effective against variants such as Delta.

If it receives emergency use authorization, the pill could become the first clinically available oral antiviral treatment for COVID-19. Merck says it is seeking authorization from international regulators as well as the FDA. Meanwhile, competitors such as Atea Pharmaceuticals, Roche, and Pfizer are developing their own oral antiviral medications.