Merck’s Molnupiravir Narrowly Nets FDA Panel Blessing

FDA gave emergency authorization to Merck's Molnupiravir.

FDA gave emergency authorization to Merck's Molnupiravir. (Kena Betancur/Getty Images)

Days after Merck announced that its antiviral treatment molnupiravir had a lower efficacy against COVID-19 than previously believed, the drug moved one step closer to receiving Emergency Use Authorization after a U.S. Food and Drug Administration panel narrowly gave the thumbs up.

On Tuesday, the FDA’s Antimicrobial Drugs Advisory Committee voted 13 to 10 to recommend emergency authorization of molnupiravir, which was co-developed with Ridgeback Biotherapeutics. The FDA is not required to follow the recommendations of its advisory panel but often does.

The in-favor vote came after Merck and Ridgeback announced updated results from its Phase III study. Initially, interim data announced in October showed that molnupiravir demonstrated a 50% efficacy in treating COVID-19. However, over the holiday weekend, Merck and Ridgeback provided updated results that showed molnupiravir only offered a relative risk reduction of 30%.

The reported loss of efficacy came after the United Kingdom authorized the use of molnupiravir in adults who have mild-to-moderate COVID-19 and at least one risk factor for severe disease. The two companies also came to an agreement with the government of Japan to secure approximately 1.6 million courses of molnupiravir should it receive authorization from that country’s government. They also came to a similar agreement with the U.S. government.

What is the Purpose of Molnupiravir?

Molnupiravir is an investigational, orally administered form of a potent ribonucleoside analog that is designed to inhibit the replication of SARS-CoV-2. If authorized or approved, the recommended dose for molnupiravir based on the Phase III MOVe-OUT clinical trial would be 800 mg twice daily for five days. The medication is expected to be taken within five days of the display of symptoms following exposure to the virus.

In its report on the vote, CNBC noted that many members of the advisory committee called the vote difficult, especially given the latest data provided by the companies. Also, there were concerns raised over some safety concerns, particularly in pregnant women. According to NPR, some of the panel members worried that the drug could lead to some birth defects in unborn children. Panelists also expressed concern over whether or not the use of molnupiravir could cause mutations in the spike protein of the SARS-CoV-2 virus that could be harmful, NPR added. The protein spike of the virus is the target of most vaccines and antiviral agents.

Merck and the FDA have both recommended against the use of the antiviral in pregnant women and children. In animal studies, molnupiravir was lethal to embryos in pregnant rats and caused defects in young animals it was tested on, CNBC said.

Some of the committee members also called for an additional study of molnupiravir in individuals who have compromised immune systems. This would allow researchers to look for changes in the virus after they were treated with the drug, they said.

While the FDA will begin to examine the data for Merck’s molnupiravir, Pfizer will be paying close attention to the debates for its own antiviral drug, Paxlovid. Earlier this month, the company announced plans to seek Emergency Use Authorization after an interim analysis of Phase III data revealed the medication can reduce the risk of hospitalization or death by 89% in high-risk adults who were not hospitalized for treatment.

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