FDA Advisory Committee Narrowly Backs Merck’s Oral COVID-19 Antiviral

The 13-10 vote was not without controversy as panel members discussed concerns over the novel antiviral's safety risks and modest efficacy.

A US Food and Drug Administration (FDA) advisory committee voted 13-10 to recommend the investigational oral antiviral molnupiravir (Merck, Ridgeback Biotherapeutics) for adults at high risk for progressing to severe COVID-19.

While the Antimicrobial Drugs Advisory Committee (AMDAC) was largely split, the panel ultimately voted that the known and potential benefits of molnupiravir outweighed the risks for the treatment of mild-to-moderate COVID-19 in high-risk persons who are within 5 days of symptom onset.

Efficacy was a point of concern among panel members because of updated results from the phase 3 MOVe-OUT trial of molnupiravir that showed the novel drug was not as effective as previously thought.

Merck announced the first set of results from the phase 3 trial in October 2021, which showed a relative risk reduction of approximately 50% in the molnupiravir treatment arm; however, the most recent analysis showed a relative risk reduction of approximately 30%.

There was also considerable discussion about the safety of molnupiravir, particular among pregnant women, after preclinical studies suggested embryo-fetal toxicity among those who received the medication.

In addition, there was a lot of back and forth on the risk of drug resistance if patients do not complete the 5-day course, as well as potential mutagenicity. Ultimately, the lack of “real-world” options propelled many committee members to vote yes.

"There's a potential concern for a lack of availability for an alternative therapy for those at high-risk, perhaps considering the loss of efficacy with monoclonal antibodies with variants," said Michael Green, MD, of the University of Pittsburgh School of Medicine, who voted yes during the committee meeting of the AMDAC.

The panel noted that their decision may be temporary as other drugs in the pipeline could present better data. For example, Pfizer recently announced their novel oral COVID-19 antiviral reduced the risk of hospitalization and death by 89% in non-hospitalized high-risk adults with COVID-19.

The final decision to grant emergency use authorization to Merck for molnupiravir is now up to the FDA, and while it does not need to follow the AMDAC’s recommendation, it historically has.