Merck says its COVID-19 antiviral pill less effective in final analysis

Pharmaceutical company Merck said Friday that in a final analysis of a clinical trial, its antiviral pill reduced the risk of hospitalization and death among high-risk COVID-19 patients by 30%, down from an earlier estimate of 50%.

The lower efficacy is a disappointment for the drug, known as molnupiravir, which health officials around the world are counting on as a critical tool to save lives and reduce the burden on hospitals. It increases the importance of a similar, apparently more effective, offering from Pfizer that is also under review by the Food and Drug Administration.

A panel of advisers to the FDA is set to meet Tuesday to discuss Merck’s treatment and vote on whether to recommend authorizing it to treat high-risk COVID19 patients.

In briefing documents posted to the FDA’s website Friday, agency reviewers did not take a position on whether the drug should be authorized, although they found that the clinical trial data did not show any major safety concerns and that the drug was effective in preventing severe disease.

The reviewers said they had only become aware of the updated efficacy estimate earlier this week and were still reviewing the data. They said they could update their assessment when the panel meets Tuesday.

Merck’s initial estimate that the drug reduced hospitalization and death by 50% came from an early look at results from 775 study participants. The updated figure announced Friday came from more than 1,400. In the final analysis, the participants who received molnupiravir had a 6.8% risk of being hospitalized, and one patient died. Those who received a placebo had a 9.7% risk of being hospitalized, and nine died.

Dr. David Boulware, an infectious disease researcher at the University of Minnesota, said he expected the drug would still receive emergency authorization. If the expert committee endorses it and the FDA heeds the recommendation, the treatment could be authorized in the United States as soon as next week.

Still, Boulware said, molnupiravir will probably be deemed a lower-tier treatment, an alternative choice for people who can’t get or don’t want more effective treatments.

Monoclonal antibody drugs, which are typically administered intravenously in the United States, have been found to reduce hospitalizations and deaths by at least 70%. Pfizer’s antiviral pill, Paxlovid, which was found in a clinical trial to cut the risk of hospitalization and death by 89%, could become available within weeks.