A European medical committee recommends rejection of Merck’s COVID-19 treatment, Lagevrio, casting fresh doubt on a pill that also stirs concern among U.S. regulators.

A European Medicines Agency committee says marketing authorization for the antiviral pill for use in the European Union should be refused.

A statement from the agency says a committee that has been reviewing Merck’s application for more than a year concluded that the drug’s clinical benefit could not be demonstrated.

Merck said Friday that it plans to appeal the recommendation, which came from the Committee for Medicinal Products for Human Use.

The drugmaker noted that more than two dozen countries have already approved or authorized the pill, including the United States. More than 4 million people have been treated with Lagevrio.

The United Kingdom became the first country in the world to authorize the drug in November 2021.

Merck said in a statement that it remains confident that the anti-viral pill “has an important role to play in the COVID 19 treatment landscape.”

Lagevrio and Pfizer’s pill treatment, Paxlovid, hit the U.S. market more than a year ago. They offer an easier way than IV medicines to treat patients with early COVID-19 symptoms who are at risk of serious illness.

Merck’s drug inserts tiny errors into the coronavirus’ genetic code to slow its reproduction. U.S. regulators have said it should be used cautiously.

The U.S. Food and Drug Administration authorized the treatment in late 2021 with restrictions. It cannot be used on patients under age 18. It also isn’t recommended for pregnant women because of the potential for birth defects.

The agency also has said Merck’s drug should be considered for patients “for whom alternative COVID-19 treatment options authorized by the FDA are not accessible or clinically appropriate.”

The European Medicines Agency said Merck submitted results from a study involving more than 1,400 unvaccinated adult patients. It also provided data from other studies and real-world use.

The agency said in a statement that it wasn’t possible to conclude that Lagevrio reduces the risk of hospitalization or death or shortens recovery time or illness in adults at risk of severe complications.

The FDA has said the drug is effective against the virus, but its advisory panel only narrowly endorsed the treatment. The FDA authorized it in December 2021.

Lagevrio brought in about $5.7 billion in sales last year for Merck & Co. Inc., which is based in Rahway, New Jersey. Merck makes the treatment with Ridgeback Biotherapeutics.

For 2023, Merck forecasts about $1 billion in Lagevrio sales.

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