Merck’s at-home antiviral COVID-19 pill approved by US regulator

United States health regulators have authorised a second antiviral pill against COVID-19, providing another easy-to-use medication to battle the rising tide of Omicron infections.

The US Food and Drug Administration authorised Merck’s molnupiravir on Thursday. The approval comes a day after the agency cleared a competing drug from Pfizer. That pill, Paxlovid, is likely to become the first-choice treatment against the virus, thanks to its superior benefits and milder side effects.

Merck’s drug was shown to reduce hospitalisations and deaths by about 30 percent in a clinical trial of high-risk individuals early in the course of the illness. The FDA authorised the oral drug for the treatment of mild-to-moderate COVID-19 in adults who are at risk for severe disease, and for whom alternative coronavirus treatments are not accessible or clinically appropriate.

Molnupiravir’s ability to head off severe COVID-19 is much smaller than initially announced and the drug label will warn of serious safety issues, including the potential for birth defects.

The Pfizer pill works differently and does not carry the same risks. Additionally, Pfizer’s drug was roughly three times more effective in testing than Merck’s, reducing hospitalisation and death by nearly 90 percent among high-risk patients.

Both the Merck and Pfizer pills could, however, be promising tools for those who are sick with COVID-19, especially in the face of the fast-spreading Omicron variant, which is now dominant in the US and beyond.

“As new variants of the virus continue to emerge, it is crucial to expand the country’s arsenal of COVID-19 therapies using emergency use authorisation,” said Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research.

Antiviral pills, including Merck’s, are expected to be effective against Omicron because they do not target the spike protein where most of the variant’s worrisome mutations reside.

Merck’s drug is not authorised for use in patients younger than 18 because molnupiravir may affect bone and cartilage growth, the FDA said. Pfizer’s drug was authorised on Wednesday for people aged 12 and older.

The US government’s contract for 10 million courses of the Pfizer drug at a price of $530 per course compares with the deal with Merck for as many as 5 million courses of molnupiravir at a price of $700 per course.

Both treatments will be free to patients in the US.

Merck’s drug inserts tiny errors into the coronavirus’s genetic code to slow its reproduction. That genetic effect has raised concerns that the drug could cause mutations in human fetuses and even spur more virulent strains of the virus. But FDA scientists said the variant risk is largely theoretical because people take the drug for such a short period of time.

Some experts question whether there will be much of a role for the Merck drug in the US.

“To the extent that there’s an ample supply of Pfizer’s pill, I think it won’t be used,” said Dr Gregory Poland of the Mayo Clinic, referring to the Merck drug. “There would be no reason, given it has less efficacy and a higher risk of side effects.”

Dr Nick Kartsonis, Merck’s senior vice president of clinical research, said the company’s scientists are still studying the drug and they hope to eventually get it approved for use in children.

The restrictions on molnupiravir were expected after an FDA advisory panel only narrowly endorsed the drug last month, warning that its use would have to be strictly tailored to patients who can benefit the most.