UK becomes first country to approve Merck's COVID-19 pill. British health secretary touts treatment as a 'game-changer.'

The U.K. has become the first country to approve Merck's new antiviral pill that is a treatment for COVID-19. The drug molnupiravir — which is to be branded as Lagevrio in Britain — is being lauded as a "game-changer" by the U.K.'s health secretary.

The U.K.'s Medicines and Healthcare products Regulatory Agency granted authorization for molnupiravir on Thursday. Molnupiravir has been authorized for use in adults age 18 and older who have tested positive for COVID-19 and have at least one risk factor for developing severe disease, such as obesity, heart disease, or are over the age of 60.

The COVID-19 pill developed jointly by Ridgeback Biotherapeutics and Merck works by interfering with the virus' replication. The drug is said to prevent SARS-CoV-2 from multiplying, which keeps virus levels low in the body and reduces the severity of the disease.

"Molnupiravir (MK-4482, EIDD-2801) is an investigational, orally administered form of a potent ribonucleoside analog that inhibits the replication of SARS-CoV-2, the causative agent of COVID-19," Merck's press release stated.

The British government says, "Based on the clinical trial data, Lagevrio is most effective when taken during the early stages of infection and so the MHRA recommends its use as soon as possible following a positive COVID-19 test and within five days of symptoms onset."

Molnupiravir was initially studied as a potential flu therapy that received funding from the U.S. Department of Defense and the National Institutes of Health.

"Last year, researchers at Emory University decided to repurpose the drug as a potential COVID-19 treatment," ABC News reported. "They then licensed the drug to Ridgeback and partner Merck."

The U.K.'s Health Secretary Sajid Javid said, "Today is a historic day for our country, as the UK is now the first country in the world to approve an antiviral that can be taken at home for COVID-19."

Javid added, "This will be a game-changer for the most vulnerable and the immunosuppressed, who will soon be able to receive the ground-breaking treatment."

The MHRA's chief executive, Dr. June Raine, said, "Following a rigorous review of the data by our expert scientists and clinicians, we are satisfied that Lagevrio is safe and effective for those at risk of developing severe COVID-19 disease and have granted its approval."

There was no timetable as to the release of Lagevrio in the U.K., but Javid said the "NHS to set out plans to deploy molnupiravir to patients through a national study as soon as possible."

In October, U.K. officials announced they secured 480,000 courses of molnupiravir after clinical trials by Merck and Ridgeback Biotherapeutics showed patients who received molnupiravir within five days of COVID-19 symptoms had about a 50% decrease in the rate of hospitalization and death as patients. None of the study participants had been vaccinated.

Molnupiravir is also pending review with regulators in the U.S. and the European Union.

The Antimicrobial Drugs Advisory Committee, a U.S. Food and Drug Administration advisory committee, is scheduled to "discuss the available data supporting the use of molnupiravir to treat mild-to-moderate coronavirus disease 2019 (COVID-19) in adults who have tested positive for COVID-19" on Nov. 30.

Merck reportedly has a contract to supply the U.S. government with 1.7 million courses of molnupiravir at a price of $700 per course. A review by Harvard University and King's College London estimated the drug costs approximately $18 to make.

Merck CEO Robert Davis told CNBC last week that the drugmaker is "on pace to have 10 million courses ready before the end of this year, and more than double that next year."