Live updates: follow the latest news on Covid-19 variant Omicron
On Tuesday, the US Food and Drug Administration approved the emergency use of Merck’s Covid-19 antiviral drug molnupiravir, with a panel assessing the drug’s trial results and voting 13 to 10 in favour of authorising its use.
There were some concerns the drug could pose a risk to pregnant women and children under the age of 18, and side effects of the pill will be closely monitored. But Tuesday’s vote represents an assessment that the benefits outweigh these risks, with the panel recommending the drug’s use for high-risk adults.
The UK approved molnupiravir on November 4, becoming the first country to do so. Australia, South Korea, Japan, Switzerland and France have joined a growing number of countries to order the drug.
But the latest data disappointed advocates of the pill.
In October, Merck’s data suggested the drug reduced the risk of hospital admission and death by about 50 per cent when patients took the pill within five days of symptoms appearing.
Dr Anthony Fauci, chief medical adviser to US President Joe Biden, said at the time that the drug could be a “game changer”, but that pills could not be a substitute for a mass vaccination campaign.
The most recent review of the drug’s effectiveness found it reduced hospital admissions and patient deaths by 30 per cent.
The drug, along with Pfizer’s Paxlovid pill, works by inhibiting an enzyme that allows the reproduction of the virus in the body.
This “mechanism of action” has given rise to the hope that the Pfizer and Merck pills will work for all variants.
Paxlovid is now under review by the FDA and Pfizer has already signed a deal with the US government to provide enough doses for 10 million people, at a cost of $5.29 billion.
Francois Balloux, director of the University College London Genetics Institute, said the way Covid pills work could actually make them more effective against variants with a high number of mutations, such as the Omicron strain.
“If anything, the Omicron variant might be more susceptible than previous Sars-CoV-2 lineages to molnupiravir given the large number of mutations it already carries in its spike protein. As such, Omicron may be more easily sent into 'mutational meltdown'," he said.
Pfizer’s early trials showed the drug was effective against Covid-19, reducing the risk of hospital admission and death by 89 per cent, based on trial results of Paxlovid in November.
Company directors at Pfizer and Merck say the pills will work on new variants, although Pfizer chief executive Albert Bourla said that although he was “very confident” Paxlovid would work on new variants, his company was looking at a back-up plan.
“We are working on other drugs for the eventual case that maybe a resistance is developed [by the virus],” he told CNBC.
Dr Nicholas Kartsonis, Merck's senior vice president for clinical research of infectious diseases and vaccines, told the FDA panel that the company was “feverishly working to collect samples” of Omicron for testing.
“If Omicron turns out to have substantial immune evasiveness, the pills will add a significant layer of defence. We should get these small molecules into mass production, especially Paxlovid, with its takedown of upstream Mpro, and much higher efficacy than molnupiravir [to date],” Eric Topol, a professor of molecular medicine at the Scripps Institute, said on Twitter on Monday.
Pfizer has said it would allow generic manufacturers to supply its pill to 95 low and middle-income countries through licensing agreements with international public health group Medicines Patent Pool.
Merck has licensing pacts for its pill in more than 100 countries, raising hope that the drugs could be vital in developing countries where health services are under intense pressure because of the low vaccination rate and a lack of critical care beds in hospitals.