Molnupiravir and Paxlovid - new antivirals fight Omicron and may prevent Covid

Molnupiravir can be offered to the most vulnerable NHS Covid patients from tomorrow – with possible use in care home outbreaks

The first groundbreaking pill to fight the Sars-CoV-2 coronavirus should be able to tackle the Omicron variant – and there are encouraging signs it could work as a prophylactic drug to prevent infections, says the Antivirals Taskforce chair Eddie Gray.

From Thursday, people who test positive for Covid and are at highest risk of serious illness are eligible for molnupiravir, a new antiviral drug made by the US firm MSD in partnership with Ridgeback Biotherapeutics, which Gray believes “will be an important part of the response” to Omicron.

The genetic method the pill uses to stop the Sars-CoV-2 virus spreading in the body early in an infection means “we have every reason to believe it will retain the same level of efficacy” against the more transmissible variant, said Mr Gray. He became chair of the Government’s Antivirals Taskforce in May, charged with identifying and supporting the development of new drugs for the NHS this winter, and was speaking to i for a long read about the challenges and lifesaving benefits of antiviral drugs.

Trials show that molnupiravir reduces hospitalisations by 30 percent among unvaccinated people with Covid. Critics say this rate is disappointing, and studies on Omicron are yet to be conducted. However, Mr Gray is confident that “we might beat the 30 per cent level quite easily” when the pill is taken by the most vulnerable patients, such as those who have cancer or are immunocompromised.

Other antivirals are also causing excitement. On Tuesday, Pfizer confirmed its Paxlovid pill reduced hospitalisations and deaths by 89 per cent in trials, and was effective against Omicron. The firm said it was in “very advanced regulatory dialogue” in the UK for the pill to be approved.

Professor Chris Butler of Oxford University, who is leading the nationwide Panoramic trial of molnupiravir to see how it benefits different types of people, told i that if it eventually proves able to reduce hospital admissions even by 2 or 3 per cent, that would be a “massive” help for the overstretched NHS.

So far, the Government has bought 480,000 courses of the MSD pills and 250,000 of Pfizer’s drug. But Professor Butler said “rigorous” testing will be needed before they are made widely available, to check on the severity of side effects, monitor viral resistance, and learn how they can be used most effectively.

Mr Gray said there were early indications that both could eventually be used prophylactically, meaning they could be used in a precautionary way to stop people becoming infected in the first place, or fight a potential infection as early as possible.

This would allow residents in care homes where outbreaks are detected to be given the drugs before receiving a positive test, for example. Wider use to control infections among large parts of the population may even prove viable.

Mr Gray said that MSD and Pfizer have both started tests on prophylactic use. “They’re interested – and I think it is likely that we’ll see some efficacy,” he said. “Might we, when we’re in endemic situation, look at moving towards prophylaxis? Possibly.”

The downside of using antivirals more widely, especially just one drug on its own, is that this increases the risk of a mutation making the virus resistant. Professor Butler said: “We’ve got a big enough problem as it is with antibiotic resistance. We’ve got to be cautious.”

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