US government advisers have narrowly recommended that doctors be allowed to prescribe Merck’s antiviral pill to high-risk patients, paving the way for emergency authorisation of a new Covid-19 treatment amid concerns about the Omicron variant and a recent uptick in infections.
Health experts on a US Food and Drug Administration panel voted by a margin of 13 to 10 on Tuesday to give a green light to the drug molnupiravir, which trials showed could reduce the risk of severe disease and death from Covid-19 in unvaccinated people by almost a third.
However, the advisers said the easy-to-administer treatment should only be recommended for high-risk patients over the age of 18 with mild-to-moderate symptoms. The committee urged tight restrictions on use in pregnant women because of concerns about potential side effects.
US authorities are not required to follow the recommendation from the Antimicrobial Drugs Advisory Committee, but most experts expect the FDA to swiftly authorise the drug because of concerns about Omicron, a new coronavirus variant spreading rapidly in southern Africa.
Regulators in the UK and EU, where countries are battling a fresh wave of infections ahead of winter, granted emergency use authorisation for molnupiravir this month.
Over several hours on Tuesday, the FDA committee’s members debated whether the modest benefits provided by the drug outweighed the potential safety risks.
Last week, Merck said the treatment was less effective than it had thought.
An early look at data from a large trial of the drug found it reduced hospitalisations by almost 50 per cent compared with a placebo — prompting Merck to halt the study and seek the emergency authorisation. But that figure dropped to roughly 30 per cent upon final analysis of the trial.
“I voted yes but this was clearly a very difficult decision,” said Michael Green, a member of the advisory committee and a professor at the University of Pittsburgh.
The only Covid treatments approved outside hospital settings in the US are monoclonal antibodies developed by Regeneron, Eli Lilly and GlaxoSmithKline, which are typically given via intravenous infusions.
If authorised by the FDA, doctors will be able to prescribe a five-day course of Merck’s antiviral pill to be taken at home. However, experts have noted that treatment must be administered within days of contracting Covid for it to be effective.
Earlier on Tuesday, Regeneron warned that preliminary testing suggested its treatment would be less effective in people infected with the Omicron variant. Moderna, the vaccine maker, also predicted that existing jabs would be less effective against the new strain.
Green said he had voted to recommend Merck’s drug owing to “the lack of availability of an alternative therapy for those at high risk, perhaps including the possibility and loss of efficacy of monoclonals with the emergence of variants”.
Fears over whether existing vaccines and therapies will effectively combat the variant have prompted some health experts to predict that pills such as Merck’s will play an important role in treating Omicron infections.
Pfizer has also applied for emergency use authorisation for its rival antiviral pill, which reduced hospitalisation and death by almost 90 per cent in a large trial of high-risk adults with Covid.
Unlike the vaccines and monoclonal antibodies, Merck’s pill does not target the virus spike protein. Instead, it tries to trick the virus into using the wrong building blocks, leading to mutations that cause it to form a weak chain. Pfizer’s pill blocks an enzyme that coronavirus needs to replicate.
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