Merck & Co Inc's COVID antiviral molnupiravir speeds up recovery but does not reduce the hospitalization or death rate in higher-risk vaccinated adults, detailed data from a large study showed on Thursday.
The drug, which prevents the virus from replicating, generated nearly $5 billion in sales for the U.S. drugmaker in the first three quarters of 2022.
Preliminary data from the study, carried out in the winter of 2021-2022 when the Omicron variant was dominant, was unveiled in October. As a result, doctors are already considering limiting molnupiravir's use, for instance, in Australia.
The latest results offer more detail and have been peer-reviewed.
The study, called PANORAMIC, compared the oral pill against standard treatment alone in people over 50 or those aged 18 and older with underlying conditions. They had been unwell with confirmed COVID for five days or fewer in the community setting.
When Merck originally tested molnupiravir, it was found 30% effective in reducing hospitalisations, but that was in unvaccinated patients.
In the latest study, led by University of Oxford researchers, nearly all of the more than 25,000 patients in the study had received at least three vaccine doses.
These results demonstrate that vaccine protection is so strong that there is no obvious benefit from the drug in terms of further reducing hospitalization and deaths, said study co-author Jonathan Van-Tam from the University of Nottingham.
The drug was, however, effective in reducing viral load and can help hasten patient recovery by roughly four days, researchers estimated based on study data.
There might be circumstances in which molnupiravir could be useful, for instance, in under-pressure health systems where it could be used to help key workers back to work quicker, said co-chief study investigator Chris Butler from the University of Oxford.
But ultimately, those benefits need to be weighed against the drug's cost, added co-chief study investigator Paul Little from the University of Southampton. The drug, which was developed with Ridgeback Biotherapeutics, is estimated to cost several hundred pounds for a five-day course.
"For the moment, I think you have to say that don't use this drug in the general population, including those at slightly higher-risk," said Little.
Extremely clinically vulnerable patients, although eligible to enroll in PANORAMIC, were encouraged to access COVID treatment directly from Britain's National Health Service, so the molnupiravir findings are less applicable to highest-risk patients, authors wrote in the medical journal Lancet.
Last month, Britain's National Institute for Health and Care Excellence (NICE) recommended against the use of molnupiravir at current prices because the cost-effectiveness estimates are higher than what it considered an acceptable use of the national health system's resources.
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