In the search for effective COVID-19 treatments, many drugs have failed to live up to their early promise. In a recent trial, seen as an important advance, the oral antiviral drug molnupiravir halved the risk of hospital admissions and deaths from COVID-19. Medical News Today explored the evidence to see whether this optimism is justified.
A global trial, led by the pharmaceutical company Merck — known as MSD outside the United States and Canada — and Ridgeback Therapeutics, has found that the companies’ experimental antiviral drug molnupiravir reduces the risk of hospital admission or death from COVID-19 by approximately 50%.
Although this was a small-scale trial, these positive results have led to countries rushing to sign up for supplies of the drug.
In the randomized, phase 3 trial, scientists gave molnupiravir or a placebo to 775 people. All the participants had tested positive for SARS-CoV-2 infections and experienced mild to moderate COVID-19 symptoms that had begun no more than 5 days earlier.
The scientists allocated each of the 775 participants randomly to one of two groups. One group received molnupiravir and the other a placebo. The participants took the capsules twice a day for 5 days.
Of the 385 patients taking molnupiravir, 28 were admitted to a hospital, compared with 53 of those in the placebo group. Eight of the placebo group participants died, while all those receiving the antiviral were alive at the end of the 29-day study period.
Recruitment into the study has now been halted because of these overwhelmingly positive results. The manufacturer, Merck, is applying for emergency use authorization from the Food and Drug Administration (FDA).
The Singapore health ministry has signed a purchase agreement for molnupiravir, and the European Medicines Agency is considering a rolling review of the drug.
“With these compelling results, we are optimistic that molnupiravir can become an important medicine as part of the global effort to fight the pandemic.”
– Robert M. Davis, chief executive officer and president of Merck
Merck plans to produce 10 million courses of the treatment in 2021 and more in 2022.
The study results have been greeted with optimism. Prof. Tim Spector, a professor of genetic epidemiology at King’s College London, told MNT: “This is an exciting result from a randomized study of 775 patients, showing major effects in reducing severity and death from a simple pill given at the onset of infection.”
Molnupiravir belongs to a class of antivirals called mutagenic ribonucleosides. These change the viral genetic material and introduce errors to prevent replication and transcription of the viral genome.
Inside the host cell, molnupiravir is converted to molnupiravir triphosphate. When the virus tries to replicate, molnupiravir triphosphate is incorporated into the viral RNA instead of the nucleoside cytidine, causing a mutation.
The mutation stops the virus from replicatingTrusted Source. This keeps numbers of the virus in the body low and should reduce the severity of the disease.
Other drugs that interfere with viral RNA have shown potential as COVID-19 treatments. Remdesivir, an intravenously administered drug that interferes with an enzyme essential for replicating viral RNA, showed early promiseTrusted Source.
Although the FDA has granted approval to remdesivir, the World Health Organization (WHO)Trusted Source no longer recommends it as a COVID-19 treatment, due to insufficient evidence to support its use.
The advantage of molnupiravir is that, unlike all the other potential treatments so far, it is an oral tablet that a person can take outside a clinical setting. At a projected cost of around $700 per person for a 5-day course, it is also more affordable than other drugs. However, this cost is still likely to limit its use.
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