Molnupiravir drug eliminates COVID virus on third day of treatment, says study

The antiviral drug Molnupiravir succeeded in eliminating the active SARS-CoV-2 virus, which causes COVID-19, on the third day of starting the drug, according to the results of a study to be presented at Congress European Institute for Clinical Microbiology and Infectious Diseases (ECCMID).

Molnupiravir is an oral antiviral drug against coronaviruses, including SARS-CoV-2 and its worrying variants. The drug is a development of the pharmaceutical company MSD - known in the United States and Canada as Merck & Co.-, together with its partner Ridgeback Biotherapeutics.

The randomized, placebo-controlled trial confirmed the superiority of the drug molnupiravir over placebo in non-hospitalized adults with mild to moderate COVID-19 at risk of progression to severe disease, provided that they started therapy within five days of the onset of the symptoms. The results of the study were published in The New England Journal of Medicine.

A PCR test was used to determine SARS-CoV-2 viral loads from nasopharyngeal swabs collected on days one (baseline), three, five (end-of-treatment visit), 10, 15 and 29. The analysis included participants with infectious virus isolated at baseline and who had available a post-baseline SARS-CoV-2 RNA sample (n=92 molnupiravir, n=96 placebo).

The results showed that on the third day of treatment, no traces of SARS-CoV-2 were detected in any of 92 participants who received molnupiravir and had started the study with infection, compared with 21.8 per cent (20/96) of participants who received placebo. On Day 5, virus was detected in 0.0% (n=0/91) in volunteers taking molnupiravir compared to 2.2% (n=2/89) in the placebo arm. On day 10, no virus was detected in any of the patients with infectious virus at the start of the study.

“This analysis of the final virological outcome data of the study confirms previous observations demonstrating that a 5-day course of treatment with 800 mg molnupiravir twice daily results in a more rapid decrease in viral RNA and faster elimination of infections. “, explained Julie Strizki, MSD scientist and director of the study.

Molnupiravir works by preventing the coronavirus from replicating and has been shown to be effective against Delta and Omicron variants in previous studies.

In early March, the World Health Organization (WHO) recommended the antiviral drug molnupiravir for patients with non-severe cases of COVID-19, but who are at high risk of being hospitalized.

Patients at risk of hospitalization are those who are not vaccinated, the elderly, the immunocompromised or those who suffer from chronic diseases such as diabetes.

On the other hand, “young and healthy patients, including children and pregnant and lactating women” should not take the treatment, according to the WHO Guidelines Development Group, due to side effects such as bone growth retardation and stillbirth, observed in studies with animals.

According to WHO's updated COVID-19 guidance, the international health entity defines that this disease is not serious in cases with no critical infection, such as signs of pneumonia or a low level of oxygen in the blood.

In December, the U.S. Food and Drug Administration (FDA) issued an authorization for emergency use of molnupiravir for high-risk adults with mild to moderate COVID-19. A month earlier, in November, Britain had become the first country in the world to authorize emergency antiviral drugs for use in people over 18 years of age at high risk of worsening their cases of COVID-19. Australia, Japan and 12 other countries have also authorized treatment with monulpiravir.

Molnupiravir is now in the process of being submitted to global regulatory authorities for the authorization or approval of emergency use in other countries and jurisdictions, such as the European Medicines Agency (EMA) and is being studied in a Phase III trial.

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