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Molnupiravir: A pill for COVID-19?

A new antiviral drug is promising to reduce COVID-19 hospitalisations and deaths.

On Tuesday, the federal government announced the purchase of 300,000 doses of molnupiravir, an oral antiviral drug being tested against COVID-19 but not yet approved by the TGA as a COVID-19 treatment.

The drug, originally developed to treat influenza, is manufactured by Merck and Ridgeback Biotherapeutics and has shown promising results in a phase-3 clinical trial to treat mild to moderate COVID-19 infection.

According to a press release published by the drug manufacturers, molnupiravir reduced the risk of hospitalisation or death by approximately 50% compared to placebo in COVID-19 positive patients.

The phase-3, randomised, placebo-controlled, double-blind, multi-site study included 775 adult patients with mild to moderate COVID-19 infection confirmed by PCR testing. All participants in the study also had at least one risk factor associated with poor disease outcomes, such as obesity, older age (>60 years), diabetes mellitus, and heart disease.

Patients were randomised into two groups within five days from the appearance of symptoms. One group received the molnupiravir pill, while the second group received a placebo.

Of those who received the experimental treatment, 7.3% needed to be admitted to the hospital within 29 days, but none died. In contrast, 14.1% of patients who received the placebo were hospitalised or died within 29 days.

According to the study, molnupiravir demonstrated consistent efficacy across the most common viral variants Gamma, Delta and Mu.

“While there are a number of treatments for COVID-19 on the market, many of them are expensive, difficult to administer, not widely available, or only marginally effective,” says Dr Vinod Balasubramaniam, a virologist at the Jeffrey Cheah School of Medicine and Health Sciences at Monash University Malaysia.

“Molnupiravir could solve many of these challenges.”

The drug is administered orally twice daily for five days, while most commonly used COVID-19 treatments such as monoclonal antibodies require intravenous transfusions.

The only antiviral drug currently used against COVID-19, remdesivir, also has to be delivered directly into the bloodstream.

“A drug like molnupiravir could be especially useful because it is administered in the early stages of the disease. Since it’s just a pill, it may spare the patient a trip to a clinic for a transfusion. That reduces the chances of an infected patient transmitting the virus to medical staff, and it averts potential complications associated with transfusions,” Dr Balasubramaniam says.

But he warns the information provided by the drug manufacturers must be treated with prudence. “We have limited study information so far, although it is very encouraging,” he says.“New drugs like molnupiravir require more testing and review, but they offer the possibility of a stronger, more targeted approach.”

Encouraged by positive early results, Merck has been producing molnupiravir and expects to make 10 million courses of treatment by the end of the year and more in 2022.

The pharma company has engaged with governments worldwide, including the US and the Australian government, to arrange supply and purchase agreements for molnupiravir.

Merck has also announced that the company has entered into non-exclusive voluntary licensing agreements with generic manufacturers to make the drug easily accessible for low- and middle-income countries.

“If the results hold up to scientific scrutiny, this is very big news indeed,” Dr Vinod Balasubramaniam says.

He says vaccines remain the “ultimate shield” against the pandemic, but novel effective treatments are crucial additional tools.

“Vaccines offer long-term, robust and durable protection via immunological memory against COVID-19 before the real infection itself, training our body to be ever ready to fight this disease – something an antiviral pill could not provide,” he says. 

“Vaccination should remain the long-term priority for governments worldwide in the fight against this pandemic. But antiviral strategies such as molnupiravir should be added as part of our portfolio to fight COVID-19 and future pandemics to give a synergistic effect that will have a better outcome.”

Manuela Callari

Dr Manuela Callari is a Sydney-based freelance science writer who specialises in health and medical stories.

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