‘Nail in the coffin’ for COVID: New drugs promise to change way we live with virus

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New antiviral pills for COVID-19 that take the fight directly to the virus could change the way the world lives with the pandemic – so long as they are proven to be as good as their manufacturers claim.

On Friday, Pfizer issued a press release claiming its antiviral reduced the risk of hospitalisation or death by 89 per cent for people at high risk from COVID-19. In October, Merck claimed its antiviral cut hospitalisations and deaths by half; the drug has just been approved for use in Britain.

Other competitors are not far behind.

Australia has placed an order for Merck’s COVID-19 treatment, which awaits emergency use approval in the US.Credit:AP

The drugs mark a step-change in the way we respond to the pandemic, scientists say. If they are approved, patients could be given a pill as soon as they test positive – or even earlier as a preventative.

“Vaccination will always be our first line of defence. But we’re never going to get rid of COVID,” said Associate Professor Nial Wheate, an expert in pharmaceutical science at the University of Sydney.

“We want to turn it into an endemic, rather than pandemic problem, something we live with. And these drugs will hopefully let us get to that point.”

Professor David Komander, who leads a lab studying COVID-19 antivirals at the Walter and Eliza Hall Institute, called them the “nail in the coffin for COVID-19”.

“If I get COVID despite being fully vaccinated … I know I have another wonderful option to effectively not die from it.”

On Sunday, Deputy Chief Medical Officer Dr Sonya Bennett confirmed the government was looking at options to purchase Merck’s drug if it is approved by Australia’s medical regulator. “But once that’s done, we should have that drug available.”

While the world has access to a broad range of COVID-19 vaccines – eight have been approved by the World Health Organisation – drugs that directly target the virus lag behind.

Just three such treatments have been provisionally approved by Australia’s drug regulator: monoclonal antibodies from Merck and GlaxoSmithKline and the early antiviral remdesivir – which displays such minimal effectiveness that the WHO recommends it not be used.

All three are administered via hospital injection, limiting their usefulness. Pfizer and Merck’s new antivirals are pills that can be taken at home.

A virus has a simple goal: to gain access to a human cell, take over the cell’s machinery and use it to make copies of itself. Vaccines trigger the immune system to make antibodies that stop a virus from getting inside the cell. Antivirals typically attack the virus when it is already in the cell, usually by gumming up the machinery the virus uses to copy itself.

Pfizer’s antiviral blocks the action of a key enzyme the virus uses as part of the copying process. Merck’s drug mimics a building block the virus uses to copy itself, getting incorporated in the virus’ genetic code before changing configuration, causing a mutation within the virus.

Both drugs were so successful in phase 3 trials, independent monitoring boards stopped the trials early, the companies claimed.

However, neither company has yet published their results in a peer-reviewed scientific journal. “We can’t put any value in press-release data,” said Professor Wheate. He was “excited, but cautious”.

If the drugs are approved, a key question for regulators will be the logistics of when and how to give them. Pfizer’s drug, for example, is given within three days of symptoms – meaning the drugs must be quickly shipped across the country.

The lagging development of antivirals is because research tends to be underfunded, even more so than vaccine research, said Dr Rob Grenfell, director of health and biosecurity at the CSIRO. “And they have been really challenging to develop.”

Antivirals must attack the virus while it is inside human cells. Mount too strong an attack, or block a key mechanism, and you can damage the cell itself.

Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.

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