A combination of “uniquely Australian” variants will make treating severe COVID-19 more difficult, new research suggests, with fewer drugs in the “cupboard” that are effective against new evasive strains of the virus.
Key points:
- New COVID Variants Able to Evade Evushed Monoclonal Antibody Treatment, Study Finds
- Another antibody treatment, Sotrovimab, was still effective against most variants in Australia
- Experts say treating severe COVID-19 will become more difficult as the virus evolves
A new paper led by the Kirby Institute in Sydney looked at 15 variants of COVID-19 circulating in Australia in 2022 and how successful two types of monoclonal antibodies, Evushed and Sotrovimab, were in providing protection .
Monoclonal antibodies are a key tool doctors use to treat severe COVID-19 and are especially important for severely immunocompromised patients or people who cannot be vaccinated.
The drugs were given by injection or infusion to Australian adults, pregnant women and children who were at risk of developing serious disease.
The research, which has not yet been peer-reviewed, found that Evusheld was ineffective against all variants tested.
Sotrovimab still provided some protection against most of the currently circulating variants, but with a slightly lower level of efficacy.
Kirby Institute researcher Stuart Turville, who co-authored the study, said the evasion of new Omicron variants meant there were fewer effective treatments for immunocompromised people.
“It is being taken [it] out of the therapeutic cupboard … cocktail antibodies and antibodies that have worked very well,” he said.
“At the end of the day … what’s left in the therapeutic cupboard is Sotrovimab, depending on the variant, but also Paxlovid. [an antiviral].”
Newer variants can evade treatments better
Monoclonal antibodies were once hailed as a scientific breakthrough in the effective treatment of COVID-19 patients at risk of developing severe disease.
Former US President Donald Trump was successfully treated with a cocktail of monoclonal antibodies when he became infected in 2020.
Being fully vaccinated still provides protection against serious illness and death. (Shutterstock: Cute_photos)
The treatment molecules work by binding to the spike protein of the SARS-Cov-2 virus, neutralizing the virus and helping to prevent an infection from becoming serious.
But as the virus has mutated and evolved, so have its spike proteins, meaning that some monoclonal antibodies are less likely to be able to “bind” to newer variants.
Unlike earlier years of the pandemic, where new variants of concern would quickly dominate globally, Australia now has a mix of variants that is “uniquely Australian”, Dr Turville said.
And while there are many different variants now circulating, one thing they all have in common are mutations in spike proteins that make them better able to evade antibodies.
Treatments must ‘continue to evolve’
The researchers said the large number of circulating variants would make treating severe COVID-19 more difficult in the future.
“It’s a reminder that we still need to look at this virus carefully in the context of therapeutic development. We still need to look at this virus carefully in terms of vaccination,” Dr Turville said.
“And they’re the two main arsenals in our closet, so to speak, that can reduce what we call viral load.
“I think reducing the viral load whether it’s by vaccination in the wider community, reducing the viral load in vulnerable people are the key measures we have to deal with this virus right now.”
Research showed that the variants most likely to evade monoclonal antibodies were BQ.1.1, XBB.1, BR.2.1 and XBF.
Only a very small number of cases of XBB.1.5, which circulates in large numbers in the United States, have been detected in Australia.
Although vaccines are less effective at preventing people from becoming infected with newer variants of COVID-19, the research found that being fully vaccinated still offered protection against serious illness and death.
Infectious disease physician and researcher Paul Griffin said the research highlights how treatments must continue to evolve as the virus evolves.
He also said that several antivirals, which work differently than monoclonal antibodies, were still effective in treating COVID-19.
“So Paxlovid, as well as Lagevrio and Remdesivir, are all antivirals that we can use to reduce the burden of this infection,” he told ABC News Channel.
“Part of the reason we’re in such a good position is that we have tools like antivirals, but this highlights that they also need to continue to evolve.”
Evusheld and Sotrovimab are the only monoclonal antibodies approved by the TGA for use in Australia.
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