Much of the world's attention has been captured by the race for a coronavirus vaccine.
But the development of novel drug therapies can offer us hope too — not only for the treatment of COVID-19, but for how we might prevent it.
Last week, Victorian researchers announced they had developed a new antibody-based therapy for COVID-19 which they hope to begin testing in humans next year.
Like vaccines, antibody therapies (like the one being developed) aim to bolster the immune system's ability to recognise and neutralise the virus.
But instead of imitating the infection — so that the body's immune system learns how to fight it in the future — they're designed to fight off the virus in patients who are sick or offer short-term immunity to people who have been exposed.
"We're interested in developing antibodies that can actually block the entry of the virus into the cells and therefore stop virus infection," said Associate Professor Wai-Hong Tham from the Walter and Eliza Hall Institute.
The experimental treatment, which is made up of lab-engineered antibodies, is one of dozens of antibody therapies being developed, with several clinical trials already underway.
So how exactly do these therapies work? And if they provide protection, how long might it last?
How do antibody therapies work?
Antibodies are proteins released by the immune system that bind to foreign invaders (like viruses) and signal to the immune system to get to work, said Larisa Labzin, an immunologist at the University of Queensland.
"When our immune system responds to an infection like a virus, one of the things it does is makes loads of antibodies, and each of those antibodies is produced by a different antibody-producing cell," Dr Labzin said.
"A monoclonal antibody means it's exactly the same antibody produced by one cell."
But not all types of antibodies are created equal. Some will be better at neutralising viruses like SARS-CoV-2 (coronavirus) than others.
Unlike convalescent plasma, a treatment that takes whole plasma from a recovered person, and infuses it into another patient with the disease, monoclonal antibody therapy uses a much more targeted approach.
"The idea with [monoclonal antibody therapy] is to find exactly which antibodies bind really well to the virus and are effective at blocking the virus. Researchers can isolate those [antibodies] and then manufacture them in the lab," Dr Labzin said.
Rather than waiting for a vaccine (or the virus itself) to trigger an immune response, antibody drugs are designed to mimic the body's natural defences to disable the invading virus.
Targeting the spike protein
When it comes to developing treatments for COVID-19, researchers are focused on finding antibodies that specifically target the spike protein on the surface of the SARS-CoV-2 virus, according to Dr Tham.
"The virus spike protein is the exact protein on the virus that is used to enter human cells," she said.
It can help to think of it as a lock-and-key mechanism, according to Dr Labzin.
"If you're the virus and you're holding the key in your hand ... then an antibody that binds right at your hand is going to be more effective than something that binds to your head," she said.
"The best antibodies are the ones that bind to the spike protein at exactly the point the protein binds to the ACE-2 receptors that allow the virus to get into cells."
In Victoria, researchers have screened blood plasma of recovered COVID-19 patients for billions of antibodies (produced by SARS-CoV-2 infection) to find "the most potent ones".
Dr Pham said they've developed a treatment that involves a combination of antibodies that "gum-up" the function of the spike protein and stop it entering human cells.
This cocktail approach — of combining a few different antibody types — is designed to stop the virus becoming resistant to any particular antibody.
"By combining two different types of antibodies, you can stop the escape of viral mutations as well," Dr Pham said.
The researchers have shown success in human cells in the lab and the next step is human trials.
"We don't have a timeframe, because of paramount importance now is to make it as safe and effective as possible," Dr Pham said.
Antibodies to treat patients unable to be vaccinated
Unlike antiviral drugs being used to treat COVID-19, antibody therapies also have the potential to prevent infection from taking hold in the first place.
Even if a vaccine is made available, Dr Pham said antibody treatments could be used in people who can't get vaccinated because of age or ill health.
"In particular, in settings of elderly populations … prior to outbreak, you can deliver an antibody-based therapy to protect that population that wouldn't be able to mount an immune response [to a vaccine]," she said.
The same applies to people who are immunocompromised.
Antibody therapies could also be used to protect individuals at high-risk of infection, such as healthcare workers. However, the challenge is knowing how long this immunity would last — a question researchers are still trying to answer.
Antibody-based therapies are currently used in cancer treatments and immune disorders.
As a treatment for COVID-19, they would likely be more effective than the antivirals currently available, Dr Labzin said.
"I think the main drawback is that these antibody therapies are not cheap to make — at least not yet," she said.
"But they're definitely less expensive than they were."
In the United States, pharmaceutical companies Regeneron and Eli Lily have clinical trials for antibody treatments underway, as well as UK-based company AstraZeneca.
https://news.google.com/__i/rss/rd/articles/CBMiaWh0dHBzOi8vd3d3LmFiYy5uZXQuYXUvbmV3cy9oZWFsdGgvMjAyMC0wOC0zMS9hbnRpYm9keS10cmVhdG1lbnRzLWV4cGxhaW5lZC1jb3ZpZC0xOS1jb3JvbmF2aXJ1cy8xMjYwNzc3ONIBJ2h0dHBzOi8vYW1wLmFiYy5uZXQuYXUvYXJ0aWNsZS8xMjYwNzc3OA?oc=5
2020-08-30 23:58:00Z
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