Monoclonal antibodies were once the star of COVID-19 outpatient treatments. Since they first became available in 2020 – even before the first vaccines – more than 3.5 million infusions of the factory-grown proteins have been given to patients in the U.S. to help reduce risk of hospitalization. But one by one, different monoclonal treatments have lost their efficacy against new variants of the coronavirus. The rise of Paxlovid antiviral pills earlier this year, further dented their appeal. Now, a new wave of omicron subvariants that are the best yet at evading the immune system’s current defenses have taken over in the U.S. They’re expected to knock out bebtelovimab, the last monoclonal antibody treatment standing against the coronavirus. Soon, it’ll join bamlanivimab, casirivimab, sotrovimab and others in the graveyard of monoclonals that once targeted past COVID strains until they were outflanked by variants that evaded their protection.
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“There are severely immunosuppressed patients that are not likely to mount an immune response to the virus, even if you treat them with antiviral drugs,” says Dr. Raymund Razonable, an infectious disease specialist in the transplant division at the Mayo Clinic. “This is the group that is going to be the most affected by the absence of antibody-based therapies.” What’s more new research is underway to develop new types of monoclonal antibodies that could even hold up against new variants.
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Monoclonal antibodies are lab-grown proteins that supplement your body’s immune system – which, in most people, is naturally producing antibodies to hunt for possible threats all the time.
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The tiny, Y-shaped proteins lurk in the blood in low concentrations, “waiting and waiting until they happen to bump into something that they stick to really well, and they find their soulmate, basically,” Lowe explains. That “soulmate” is an antigen – a foreign substance that’s entered the bloodstream, like a bacterial protein or a virus or a pollen grain. Once a monoclonal antibody finds its soulmate — in the case of COVID, a specific part at the tip of the SARS-CoV-2 virus – it binds to the surface of the antigen. Then, it sends out signals to the immune system, “like hey, I’ve got a live one,” Lowe says. The most powerful antibodies can stop the virus in its tracks just by binding to it. For instance, “if you have an antibody that sticks to the tip of the spike protein at the business end of the virus – just the fact that it is stuck tightly to that means the virus cannot infect a cell,” says Lowe.
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Companies have stopped bringing these monoclonals to market. The federal government stopped promising to buy them in quantity, making it a riskier bet for companies.
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To be clear, these are antibody treatments for outpatient treatment. There is a different kind of monoclonal antibody treatment for hospitalized patients that remains viable. Actemra, as it’s called, is not susceptible to virus mutation because it targets the body’s immune reaction to the virus, rather than the virus itself.
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And the research on and rapid development of antibody treatments has opened up possibilities beyond COVID. “It has improved the production of monoclonals for cancer, for immunologic diseases,” says Dieffenbach, “It’s going to be easier to produce monoclonals in the future because of the lessons learned from SARS-CoV-2. Nothing was wasted here.”
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Article URL : https://www.npr.org/sections/health-shots/2022/11/20/1137892932/monoclonal-antibodies-covid-treatment