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Encore: Infusions of antibodies used to treat COVID are being phased out


As new COVID variants rise in the U.S., antibodies are getting wiped off the list of treatments. NPR's Pien Huang explains why these infusion treatments didn't last and how scientists are searching for a new generation of antibodies that might.

PIEN HUANG, BYLINE: Over the pandemic, more than 3 million COVID patients have gotten infusions of antibodies to help keep them out of the hospital. Carl Dieffenbach, a top official with the National Institutes of Health, says that now, with new immune-evasive COVID variants, these so-called monoclonal antibody treatments are out.

CARL DIEFFENBACH: Monoclonals had their day, like the Model T or like the biplane, and now it's time to move on.

HUANG: The antibody treatments have always had a major weakness - they're easily taken out by new COVID strains. And it's a flaw that's baked into how they work. Antibodies are tiny Y-shaped proteins that float around in your blood. Derek Lowe, a chemist and blogger for the journal Science, says they look for very specific targets.

DEREK LOWE: And they're just circulating around, waiting and waiting, until they happen to bump into something that they stick to really well. And they find their soul mate, basically.

HUANG: Once they stick to their soul mate - in this case, the SARS-CoV-2 virus - they tell the immune system to send reinforcements. Lowe says the most powerful antibodies can stop the virus in its tracks.

LOWE: 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.

HUANG: But the tip of the spike protein is a fickle soul mate. It changes as the virus mutates, leaving the antibodies adrift in the bloodstream with nowhere to bind. Companies have stopped bringing these antibody treatments to market because they cost millions of dollars to develop, and they're obsolete in a matter of months. So researchers are changing gears to look for antibodies that could last. Joshua Tan is head of the antibody biology unit at the NIH. He showed me around his lab in Rockville, Md.

JOSHUA TAN: This will actually orient the tour 'cause I'm going to sort of walk you through the different steps that we have.

HUANG: He and the researchers that work with him are taking immune cells from the blood of patients that have recovered from COVID, and they're pelting them with tiny plastic pellets covered with spike proteins from different coronaviruses. Cherrelle Dacon, a postdoctoral researcher at the lab, explains.

CHERRELLE DACON: And so the spike proteins coat the surface of the beads. This is, like, seven, like, different coronaviruses. So SARS-CoV-1, CoV-2, MERS, HKU-1...

HUANG: The cells that react to several coronaviruses are reacting to a part of the spike protein that's staying the same across them. Tan says the good news is that they have found some antibodies that stick to multiple coronaviruses, and they've published results in the journal Science. But the problem that they're coming up against is that the ones that they found are not so potent. Tan says, if the old antibodies hit the virus on the nose, the new ones that he's finding kind of grab it in the armpit.

TAN: At least one of the issues appears to be that it's harder to reach those parts. They need the spike protein to shift in shape.

HUANG: It's a less direct attack, so there seems to be a trade-off between how well an antibody treatment works and how long it lasts. Tan's looking for ways around this trade-off by tweaking parts of the antibody. Luckily, as Tan and others pursue the long game, there are other treatments, like Paxlovid and remdesivir, that do still work against COVID.

Pien Huang, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

Pien Huang is a health reporter on the Science desk. She was NPR's first Reflect America Fellow, working with shows, desks and podcasts to bring more diverse voices to air and online.