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Drug study brings animal-to-human organ transplants a step closer, scientists say

Scientists say they are closer to understanding the best way to make the human body receptive to an organ donation from another species, an effort that could help solve an ongoing shortage of organs.

More than 100,000 people in the US are on the transplant waiting list, and an average of 17 die every day while waiting. Doctors have spent decades experimenting with alternatives, and many now see potential in replacing failing human organs with genetically modified pig organs.

Xenotransplantation, as cross-species organ transplantation is called, is still in the early stages. There are no human clinical trials taking place that have been approved by the US Food and Drug Administration, but the researchers behind a study published Thursday in the Journal of Clinical Investigation say their findings might bring human trials even closer.

For the study, doctors at the University of Alabama-Birmingham’s Marnix E. Heersink School of Medicine transplanted genetically modified pig kidneys into three people who were brain-dead and showed that they could do so using the same FDA-approved drugs used in human-to-human donations.

With any kind of transplant, whether from a human or an animal, doctors have to give the recipient medications that suppress their immune system so their body doesn’t reject the unfamiliar organ. In some cases, when patients are particularly vulnerable to infection, they might get additional therapy to offer protection from encapsulated bacteria like Neisseria meningitidis, the germ that causes meningitis.

The researchers behind the new study compared results from two pig kidney recipients who got the standard immune-suppressing drugs and an additional FDA-approved therapy called eculizumab with results from someone who got only the immune suppression drugs. The combination appeared to work best.

The study showed that doctors didn’t need to use specialty or experimental drugs for this transplant process, which would make it easier to get the work into FDA-approved human trials, said study author Dr. Jayme Locke, a professor of surgery and director of the Division of Transplantation at the Heersink School of Medicine.

“When we move this into the living, the scientist in me thinks the best way to do this is that we should change only one thing at a time, and so in this case, the only thing that we will have to change and have to be different is the organ source,” she said.

Keeping things as similar and as simple as possible would also make the process generalizable, Locke said.

“Doing this using medications that transplanters across the globe know how to use, when you start thinking about scaling this up and being able to offer this to as many people as possible, that’s also very appealing,” she added. “It just decreases the complexity of what you’re trying to do.”

The new research is limited because it was demonstrated in only three patients. As with any science, the advance shows a stepwise progression, but doctors who work on research involving transplants complimented the team for what transplant surgeon Dr. Sheri Krams called “extraordinarily innovative work.”

What the paper adds to the body of knowledge is “somewhat incremental,” said Krams, senior associate dean of graduate education and postdoctoral affairs and a professor of surgery at Stanford Medicine, who did not work on the new research – particularly compared with a study published in August that showed how to test this kind of procedure in a model using brain-dead donors, what UAB calls the Parsons Model after the first person in the study whom Locke and her team transplanted with a modified pig organ in 2021. But Krams agreed that “anything we do in transplant is great.”

Dr. Mandy Ford, scientific director of the Emory Transplant Center, agreed that the extreme need for organs makes any advance in this area important.

“There’s a critical donor organ shortage in the United States and worldwide, and xenotransplantation really has the potential to be a revolutionary permanent solution to the problem,” said Ford, who did not work on the new study but characterized it as a “major advance.”

“Using this FDA-approved regimen, I think, gets us closer to the clinical reality of being able to start clinical trials and one step closer to making xenotransplantation a clinical reality,” Ford added.

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