Shortly after doctors began experimenting with human pig organs, calls and emails began to arrive at New York University Langone Hospital and Massachusetts General Hospital.
People worried that they might never get a rare human transplant asked, “When will we get pig kidneys?”
Alex Berrios of Louisville, Kentucky, needs a second transplant, but finding another match has proven impossible. So he's keeping a close eye on opportunities for pig kidney research.
“It might not work out, but you have to accept that,” Berrios said. “I think it's worth a try.”
Two American companies aim to begin clinical trials of the world's first life-saving xenotransplants using pig kidneys and hearts in 2025. Potential volunteers want to know if they qualify.
Expectations rose in late November with the news that an Alabama woman underwent a pig kidney transplant at New York University and is making a smooth recovery. Twana Rooney is the fifth American to receive a gene-edited pig organ.
No two recipients of pig hearts and kidneys have ever survived more than two months, but a severe shortage of human organs available for transplantation discourages researchers from doing so. There wasn't.
“We have to have the courage to continue,” said Dr. Bartley Griffiths, a transplant surgeon at the University of Maryland.
proceed with the quest
Back in 2022, Griffiths struggled to find a way to ask a dying patient if he would consider receiving the world's first gene-edited pig heart transplant.
He was surprised to find patient David Bennett joking about begging and declaring that if his last attempt failed, “people like me might learn something.”
As far back as late 2023, patients attending a National Kidney Foundation meeting with U.S. Food and Drug Administration officials and pig developers revealed that their lives on dialysis were so miserable that they, too, decided to receive animal organs. He said it was possible.
“Why not give it a try? That's what we've really brought back,” said Mike Curtis, CEO of organ development company eGenesis. “It was as if we had an obligation to try.”
“The patients pushed us to move forward,” agreed Dr. Tatsuo Kawai, a general surgeon at a mass hospital who was initially reluctant to broach the idea. In March of this year, he administered the first gene-edited pig kidney to a longtime patient.
patient raises hand
In Palm Springs, California, Carl McNew emailed New York University to ask about volunteering while he was still fairly healthy.
McNew donated a kidney to her husband in 2015, but her remaining kidney has since failed, which is highly unusual for living donors. Medications and intermittent dialysis are helping, but McNew knows she will eventually need a transplant.
“Being part of something like that is just cutting edge,” said McNew, who came across news of New York University's xenotransplant research in 2023 and emailed him with interest.
Berrios was born in his late 20s with one kidney failing, but a living donor transplant helped him regain his health over the next 13 years. It failed in 2020 and has since developed another human kidney-destroying antibody that doctors call “highly sensitized.”
Every Monday, Wednesday and Friday, Berrios spends nearly four hours hooked up to a dialysis machine. The grueling treatment is the only way for the father of two to stay alive and hold a full-time job.
Dialysis does not completely replace kidney function, and people slowly become sicker. So Berrios told New York University that he was interested in pig kidneys, even as he tried experimental treatments to suppress the antibodies in question.
tough exam
FDA rules require that pig organs be extensively tested on monkeys and baboons before they are tested on humans. Although researchers extended the survival of these primates to a year, and in some cases longer, they longed for experience with humans.
For the first time, surgeons at New York University and the University of Alabama at Birmingham examined the organs of recently deceased pigs donated for scientific research.
The patients who have received donated pig organs so far have received “compassionate use” transplants, an experiment that the FDA allows for some emergency patients among other options.
Although the first four did not survive long due to complications from other diseases, their experiments proved that pig organs could function, at least for a while, and provided other lessons. For example, the discovery of a swine virus in the first heart transplant led to increased testing for that risk.
Only rigorous studies comparing patients with similar diseases will provide a clearer picture of the potential of pig organs. Perhaps a study like Rooney's. Despite eight years of dialysis, she was not as ill as previous xenograft recipients, but was unable to find a compatible donor. Like Berrios, she had a highly sensitized immune response.
New York University's Montgomery, who led her transplant with Alabama's first surgeon, Dr. Jamie Locke, said Rooney may be “a kind of litmus test” for trial candidates. “She got the transplant at the right time” before dialysis caused too much damage.
gene editing
Scientists have tried for years to transplant animals to humans without success, but now they have edited the genes of pigs to prevent the human immune system from immediately attacking foreign tissue. Now we can fill in the gaps. Still, no one knows the optimal combination of genes.
Revivicor, a subsidiary of United Therapeutics, manufactures kidneys and hearts using 10 gene edits to “knock out” genes in pigs that cause excessive rejection and overgrowth of organs, improving fitness. Some human genes have been added for this purpose. In Maryland, hearts with 10 gene edits were used in two xenotransplants. Rooney also received 10 gene-edited kidneys based on Locke's research while working in Alabama.
Montgomery is excited about Rooney's progress, but he accomplished most of the work using Ribibicol pigs with just one round of gene editing in a xenotransplant and decedent study last April.
“Our feeling is that less is more,” Montgomery said, noting that pigs with fewer genetic modifications are easier to mass produce. Rooney's transplant provides an opportunity to compare “how much of a difference additional gene editing really makes.”
In Boston, eGenesis uses as many as 69 gene edits. In addition to the 10 genetic modifications to improve human fitness, genes associated with certain swine viruses have also been inactivated.
eGenesis's Curtis said researchers are under pressure to prove whether pig organs can keep humans alive much longer than a few months. If not, the question becomes, “Do we have the right gene editing?”
To achieve balance, we select participants who are sick enough to qualify, but not so sick that they don't have a chance.
“So many patients are very willing, very willing, to do this,” says Silke Niederhaus of the University of Maryland, who is not involved in the xenotransplant study but is keeping a close eye on it. the doctor said.
Niederhaus became a kidney transplant surgeon because someone saved her life around her 12th birthday. That kidney lasted 30 years. When that failed, it took five years to find another one. So she understands the appeal of pig research and encourages people to find out the odds of getting a human kidney before volunteering.
If they are young and healthy or have a living donor, “I would probably say go with what is known and what is proven,” she said. But if they're older and dialysis isn't working for them, “it might be worth the risk.”
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