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• Posted January 11, 2022

In Breakthrough Transplant, Man Receives Genetically Modified Pig Heart

In a medical first, doctors from the University of Maryland have implanted the heart of a genetically modified pig in a 57-year-old man facing the final stages of heart disease.

The surgical feat, known as xenotransplantation, opens the door to the possibility that more patients in dire need of heart transplants could get them.

"This was a breakthrough surgery and brings us one step closer to solving the organ shortage crisis. There are simply not enough donor human hearts available to meet the long list of potential recipients," said Dr. Bartley Griffith, who transplanted the pig heart into the patient. Griffith is professor of transplant surgery and directs the Cardiac Transplant Program at the University of Maryland Medical Center.

"We are proceeding cautiously, but we are also optimistic that this first-in-the-world surgery will provide an important new option for patients in the future," he said.

Heart health experts applauded the news.

"This medical breakthrough may help health care professionals solve the organ shortage crisis that leaves thousands each year without lifesaving heart transplants," the American Heart Association said in a statement. "About 20% of patients on the heart transplant waiting list die while waiting to receive a transplant or become too sick to be good candidates for the complex transplant procedure."

In 2019, the United States recorded the highest number of heart transplants, with 3,552 transplantations performed, the AHA noted.

The Maryland heart patient, David Bennett, is still doing well three days after the procedure was performed and will be monitored closely in the coming weeks to see if the transplant provides lifesaving benefits. He'd been deemed ineligible for a conventional heart transplant at the University of Maryland as well as at several other leading transplant centers that reviewed his medical records.

Bennett has been hospitalized and bedridden for the past six weeks. Connected to a heart-lung bypass machine to stay alive, he was deemed ineligible for an artificial heart pump due to a dangerous heart arrhythmia.

"It was either die or do this transplant. I want to live. I know it's a shot in the dark, but it's my last choice," the Maryland resident said in a medical center news release before the operation. "I look forward to getting out of bed after I recover."

Xenotransplantation could save many who are waiting for new hearts, but it carries risks that include the possibility of a deadly immune reaction to the implanted organ, doctors say. Still, pig heart valves have already been used to replace heart valves in humans for years.

In November, surgeons at NYU Langone Health transplanted a kidney from a genetically modified pig into the body of a person who had died but was on life support. They performed the same procedure in September, and last month said both procedures had been successful.

As for the latest surgery, the U.S. Food and Drug Administration gave emergency approval on New Year's eve for the novel procedure through its compassionate use program, according to the University of Maryland.

"This is the culmination of years of highly complicated research to hone this technique in animals with survival times that have reached beyond nine months," said Dr. Mohiuddin, one of the world's top experts in animal organ transplants who came to the University of Maryland five years ago and created it's Cardiac Xenotransplantation Program along with Griffith. "The successful procedure provided valuable information to help the medical community improve this potentially lifesaving method in future patients."

After the procedure was complete, the doctors used an experimental drug developed by Mohiuddin and Kiniksa Pharmaceuticals, providing it to Bennett alongside conventional anti-rejection drugs. Organs from genetically modified pigs are favored in xenotransplantation research, partly because of their physiological similarities to humans and primates.

In this particular donor pig, three genes that raise the risk of rejection were knocked out, while six human genes responsible for immune acceptance of the pig heart were inserted into the pig's genome. Lastly, one final gene in the pig was knocked out to prevent excessive growth of the pig heart tissue, the doctors said.

So far, so good.

"It's working and it looks normal. We are thrilled, but we don't know what tomorrow will bring us," Griffith told The New York Times. "This has never been done before."

More information

Visit the U.S. National Heart, Lung, and Blood Institute for more on heart transplants.