A Third Person Has Received a Transplant of a Genetically Engineered Pig Kidney

A 53-year-old woman was the third to undergo the transplant procedure. Researchers are hoping to monitor the long-term effects.

An Alabama woman has become the third person to receive a kidney transplant from a genetically engineered pig, her doctors announced Tuesday.

Towana Looney, 53, is off of kidney dialysis after undergoing the procedure at NYU Langone Health on November 25. She was discharged from the hospital on December 6, and her doctors say she is in good health. Her surgery is the latest in a series of similar procedures known as xenotransplantation, the practice of transplanting organs from one species to another.

More than 103,000 people in the United States are on the waiting list for a transplant, with the vast majority of those needing a kidney. With human donor organs in short supply, some researchers are exploring the use of pigs as a potential source.

“I am overjoyed,” Looney said at a press conference Tuesday morning. “I’m blessed to have received this gift, a second chance at life.”

Earlier this year, surgeons carried out pig kidney transplants in living people for the first time. In March, 62-year-old Richard Slayman made history when he received a kidney from a genetically engineered pig at Massachusetts General Hospital. He was discharged from the hospital and was initially doing well, but he died nearly two months after the transplant. In a statement released by the hospital, his medical team said there was no indication that his death was the result of his transplant. In November, Slayman’s surgeon said his death was caused by an “unexpected cardiac event,” and there was no sign that his body had rejected the organ.

In the second attempt, this April, 54-year-old Lisa Pisano received both a kidney and thymus gland from a genetically engineered pig after getting a mechanical heart pump implanted days prior. The addition of the thymus, a small organ in the upper chest that’s part of the immune system, was meant to help prevent rejection. That surgery was also performed at NYU Langone. But 47 days after the transplant, her doctors elected to remove the pig kidney following several episodes of the heart pump not being able to pass enough blood through her new kidney. The kidney needs steady blood flow so that it can produce urine and filter waste. Without it, Pisano’s kidney was failing. She died in July.

Two individuals previously received heart transplants from genetically engineered pigs, the first in January 2022 and a second in September 2023, both at the University of Maryland. Those patients died less than two months after their surgeries and were too sick to leave the hospital.

The latest pig organ recipient, Looney, donated a kidney to her mother in 1999 but developed kidney failure several years later after a pregnancy complication caused damaging high blood pressure. Kidney failure in living donors is extremely rare, with less than 1 percent of people developing it. Those who do end up needing a transplant are given higher priority on the waiting list.

By December 2016, Looney needed dialysis treatment, in which a patient’s blood vessels are hooked up to a machine that does the job of the kidneys—removing excess fluid and waste from the bloodstream. She was placed on the national waiting list for a kidney transplant in early 2017 but couldn’t find a suitable match. Because of exposure to other people’s tissue, through pregnancies and blood transfusions, she became sensitized to nearly every tissue type in the population. High levels of harmful antibodies in her blood meant rejection was likely. She remained on the transplant waiting list for nearly eight years while her blood vessels became weak and damaged from the dialysis.

Slayman, the first pig kidney recipient, was eligible for a human kidney but would have likely waited six to seven years to get one because of his rare blood type. Pisano and the two pig heart patients didn’t qualify for a human organ because of other medical issues.

Looney was running out of options. Her health was declining, and there was little chance of finding a matched human kidney after years of searching. Her doctor, Jayme Locke, then an abdominal transplant surgeon at the University of Alabama at Birmingham, had previously led short-term pig kidney transplants in brain-dead recipients and suggested the experimental procedure as a last resort. Looney’s transplant was approved through the US Food and Drug Administration’s compassionate use program, when an unapproved medical treatment is the only option for a patient with a serious or life-threatening condition.

Locke partnered with Robert Montgomery, director of the NYU Langone Transplant Institute, to carry out Looney’s seven-hour surgery. Locke is now director of the Division of Transplantation at the US Health Resources and Services Administration, part of the Department of Health and Human Services.

Locke said Tuesday that Looney will be spending the next three months in New York City so that she can be monitored closely before returning to her home in Alabama.

Looney received a kidney from a pig with 10 genetic edits developed by Revivicor, a subsidiary of United Therapeutics. Three pig genes known to spark an immune response, as well as a porcine growth hormone receptor, were removed. Six human genes were added to reduce the likelihood of rejection.

Because of the genetic differences between pigs and people, researchers have turned to gene editing to make pig organs more compatible with the human body. But there’s debate in the xenotransplantation field over how many genetic edits are necessary for a pig organ to work long term in a person. For Pisano’s procedure earlier this year, the NYU team used a donor pig with a single genetic edit—a gene knockout to eliminate alpha-gal sugar on the surface of the pigs’ cells. This sugar triggers rapid rejection of pig organs in humans. That donor pig also came from Revivicor.

The Massachusetts team took a different approach with Slayman’s surgery, opting for a pig with 69 genetic edits from biotech company eGenesis. “These distinctions highlight the ongoing evolution of xenotransplantation strategies and underscore the potential benefits of increasing compatibility through more extensive genetic modifications,” says Leonardo Riella, medical director for kidney transplantation at Mass General.

Pig organ recipients still need to take immunosuppressant drugs so that the new organs are not rejected by their immune systems.

While researchers hope pigs will one day provide a source of readily available organs for people who need them, they will first have to demonstrate that they are safe and can function in the human body for longer than a few months. With this latest transplant, scientists are a step closer to carrying out formal clinical trials involving more patients in hopes of answering those questions.

Montgomery is optimistic that Looney will fare better than Pisano because she is in “much better shape physically” and was not at high risk of dying from her kidney disease when she underwent the procedure.

“Our challenge is to learn how to support these kidneys for longer periods of time so that they become a reasonable alternative for this scarce, highly rationed supply of human organs,” Montgomery said.

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