US doctors says the genetically modified pig kidney transplant offers hope for reducing dialysis dependence amid a severe shortage of human donor organs.
A genetically modified pig kidney has functioned inside a human patient for a record 271 days, US doctors have reported, in a development they say could help address the global shortage of donor organs.
The kidney was transplanted into 66-year-old Tim Andrews, who had end-stage kidney disease linked to type 2 diabetes and was facing years of dialysis while waiting for a human donor organ.
Doctors at Massachusetts General Hospital said the case demonstrates the potential of pig organs as a temporary “bridge” for patients awaiting human transplants.
Andrews received the pig kidney on January 25, 2025, and the organ began functioning immediately, filtering his blood and allowing him to avoid months of dialysis.
“I had a little bit of a shortage of time… it becomes very depressing,” Andrews said, recalling that he had been told it could take about seven years to reach the top of the transplant waiting list.
He described the experimental transplant as a source of optimism.
“Hope is the biggest thing, the chance to be free from the [dialysis] machine and live your life,” he said.
The pig kidney continued functioning for 271 days before doctors removed it in October 2025 after its condition deteriorated.
Andrews subsequently underwent dialysis for 82 days before receiving a human donor kidney in January 2026. Doctors say the new kidney is functioning well.
Dr Leonardo Riella of Mass General Brigham’s Centre for Transplantation Sciences said the shortage of donor organs had created a major healthcare crisis.
“We are working really hard to bring hope and we truly feel that xenotransplantation can be an alternative for patients who don’t have a living donor where we could potentially bypass dialysis and get them to a transplant,” Riella said.
Doctors said there were early signs that Andrews’ immune system was rejecting the pig kidney, but the problem was successfully managed by adjusting his medication.
However, after about six months, blood vessels in the transplanted kidney began to suffer damage. The organ became inflamed before eventually failing.
Doctors said the precise cause of the failure remains unclear because there was no evidence of antibodies attacking the pig kidney.
The findings, published in The Lancet, highlight both the potential and remaining challenges of xenotransplantation — the use of organs from animals in human patients.
Pigs are considered promising donors because their organs are broadly similar in size to human organs and the animals can be bred under controlled conditions.
However, an unmodified pig organ would normally trigger a severe immune response in the human body.
To overcome this, researchers have developed genetically modified Yucatan miniature pigs whose organs have undergone 69 genomic modifications.
The modifications remove or alter pig characteristics that trigger the human immune system, introduce human genes to help the organs evade immune attack and disable viruses embedded in pig DNA to reduce the risk of infection.
The need for such alternatives is driven by a severe shortage of donor organs.
In the United States, about 100,000 people are waiting for kidney transplants, while only around 25,000 kidney transplants are performed annually.
In the United Kingdom, more than 7,000 people are also on the kidney transplant waiting list.
The Mass General Brigham team said Andrews’ case demonstrates that xenotransplantation could potentially provide patients with a functioning kidney while they wait for a human donor, reducing or eliminating the need for prolonged dialysis.
The doctors concluded that the case demonstrates both the promise of kidney xenotransplantation and the significant challenges that remain before the procedure can become a widely available treatment.