A genetically modified pig kidney has kept a 66-year-old New Hampshire man with end-stage kidney disease alive for a record nine months, serving as a temporary bridge to a human organ transplant, according to the Lancet medical journal. Tim Andrews received the organ from a Yucatan miniature pig named Wilma after undergoing surgery at Massachusetts General Hospital on January 25, 2025, marking the first time a porcine xenograft has successfully functioned as a bridge to a human transplant in a living person.
Patient Health Background and Organ Shortage Crisis
End-stage kidney disease caused by type 2 diabetes left Andrews with a nine percent chance of receiving a human kidney within five years, against a more than 40 percent risk of dying or dropping off the waiting list, according to clinical records published in the Lancet. Kidney transplantation provides the best survival and quality of life for patients with renal failure, but global demand far outstrips the supply of human organs.
“The organ shortage is the greatest crisis we have right now in transplantation,” said Dr. Leonardo Riella of the Center for Transplantation Sciences and the Division of Nephrology at Mass General Brigham. “We know that the best treatment option for patients with end-stage kidney disease who have developed renal failure is transplantation, but we simply don’t have enough human organs to transplant in a timely manner.”
Genetic Engineering and Surgical Procedure Details
Before the January procedure, Wilma the pig received 69 edits to her genome. These modifications dodged viruses that pose risks to humans and enhanced organ compatibility to lower the risk of immune rejection, according to the research team at Mass General Brigham. Andrews lived with the edited kidney for 271 days—the longest dialysis-free survival following a pig kidney xenotransplantation in a living human—before the organ failed and doctors removed it.
Did you know? Previous pig kidney transplants into living humans lasted significantly shorter periods. A 2024 procedure ended after 52 days due to unrelated heart problems, and no prior studies documented xenograft survival beyond two months, according to the Lancet.
Post-Transplant Recovery and Human Donor Transition
During the nine months the pig kidney functioned, Andrews remained free of dialysis and reported a dramatic return to normal activities. “I was alive, and I hadn’t been in a long time,” Andrews said, noting he could cook, vacuum, and take long walks with his dog, Cupcake. After roughly six months, damage developed in the pig kidney’s blood vessels, progressing to organ failure by the ninth month.
Following several months back on dialysis, Andrews received a kidney from a dead human donor, which functioned well during six months of follow-up, according to the Lancet. Medical evaluations detected no new antibodies against human tissue, indicating the pig kidney did not complicate the subsequent human transplant, and tests found no pig viruses or pathogens.
Frequently Asked Questions
How long did the pig kidney last in Tim Andrews?
The genetically modified pig kidney functioned for nine months, or 271 days, keeping Andrews free of dialysis before it began failing and surgeons removed it.
What modifications were made to the pig’s genome?
Wilma the Yucatan miniature pig received 69 edits designed to avoid viruses dangerous to humans and to increase immune compatibility, reducing the likelihood of organ rejection.
What happened after the pig kidney failed?
Andrews spent several months back on dialysis before receiving a kidney from a deceased human donor, which worked successfully during subsequent follow-ups.
Are pig kidney transplants available to the general public?
Not yet. Researchers at Mass General Brigham caution that this involved a single patient with no comparison group, and further clinical trials are necessary to establish long-term safety and durability.
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