Edited Pig Kidney Buys Patient Nine Months Before Human Transplant

A genetically modified pig kidney kept a seriously ill man alive without dialysis for nine months before doctors replaced it with a human kidney, according to reporting by The Guardian and details published in the Lancet. Tim Andrews, 66, had end-stage kidney disease linked to type 2 diabetes. Doctors estimated that he had only a 9% chance of receiving a human kidney within five years, while his risk of dying or being removed from the waiting list was more than 40%. Surgeons at Massachusetts General Hospital transplanted the kidney in January 2025. The donor was Wilma, a Yucatan miniature pig whose genome had undergone 69 edits. The modifications were intended to reduce the likelihood of immune rejection and limit the risk from viruses that could affect humans. The transplanted organ functioned for 271 days, allowing Andrews to remain free of dialysis. During that period, he said he was able to cook, vacuum and take long walks with his dog. The transplant was also the first reported use of a pig kidney as a temporary bridge to a human kidney. After about six months, damage appeared in the pig kidney’s blood vessels and progressed to organ failure. Doctors removed it roughly nine months after the transplant, and Andrews returned to dialysis for several months. He then received a kidney from a deceased human donor, which was functioning well after six months of follow-up. The medical team reported that Andrews developed no new antibodies against human tissue, suggesting the pig transplant did not prevent the later human transplant from working. They also detected no pig viruses or other pig pathogens. Earlier attempts at pig-kidney transplantation have not lasted as long. The first transplant of a pig kidney into a living person, performed in 2024, ended after 52 days when the recipient died from unrelated heart problems. The Lancet reported that previous studies had not documented survival beyond two months. Researchers at Mass General Brigham cautioned that Andrews was a single, carefully selected patient who received intensive specialist care, with no comparison group. They said further clinical trials are necessary before the approach can be assessed more broadly, while describing xenotransplantation as a possible way to help patients waiting for scarce human organs.