A 66-year-old man suffering from end-stage kidney disease has successfully lived for a record-breaking nine months with a genetically modified pig kidney. The procedure, which served as a bridge to a subsequent human transplant, represents a significant milestone in the field of xenotransplantation. Tim Andrews, a resident of New Hampshire, had been battling kidney failure stemming from type 2 diabetes and faced a dire prognosis, with only a 9% chance of receiving a human kidney within five years.
Surgeons at Mass General Brigham in Massachusetts performed the pioneering transplant using an organ from a Yucatan miniature pig named Wilma. Before the surgery in January 2025, Wilma’s genome underwent 69 specific edits. These modifications were intended to reduce the risk of immune rejection and prevent the transmission of viruses that could potentially affect humans.
For 271 days, the pig kidney functioned effectively, allowing Andrews to remain free from dialysis. During this period, he reported a significant improvement in his quality of life, noting that he was able to perform daily tasks like cooking and vacuuming, as well as taking walks with his dog, Cupcake. Andrews described the experience as a “miracle” that restored his sense of being alive.
Dr. Leonardo Riella of the Center for Transplantation Sciences at Mass General Brigham highlighted the global organ shortage as a primary crisis in modern medicine. He noted that while human transplantation remains the gold standard for treating renal failure, the lack of available organs necessitates new approaches. The team envisions xenotransplantation as a viable solution, initially serving as a temporary bridge for patients on waiting lists and potentially as a destination therapy once long-term safety and durability are established.
The pig kidney eventually began to fail after roughly six months due to damage in its blood vessels, and it was removed after nine months of use. Following a brief return to dialysis, Andrews successfully received a kidney from a deceased human donor. Follow-up examinations conducted six months later showed that the human organ was functioning well. Medical teams observed no new antibodies against human tissue and detected no pig viruses or pathogens, suggesting the initial xenograft did not impede the success of the subsequent human transplant.
While this case marks the longest period of dialysis-free survival following a pig kidney xenotransplantation in a living human, researchers caution that the results are based on a single patient. They emphasized that the success relied on intensive specialist care and careful patient selection, and that further clinical trials are essential to validate the procedure for broader medical application.
Transplanting genetically engineered pig organs has long been proposed as a solution to the organ shortage. But the first pig kidney transplant into a living person, in 2024, ended after 52 days when the patient died from unrelated heart problems, and no previous studies had documented xenograft survival beyond two months, according to the Lancet.
“The patients are the true pioneers here,” Riella said. “By stepping forward and being willing to participate in these early stage studies, they are advancing the science. Without their trust and courage, we would not be able to do what we do.”
