A groundbreaking development in organ transplantation has set a new record: a kidney harvested from a genetically modified pig has functioned normally in a human patient for 271 days, the longest successful duration ever recorded for this experimental procedure, according to medical teams at Mass General Brigham in the United States. The case, recently published in the *Lancet* medical journal, offers a glimmer of hope amid a persistent global crisis of organ donor shortages that leaves thousands of patients waiting for life-saving treatment every year.
The recipient of the experimental transplant was 66-year-old Tim Andrews, who was living with end-stage kidney disease caused by type 2 diabetes. Like thousands of patients across the United States and the United Kingdom, Andrews faced a years-long wait for a human donor kidney. He was told it could take up to seven years to reach the top of the transplant waiting list, while the average life expectancy for a patient on long-term dialysis is just five years. “I had a little bit of a shortage of time… it becomes very depressing,” Andrews recalled of his ordeal before the procedure. When offered the option of a pig kidney xenotransplant—an organ sourced from another species—he described the opportunity as “hope” and the “light at the end of the tunnel.”
The transplant was performed on January 25, 2025. From the moment surgeons connected the pig kidney to Andrews’ blood vessels, the organ began working to filter his blood, eliminating the immediate need for regular, time-consuming dialysis appointments that had upended his daily life. The pig kidney continued to function without critical failure for 271 days, a new global benchmark for the field of xenotransplantation. Although early signs of immune rejection were detected, clinicians successfully managed the reaction by adjusting Andrews’ immunosuppressant medication. Eventually, after approximately six months, the pig kidney began to fail as inflammation developed and damage accumulated in its blood vessels. It was removed in October 2025, after which Andrews returned to short-term dialysis for 82 days. In January 2026, he received a donor human kidney, which has continued to function well as of the latest clinical updates.
Notably, clinicians report that the pig kidney’s failure was not triggered by the acute antibody-mediated immune rejection that has doomed early xenotransplant attempts. The exact cause of the organ’s decline remains under investigation, marking a key area for future research.
Pigs have long been identified as the most promising candidate species for human xenotransplantation: their organs are roughly the same size as human organs, and controlled farming of pigs for medical use has been refined over decades of research. However, using unmodified pig organs in humans triggers an immediate, devastating immune response, where the body identifies the foreign tissue and launches an attack that destroys the organ within minutes. To overcome this barrier, researchers developed genetically modified Yucatan miniature pigs, with 69 genomic edits designed to “humanize” their organs:
– These edits remove molecular markers on pig cells that the human immune system recognizes as foreign
– They add human genetic material that acts as biological camouflage, hiding the pig tissue from immune detection
– Additional modifications disable endogenous retroviruses embedded in pig DNA, eliminating the risk of cross-species viral infection
Mass General Brigham’s transplant team emphasizes that their successful 271-day outcome proves that genetically modified pig kidneys can act as a life-saving “bridge” for patients waiting for a human donor organ. For patients like Andrews, this bridge means freedom from the relentless cycle of dialysis while they wait, and a far higher chance of surviving long enough to receive a permanent human transplant.
Dr. Leonardo Riella, from the center for transplantation sciences at Mass General Brigham, framed the ongoing organ shortage as a public health 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,” he said.
g the milestone, the research team’s published analysis acknowledges that the case highlights both the enormous promise of xenotransplantation and the critical challenges that remain to be solved before the procedure can become widely available to patients in need. Across the globe, 100,000 people are currently waiting for a kidney transplant in the U.S. alone, with only around 25,000 transplants performed annually. More than 7,000 patients are on the UK’s kidney waiting list, making the search for alternative organ sources a pressing public health priority.