A Pig Kidney Breaks Records—Could It Be the Future of Transplants?

A 54-year-old American man has become the latest recipient of an experimental pig kidney transplant, marking another significant step in the development of xenotransplantation as a potential solution to the critical shortage of human organs. Bill Stewart, an athletic trainer from Dover, New Hampshire, underwent the procedure at Massachusetts General Hospital on June 14 and has since returned home. He is off dialysis and gradually resuming work, expressing optimism about the future of the technology and its potential to inspire hope among others facing similar challenges [1].

Stewart’s case is particularly noteworthy as he is not in a terminal condition, unlike many previous xenotransplant recipients. This shift reflects a broader strategy among researchers to test the long-term viability of gene-edited pig organs in healthier patients. Prior to the transplant, Stewart had been undergoing dialysis for more than two years after his kidneys failed due to high blood pressure. With his blood type O, his chances of receiving a matching human kidney were estimated at up to seven years, prompting him to volunteer for the experimental procedure [1].

The Massachusetts General Hospital team has also reported progress with Tim Andrews, a 67-year-old New Hampshire resident whose pig kidney has kept him off dialysis for over seven months—setting a new record for the longest survival of a xenotransplanted organ in the United States. Before this, the longest known duration for such a transplant was 130 days. These results have led to the Food and Drug Administration approving a larger clinical trial led by biotech firm eGenesis, which plans to study gene-edited pig kidney transplants in 30 patients aged 50 or older who are on dialysis and the transplant list [1].

The pig organs used in these procedures are genetically modified to reduce the likelihood of rejection by the human immune system. Scientists employ CRISPR technology to remove a gene responsible for a carbohydrate known as alpha gal, which triggers rapid rejection of pig organs in humans. This genetic engineering is a key innovation enabling these experimental transplants to function at all [2].

While early results are promising, researchers caution that it is still too early to determine how long such organs might function in the long term. Dr. Leonardo Riella, a kidney specialist at Massachusetts General Hospital, noted that even a year of dialysis-free life would represent a significant improvement for patients waiting on transplant lists. The ultimate goal, however, is to develop organs that can serve as permanent solutions [2].

Complementing eGenesis’s efforts, United Therapeutics, another developer of gene-edited pig organs, is preparing to launch its own FDA-approved clinical trials. These trials will expand the dataset on the effectiveness of xenotransplants and help researchers better understand how the organs perform across a broader and more varied patient population. According to Mike Curtis, CEO of eGenesis, the next phase of research will be crucial in determining the general applicability of this technology [2].

Source:

[1] Another New Hampshire man gets a pig kidney as transplant trials expand (https://abcnews.go.com/Health/wireStory/new-hampshire-man-gets-pig-kidney-transplant-trials-125357267)

[2] Pig kidney transplants take a step forward with approval of human trials (https://www.cnn.com/2025/09/08/health/pig-kidney-transplant-human-trial-fda)