A 67-year-old man from New Hampshire has become the first person in the world to survive both a genetically modified pig kidney transplant and a subsequent human kidney transplant, according to medical teams at Massachusetts General Hospital. The milestone marks the longest recorded dialysis-free survival following a pig kidney transplant in a living patient, with the pig organ functioning for 271 days before being replaced by a human donor kidney in February 2025.
The breakthrough occurred as part of an experimental procedure known as xenotransplantation, which involves transplanting organs from animals into humans. The pig kidney was genetically modified to reduce the risk of rejection and improve compatibility with the human immune system. The patient, Tim Andrews, had been suffering from end-stage kidney failure due to type 2 diabetes and had spent two years on dialysis before the procedure.
Immediate medical outcomes
Andrews initially received the pig kidney in January 2025, which allowed him to avoid dialysis for over nine months. The organ functioned successfully during this period, providing Andrews with a temporary solution while he awaited a human donor. However, the pig kidney eventually failed, requiring a brief return to dialysis before a human kidney became available. Andrews received the human transplant in February 2025 and is reported to be recovering.
Medical teams at Massachusetts General Hospital described the procedure as a proof of concept for xenotransplantation, demonstrating that animal organs can serve as a "bridge" to human transplants. The hospital’s findings were published in the Lancet journal, highlighting the potential of genetically modified pig organs to address the global shortage of human organs for transplantation.
Patient background and motivation
Andrews, a retired pensioner, had been on dialysis three days a week for two years prior to the pig kidney transplant. His condition had deteriorated significantly, leaving him fatigued and unable to walk due to muscle wasting. After suffering a heart attack in mid-2024, Andrews told doctors he felt he was "going to die" and sought alternative treatments. His case followed the high-profile pig kidney transplant of Richard Slayman, a 62-year-old Massachusetts man who received a genetically modified pig kidney in 2024 but died two months later from an unrelated heart condition.
Andrews’ motivation for pursuing the experimental procedure was driven by the dire prognosis of waiting for a human donor. He was informed that the average wait time for a kidney transplant in the U.S. could exceed seven years, while the average survival time on dialysis is only about five years. The pig kidney transplant offered him a temporary reprieve and renewed hope.
Global context and organ shortage
The success of Andrews’ pig kidney transplant highlights the urgent need for alternative solutions to the global organ shortage. In the U.S., approximately 100,000 people are currently on the kidney transplant waiting list, but only 25,000 transplants are performed annually. In the U.K., more than 7,000 people are awaiting kidney transplants. Xenotransplantation is being explored as a potential solution to bridge the gap until human donor organs become available.
Genetically modified pig organs are considered a promising option due to their anatomical and physiological similarities to human organs. Pigs are bred specifically for this purpose, with their organs modified to reduce the risk of rejection and transmission of diseases. The U.S. Food and Drug Administration (FDA) has approved certain xenotransplantation trials, but the procedure remains experimental and carries significant risks.
Ethical and scientific considerations
While the procedure offers hope for thousands of patients, it also raises ethical and scientific questions. Critics argue that xenotransplantation could pose risks such as zoonotic disease transmission (the transfer of animal pathogens to humans) or long-term complications from immune suppression. Proponents counter that the potential benefits—such as saving lives and reducing reliance on dialysis—outweigh the risks, particularly given the severe organ shortage.
Medical experts emphasize that Andrews’ case is a significant step forward but caution that further research is needed before xenotransplantation can become a standard treatment. The long-term viability of pig organs in humans, the risk of immune rejection, and the ethical implications of using animal organs for human transplantation remain active areas of study.
Future implications
The success of Andrews’ procedure has sparked discussions about the future of xenotransplantation and its potential to revolutionize organ transplantation. If further trials prove successful, genetically modified pig organs could become a viable option for patients awaiting human transplants, particularly in cases where human donor organs are scarce or unavailable.
For now, Andrews’ case serves as a landmark in medical history, offering a glimmer of hope to patients worldwide who are desperate for life-saving organ transplants. His story underscores the urgent need for continued innovation in medical science and the importance of addressing the global organ shortage.