A woman has lived for 285 days with a genetically modified pig kidney without needing dialysis, setting a new record and offering fresh evidence that animal organs could one day help patients waiting for human transplants.
The woman received the kidney at Massachusetts General Hospital on Nov. 22, 2025. The organ was still functioning Thursday, according to eGenesis, the Cambridge, Massachusetts-based biotechnology company that developed it.
The milestone surpasses the previous record of 271 days, set by Tim Andrews. It marks another advance in pig kidney transplantation, a field that reached a major milestone in 2024 when doctors transplanted a genetically modified pig kidney into a living person for the first time.
The woman is the fifth person to receive an eGenesis kidney through the U.S. Food and Drug Administration’s expanded access pathway. The program allows some patients with serious or life-threatening conditions to receive experimental treatments when satisfactory alternatives are unavailable.
Gene editing aims to overcome rejection
Pig organs are similar in size and function to human organs, making them possible candidates for xenotransplantation, the transfer of organs between species. Scientists are also exploring other approaches, including efforts to grow human kidneys inside pig embryos.
A historic breakthrough in transplant medicine has demonstrated that a genetically modified pig kidney can sustain human life without dialysis for nine full months. Detailed in The Lancet, 66-year-old Tim Andrews lived dialysis-free for 271 days with an organ engineered using… pic.twitter.com/i5vS1pgnde
— Science & Nature (@ScienceIsNew) September 4, 2026
The human immune system, however, can attack pig tissue as foreign. EGenesis uses CRISPR gene editing to reduce that risk. Researchers removed pig genes that could trigger an immune response and added human genes intended to improve compatibility.
The research could help address a major shortage. More than 95,000 people are waiting for kidneys in the United States, while fewer than 28,000 kidney transplants were performed in 2025. Organ availability remains a challenge worldwide, even as countries including Greece report increases in organ donations and transplants.
Earlier transplants offer important clues
Andrews received a pig kidney in January 2025. Doctors removed it in October after its function declined. He returned to dialysis before receiving a human kidney in January 2026.
Earlier experiments have also shown the uncertainties surrounding xenotransplantation. Richard “Rick” Slayman, who underwent the first pig kidney transplant in a living human, died nearly two months later, although his transplant team said there was no indication his death resulted from the procedure.
A study published Thursday in The Lancet examined Andrews’ case. Researchers attributed the loss of kidney function to thrombotic microangiopathy, which involves damage to small blood vessels and tiny blood clots.
EGenesis is using findings from the transplants to adjust the immunosuppressive treatment given to recipients.
Clinical trial planned for 2027
The FDA has cleared eGenesis to conduct a clinical trial involving up to 33 kidney failure patients ages 50 to 70 who are waiting for human organs. The trial is expected to begin in 2027. Until then, the company plans additional transplants through expanded access.
Pig kidneys remain experimental, and larger studies are needed to establish their long-term safety and effectiveness. After reaching 285 days, eGenesis has set its next target: keeping a transplanted pig kidney functioning for a full year.
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