‘Amazing feat’: US man still alive six months after pig kidney transplant Overview A 67-year-old US man, Tim Andrews, remains alive more than six months after receiving a kidney from a genetically modified pig. This marks the longest survival of a pig organ in a living human. The transplant represents a significant milestone in xenotransplantation (transplanting animal organs into humans). Patient Background Tim Andrews had end-stage kidney disease and had been on dialysis for over two years before surgery in January. Since the transplant, he has been free from dialysis. He was among three patients who received genetically modified pig kidneys from eGenesis on compassionate grounds. Significance of Six-Month Survival The first six months post-transplant are the riskiest for recipients due to risks like anemia and graft rejection. Wayne Hawthorne, transplant surgeon at the University of Sydney, notes that surviving six months indicates excellent outcomes. A 12-month survival would be an even more remarkable milestone. Previous Cases Previous longest survival: Towana Looney, a 53-year-old US woman, survived 4 months and 9 days with a pig kidney before organ rejection necessitated removal. Another patient, Bill Stewart (54 years old), will have reached three months survival by mid-September. Genetic Modifications of the Pig Kidney The pig kidney had three genetic modifications: Removal of three antigens to prevent rejection. Addition of seven human genes to reduce inflammation and bleeding risks. Deactivation of endogenous pig retroviruses. Xenotransplantation Progress Between the 1960s and 1990s, survival times for animal organ transplants ranged from minutes to 70 days. More recent pig organ transplants typically resulted in survival of a couple of months. The recent successes demonstrate significant progress in the field. Regulatory and Clinical Trials The U.S. FDA approved the first clinical trial for genetically modified pig kidneys earlier this year, led by United Therapeutics. eGenesis has received FDA approval to trial its modified pig kidney in up to 33 patients aged 50+ with end-stage kidney disease. eGenesis and OrganOx (UK) have approval to test genetically modified pig livers' transplant safety as of April 2025. Related Information Pig-organ transplants are advancing with multiple human recipients teaching scientists valuable lessons. Clinical trials are bringing pig-to-human organ transplants closer to routine application. Genetically modified pig organs are also being tested in liver transplants. Article Details Author: Rachel Fieldhouse Published: 08 September 2025 in Nature (Volume 645, pages 571-572) DOI: 10.1038/d41586-025-02851-w --- Image Caption Tim Andrews leaving Massachusetts General Hospital in January 2025 after receiving a genetically modified pig kidney. Credit: Kate Flock/Massachusetts General Hospital --- Related Articles (from Nature) Pig-organ transplants: what three human recipients have taught scientists First pig kidney transplant in a person: what it means for the future First pig liver transplanted into a person lasts for 10 days Monkey survives for two years after gene-edited pig-kidney transplant Clinical trials for pig-to-human organ transplants inch closer --- Summary Tim Andrews’ survival six months post genetically modified pig kidney transplant is a historic achievement signaling major progress in xenotransplantation. Genetic alterations to prevent rejection and complications have improved outcomes drastically compared to past decades. Ongoing and