A pig kidney transplanted into a 66‑year‑old man has worked inside his body for 271 days – the longest period ever recorded for a xenotransplant – offering fresh hope to thousands awaiting donor organs. Tim Andrews, who suffers from end‑stage kidney disease caused by type 2 diabetes, received the genetically modified organ on 25 January 2025 at Massachusetts General Hospital. The kidney began filtering blood immediately and continued to do so until its removal in October that year, after which he underwent 82 days of dialysis before receiving a human donor kidney in January 2026.
The Transplant Journey
Andrews described the experience as a lifeline. “I had a little bit of a shortage of time… it becomes very depressing,” he said, reflecting on the years he faced while waiting for a human kidney. He was told the average wait could stretch to seven years, yet most patients survive only about five years on dialysis. The pig transplant, he added, gave him “hope” and the “light at the end of the tunnel”. “Hope is the biggest thing, the chance to be free from the [dialysis] machine and live your life,” he told clinicians. After the pig organ was removed, a short course of dialysis bridged the gap until a compatible human kidney became available, which has since been functioning well.
Science Behind the Pig Organ
The kidney came from a Yucatan miniature pig that underwent 69 genomic alterations designed to make its tissues less visible to the human immune system. Scientists removed pig‑specific markers that trigger attack, added human DNA sequences that act like camouflage, and disabled endogenous viruses that could cause infection. Despite these safeguards, early signs of immune rejection appeared and were managed by adjusting Andrews’ medication. Around the six‑month mark, however, blood vessels within the kidney began to deteriorate, leading to inflammation and gradual loss of function. The Lancet paper on the case notes: “This case illustrates both the promise and the remaining challenges of clinical kidney xenotransplantation.”
Challenges and Next Steps
Dr Leonardo Riella of the centre for transplantation sciences at Mass General Brigham stressed the gravity of the organ shortage. “We are in a crisis,” he said, adding that the team is “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.” In the United States, roughly 100,000 people await a kidney while only about 25,000 transplants occur each year; more than 7,000 are on the waiting list in the UK. Although the pig kidney ultimately failed, the 271‑day run demonstrates that genetically edited organs can support human physiology for an extended period, providing a valuable bridge to definitive transplantation.
Why it Matters
This milestone shows that xenotransplantation is moving beyond experimental theory into a tangible, albeit imperfect, solution for a dire public‑health problem. By extending the time a patient can live without dialysis, pig organs could reduce the immediate mortality risk associated with end‑stage kidney failure and alleviate pressure on overstretched transplant programmes. Continued refinement of genetic modifications and immunosuppressive strategies may one day allow such grafts to function indefinitely, transforming the lives of tens of thousands who currently face years of uncertain waiting and grueling treatment.
