A genetically modified pig kidney allowed a 66-year-old American to survive nine months without needing dialysis until receiving a human transplant. The 271 days that this individual, Tim Andrews, spent with the xenotransplant represent a record duration for an animal-to-human transplant, as reported by the journal The Lancet.
The interventions for this 'bridge' transplant were carried out throughout 2025 at Mass General Brigham (USA), as detailed in the scientific journal.
The patient was suffering from kidney failure caused by type 2 diabetes. Before undergoing the xenotransplant, his doctors estimated that he had a 9% chance of receiving a human kidney within five years, despite his high chances of dying.
The kidney, which came from a miniature Yucatan pig and was genetically modified - with nearly 70 changes - to be compatible with the immune system, showed signs of functioning after the transplant. Thus, it began producing urine properly within the first few hours. However, two weeks later, a rejection episode occurred, which was able to be controlled with treatment.
After about six months, however, lesions in the kidney's blood vessels developed progressively. At 271 days, the damage was irreversible, leading to the need to remove the transplanted pig organ.
After several months during which he had to undergo dialysis again, he was able to receive a kidney from a deceased human donor, which functioned well during the six months of follow-up.
As emphasized by the scientists in the publication detailing the results of their work, this milestone highlights both the potential and the aspects that need improvement in xenotransplants as a bridge solution for patients on the waiting list for human kidneys.
"We know that the best therapeutic option for patients with end-stage renal disease who have developed kidney failure is transplantation, but we simply do not have enough human organs to perform transplants in time," stated Leonardo Riella, from Mass General Brigham in a press release.
The researcher highlighted that the team's vision is that xenotransplantation could help address this shortage: initially as a bridge for patients to stop needing dialysis while waiting for a human donor kidney and potentially, as we "demonstrate its safety and long-term durability, as a definitive therapy in its own right."
"Scientific and biotechnological advances in the last five years have raised the possibility that xenotransplants could become a clinical reality in the medium to long term," stated a few months ago to this newspaper Pablo Ramírez, head of the General Surgery and Digestive System Service at the Virgen de la Arrixaca Hospital, scientific director of the Pascual Parrilla Murcian Institute of Biosanitary Research in Murcia, and one of the Spanish researchers with the most experience in xenotransplants. His team has requested authorization from the National Transplant Organization (ONT) to carry out a clinical trial of genetically modified pig liver xenotransplantation in patients dying from fulminant hepatitis and without a human donor.