American survives nine months with genetically modified pig kidney

A genetically modified pig kidney has allowed a 66-year-old American to survive nine months without the need for dialysis and until receiving a human transplant. The 271 days that this individual, Tim Andrews, spent with the xenotransplant represents a record duration for an animal-to-human transplant, according to The Lancet magazine.

The interventions for this 'bridge' transplant were carried out throughout 2025 at Mass General Brigham (USA), as detailed in the scientific journal.

The patient suffered 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 chance of dying.

The kidney, which came from a Yucatan miniature pig and was genetically modified - with almost 70 changes - to make it compatible with the immune system, showed signs of functioning after the transplant. Thus, in the first hours it began to produce urine adequately. Two weeks later, however, an episode of rejection occurred, which could be controlled with treatment.

After about six months, however, lesions occurred in the blood vessels of the kidney that progressively advanced. At 271 days, the damage was already irreversible, so it was necessary to remove the transplanted pig organ.

After several months in 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 the scientists emphasize in the publication detailing the results of their work, this milestone highlights both the potential and the aspects that must be improved 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 kidney disease who have developed kidney failure is transplantation, but we simply do not have enough human organs to perform transplants in time," said Leonardo Riella of Mass General Brigham in a statement.

The researcher stressed that the team's vision is that xenotransplantation could help fill this gap: initially as a bridge to stop patients needing dialysis while they wait for a kidney from a human donor and, potentially, as "we demonstrate its long-term safety and durability, as a definitive therapy in its own right."