Modified pig kidney allows patient to go nine months without dialysis

A genetically modified pig kidney allowed a 66-year-old man with end-stage renal failure to go off dialysis for a record nine months, when it stopped working, and he underwent a human donor transplant shortly after.

A study published in The Lancet magazine gives details of the case, treated at the Mass General Brigham Hospital (Massachusetts, USA), which represents the first experience in which a pig kidney is used as a temporary 'bridge' until the availability of a donor organ.

The patient, Tim Andrews, suffered from kidney failure caused by type 2 diabetes and was estimated to have a 9% chance of receiving a human kidney within five years, compared to a greater than 40% risk of dying or being removed from the waiting list.

The kidney, which came from a miniature pig from Yucatán and was genetically modified to be compatible with the immune system, was transplanted in January 2025 and it took a year until he could access a human one.

The pig kidney functioned immediately and, although there was an early episode of rejection, which resolved with treatment, no transmission of porcine pathogens was detected.

The patient was able to spend 271 days without the need for dialysis, which represents the longest survival without such treatment after a porcine xenotransplantation.

After about six months, lesions occurred in the blood vessels of the kidney that progressed to organ failure, so it was removed, the magazine indicates.

The patient did not produce any detectable antibodies against pig kidney, suggesting a different mechanism than that typically seen in organ transplant rejection.

After several months of returning to dialysis, he was able to receive a kidney from a deceased human donor, which functioned well during six months of follow-up.

Could more people benefit?

The authors caution that this is a single person with no comparison group and that the result reflects careful patient selection and intensive specialized care that may not be available elsewhere.

The results highlight both the potential and the aspects that need to be improved in xenotransplantations as a bridging solution for patients on the human kidney waiting list, Mass General Brigham said in a statement.

"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.