Pig kidney functions for record 271 days after transplant into human

A genetically modified pig kidney remained functional for a record 271 days after being transplanted into a 66-year-old man in the United States, offering fresh evidence that animal organs could one day help bridge the gap for patients waiting for human donors.

The transplant was performed on January 25, 2025, at Mass General Brigham on Tim Andrews, whose kidneys had failed completely because of type 2 diabetes. He had been dependent on dialysis for an extended period and was suffering from end-stage kidney disease.

The pig kidney began functioning soon after the operation and continued working for nearly nine months. Doctors later removed the organ after its performance declined. Andrews returned to dialysis for 82 days before receiving a human donor kidney in January this year, which is currently functioning well.

Doctors initially detected signs of an immune response against the transplanted kidney but were able to control them by adjusting the type and dosage of medication. About six months after the transplant, however, the kidney developed signs of blood-vessel damage followed by inflammation, and its function gradually deteriorated.

The precise cause of the decline remains unclear. Notably, doctors found no evidence of a direct antibody attack against the pig kidney.

The case highlights the potential of xenotransplantation, the transplantation of animal organs into humans, as a possible solution to the severe shortage of donor kidneys. Nearly 100,000 people in the United States are reportedly waiting for kidney transplants, while only about 25,000 are performed each year.

Pigs are considered promising donors because their organs are similar in size to human organs. But ordinary pig organs trigger a powerful human immune response and can be rapidly rejected.

To overcome that barrier, researchers used genetically modified Yucatan miniature pigs. The donor kidney used in Andrews’ transplant came from an animal carrying 69 genetic modifications designed to reduce immune rejection, add selected human genes and lower the risk posed by pig-borne viruses.

Leonardo Riella of Mass General Brigham’s Transplantation Sciences Center said xenotransplantation could become an important option for addressing the shortage of donor organs.

The findings, published in the medical journal The Lancet, demonstrate both the potential of pig kidneys for human transplantation and the significant biological challenges that still need to be overcome.