A man in the United States lived for a record nine months with a transplanted, genetically modified pig kidney before receiving a human donor organ, according to a study published in the medical journal The Lancet.
The patient, Tim Andrews of New Hampshire, had end-stage kidney failure caused by type 2 diabetes. Because of his rare blood type, doctors estimated he had only a 9 percent chance of receiving a human kidney within five years, while his risk of dying or being removed from the transplant waiting list exceeded 40 percent.
A pig kidney with 69 gene edits
In January 2025, surgeons transplanted a kidney from a genetically modified pig named Wilma into Andrews. Wilma's genome had undergone 69 edits designed to stop his immune system from rejecting the organ.
Xenotransplantation, the transplant of organs between species, has been explored for years as a way to ease shortages of human donor organs, with pigs favored because their organs are similar in size to human ones. Genetic editing is used to remove pig genes that trigger immune rejection and to add human genes that help the organ function normally in a person.
Nine months without dialysis
Wilma's kidney functioned for nine months, during which Andrews needed no dialysis. He was able to cook, walk his dog and even vacuum his home, activities he had been unable to manage for years because of his illness.
The pig kidney eventually began to fail, but by that point a human donor had been found, and doctors replaced the pig organ with the donor kidney.
A world first
Doctors said it was the first time a pig kidney had been used worldwide as a temporary "bridge" to keep a patient alive until a human donor organ became available. Previous records for transplanted pig kidneys had not exceeded two months.
Andrews described the operation as a miracle.
