A genetically modified pig kidney functioned in a 66-year-old US man for 271 days, setting a record for the longest period a pig kidney has remained functional in a human recipient.
Tim Andrews received the experimental transplant at Massachusetts General Hospital in January 2025 after developing end-stage kidney disease linked to type 2 diabetes. The procedure allowed him to stop dialysis while he waited for a human donor kidney.
“I had a little bit of a shortage of time, it becomes very depressing,” Andrews said, describing his condition before the transplant.
He said the possibility of receiving a pig kidney gave him renewed hope, particularly the prospect of living without dialysis.
The genetically modified kidney began functioning immediately after surgery and continued to work for nearly nine months. Doctors removed it in October 2025 after its blood vessels began to deteriorate, causing inflammation and eventual organ failure.
Doctors said the kidney initially showed signs of rejection, but the reaction was controlled by adjusting Andrews’ medication. However, after about six months, damage to the organ’s blood vessels developed. There was no evidence that antibodies had attacked the kidney, leaving the exact cause of its failure unclear.
After the pig kidney was removed, Andrews underwent dialysis for 82 days before receiving a human donor kidney in January 2026. Doctors say the human kidney is functioning well.
The donor pig had undergone multiple genetic modifications intended to improve compatibility with the human immune system and reduce the risk of infections associated with pig DNA.
Dr Leonardo Riella of the Mass General Brigham Centre for Transplantation Sciences said xenotransplantation could help address the shortage of human donor organs.
“We truly feel that xenotransplantation can be an alternative for patients who don’t have a living donor,” Riella said.
The case highlights both the potential and limitations of xenotransplantation, with researchers hoping genetically modified pig organs could eventually serve as temporary “bridges” for patients awaiting human transplants and help reduce their dependence on dialysis.
