One of the first recipients in the world of a genetically modified pig kidney has become the first in that small group of pioneers to receive a human kidney, reports CNN.
Tim Andrews (67) was among the first recipients ever of a genetically modified pig kidney. A diabetic, who was living with end-stage kidney disease, he received a pig kidney on 25 January 2025, and lived with it for a record 271 days.
After his body rejected the organ, it was removed in October, and Andrews returned to dialysis – which kept him alive but made him so miserable it had driven him to the experimental xenotransplant in the first place.
But after his transplant surgery, Andrews now expects to be discharged to his home in New Hampshire this week, just days after the milestone organ transplant that made him a living example of the promise of xenotransplantation: organs from animals may help keep humans alive and healthy enough for a longer-term solution and a new shot at life.
An answer to organ shortages
Xenotransplantation has been touted as a possible solution to the current shortage of organ donors. At any given time in the US, there are more than 100 000 people waiting for an organ, about 80% of them in need of kidneys. But only the sickest of the sick are listed; just one in eight patients with end-stage renal disease are on the waitlist.
Of the more than 800 000 people with kidney failure, nearly 70% are on dialysis. But dialysis is trying to compress into just a few hours every week the work that the body typically does 24/7. The five-year survival rate for patients on dialysis hovers around 40%.
“Dialysis is not able to reproduce what the body needs in terms of clearing the waste,” said Dr Leonardo Riella, medical director of kidney transplantation at Mass General Brigham hospital and Andrews’ doctor. “It has a huge burden on the patient, both in their quality of life but most importantly on their health.”
Andrews was hooked up to a dialysis machine three days a week for up to six hours at a time. Six months after starting dialysis the first time, he had a heart attack.
While organs remain in short supply, Riella sees xenotransplantation as a solution.
“Even if it is a bridge,” Riella said, “it would be better than (Andrews) just staying on dialysis.”
‘This will do something for humanity’
For Andrews, getting the xenotransplant wasn’t just a matter of hope away from dialysis but hope for patients with end stage renal disease.
“This will do something for humanity,” he told CNN chief medical correspondent Dr Sanjay Gupta.
But the path forward had ups and downs. He took 52 pills a day to help keep his pig kidney, which he named Wilma, and immune system in agreement. Ultimately, over the course of nine months, the kidney began showing signs of rejection. He had two infections. Riella said they adjusted Andrews’ immunosuppressant protocol, but the kidneys had become damaged in the process.
“There was some damage to the filters of the kidney that unfortunately, were not reversible,” Riella said. Ultimately, they removed Wilma, and Andrews had to return to dialysis.
Mike Curtis, President and CEO of eGenesis, the company that provided the donor pig for Andrews’ kidney, said it was a slow rejection that scientists could see coming for months.
“We just could not figure out how to how to push it back,” Curtis said.
But biopsies and research into Andrews and the pig kidney may have helped them pinpoint what led to the rejection, which may help future kidney recipients.
“We have a much better idea of what was causing that low level rejection, so we can then tune the suppression,” Curtis said.
Andrews’ experience has helped refine treatment for the next xenotransplant patients. Since his surgery in January 2025, Mass General and eGenesis have teamed up to perform two more xenotransplants before starting a clinical trial in the near future.
An alternative to dialysis
But Riella also sees the xenotransplant as a success for Andrews. Wilma was able to keep him off dialysis for nine months. After Andrews returned to dialysis, his overall function dropped again, and he was losing muscle mass and energy.
At this point, Riella said, the comparison of xenotransplant may not be to a human kidney but to dialysis. “It’s a much better treatment to maintain the kidney function compared with what dialysis is able to offer,” he said. “Our goal is to basically ban dialysis as a long-term treatment.”
But an alternative to dialysis isn’t the end goal, said Dr Robert Montgomery, director of the NYU Langone Transplant Institute.
Montgomery wasn’t involved in Andrews’ care but has also been at the front of the xenotransplant field.
“As this gets better and xenografts last longer, it will be a destination,” said Montgomery, who was the first doctor to transplant pig organs into brain- dead patients and is leading the first FDA-cleared clinical trial into xenotransplant at NYU.
Montgomery believes that xenotransplant will be a viable solution for patients within the next five years. “In the future I think a single patient with renal failure will cycle through both xenografts and allografts throughout their lifetimes.”
Andrews said he has no doubt that Wilma was key to getting him to this point.
“If I didn’t take Wilma, I’d have been dead by now. I wasn’t going to make it another year,” Andrews said. “I’m looking at years now. I can think ahead.”
He thanked the family of his donor, who has not been identified.
“I grieve with you. It’s got to tear you apart, but … the donation has saved my life, and given hope to millions. Your family member is a hero… not just to me, but to the world,” Andrews said.
“I’ll never be able to repay you, but I promise you it’ll be in my heart. And it will be cared and loved for as long as I live.”
See more from MedicalBrief archives:
Pig kidney removed from patient after record nine months
US pig kidney man ‘doing well’ as transplant trials due to start
Transplant doctors remove pig kidney from patient after four months
Pig kidney removed from transplant patient after complications