Transplant bridges: In a first, a pig kidney kept a patient alive until he got a human one

RONI CARYN RABIN

Two years ago, Tim Andrews was so worn out that all he wanted to do was sleep. Diabetes and high blood pressure had destroyed his kidneys, and the frequent dialysis treatments that kept him alive by filtering his blood were gruelling. Though only 66, he had no energy or appetite, was too weak to walk and had experienced two heart attacks.

“I was dying,” Andrews said. A kidney transplant could have saved his life, but the organs are in short supply. Roughly 90,000 people are on the waiting list for a kidney transplant, and on average, 11 people die every day while waiting for one, according to United Network for Organ Sharing. And his rare blood type meant that Andrews’ odds of getting a matching human kidney were especially slim.

So when he heard that doctors at Mass General Brigham were transplanting patients with kidneys from genetically modified pigs, he reached out.“I figured, if I’m going to die, I might as well do something for humanity and be part of this experiment,” he said.

Andrews received a genetically modified pig kidney on Jan. 25, 2025, and lived with it for nine months. This year, he became the first known patient to receive a human donor kidney after a pig kidney transplant, a milestone described in a paper published in The Lancet.

His case provides early proof of an intriguing concept in transplant medicine: that pig kidneys could offer “bridges” to transplants with human organs. The kidneys come from pigs that have undergone numerous genetic edits, including some designed to prevent a severe organ rejection response and others to inactivate viruses in the pig genome.

By using the pig kidneys as a stopgap, doctors hope to keep patients alive while they make their way up the waiting list for a human kidney, and to provide a respite from dialysis. “Dialysis causes so much wear and tear that patients become too sick for a transplant, or die waiting,” said Leonardo V Riella, the paper’s lead author and associate director of the Legorreta Centre for Clinical Transplant Tolerance at Mass General Brigham.

The idea that pig kidneys could be used this way wasn’t a given. When researchers first considered the idea, there was a concern that patients who had received a pig kidney might become more prone to rejecting a human kidney later.

But Andrews’ experience, along with that of one other patient, suggests that “it doesn’t seem to change how you react to human tissue at all,” said Mike Curtis, president and CEO at eGenesis, the biotechnology company that produces the genetically modified pigs used at Mass General Brigham and helped fund the study.

“Right now, we don’t think there’s any downside to having a pig kidney followed by a human kidney, but when we started this, we had no idea that that would be true,” Curtis said.