• Posted September 9, 2025

New Hampshire Man Doing Well After Experimental Pig Kidney Transplant

A 54-year-old New Hampshire man is recovering well after receiving an experimental pig kidney transplant.

Bill Stewart, an athletic trainer from Dover, underwent the procedure June 14 at Massachusetts General Hospital (Mass General) in Boston. “I really wanted to contribute to the science of it,” Stewart told The Associated Press.

Stewart’s case marks another step forward for the Mass General team, which is also following the progress of Tim Andrews, a New Hampshire man who has now lived seven months with a transplanted pig kidney — the longest known survival time for a gene-edited pig organ to date. 

The previous record was 130 days.

Based on lessons from these early cases, the U.S. Food and Drug Administration (FDA) has granted approval to biotech company eGenesis to launch a clinical trial that will transplant gene-edited pig kidneys into 30 patients who are 50 or older and on dialysis while awaiting a human kidney, The Associated Press said.

“Right now we have a bottleneck,” said Dr. Leonardo Riella, a kidney specialist at Mass General who will help spearhead the upcoming trial.

More than 100,000 people are on the U.S. transplant waiting list, most of whom need kidneys, and thousands die each year waiting on one.

Scientists are genetically modifying pigs so their organs are less likely to be rejected by the human immune system. 

Earlier transplant attempts — including two pig hearts and two pig kidneys — were short-lived and involved very sick patients.

But researchers have begun shifting toward testing pig organs in patients who are generally healthy. Stewart, for example, had kidney failure caused by high blood pressure but otherwise had no serious health conditions.

It can take up to seven years for folks with Stewart's blood type to find a matching kidney. And after two years on dialysis, he applied to be part of Mass General’s program.

Since the surgery, Stewart said he has been able to ease back into work and has even visited his former dialysis clinic to encourage other patients.

He told The Associated Press that he wanted to “let everyone know I’m doing all right and maybe kind of give some people some hope.”

Riella said both Stewart and Andrews required some minor changes to their anti-rejection medications, but so far, their transplanted kidneys are functioning well.

Riella said it’s far too early to know how long pig kidneys might last.

“A year, hopefully longer than that – that’s already a huge advantage,” he said.

More information

The National Kidney Foundation has more on xenotransplantation, the transplantation of living cells, tissues or organs from one species to another.

SOURCE: The Associated Press, Sept. 8, 2025