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US approves first human trials for pig kidney transplants
09 Sep 2025

The US Food and Drug Administration (FDA) has approved the first human trial of pig kidney transplants.

The groundbreaking study will be conducted by eGenesis, a biotech company that specializes in developing gene-edited pigs for organ transplantation.

This is a major milestone in xenotransplantation, the process of transplanting organs from one species to another.

CRISPR makes pigs' organs more compatible with human recipients
Modification process

eGenesis uses a gene-editing technology called CRISPR to make pigs' organs more compatible with human recipients.

The process involves knocking out a specific gene responsible for producing a carbohydrate known as alpha-gal.

This is important because, without this modification, the human body would reject a pig organ almost immediately after transplantation.

Previous xenotransplantation procedures in the US
Past trials

In the past, there have been a few xenotransplantation procedures in the US, including pig kidney transplants at NYU Langone and pig heart transplants at the University of Maryland School of Medicine.

However, these were not part of standard clinical trials but were done under special rules for compassionate use of experimental therapies for patients in dire situations.

Over 100,000 people waiting for an organ donation in US
Organ shortage

In the US alone, over 100,000 people are waiting for an organ donation. Of these, a whopping 86% need a kidney.

The average wait time for a kidney is three to five years at most centers.

However, Stewart's case was different as he has type O blood which can take up to 10 years to get a donor kidney in the US.

67-year-old Tim Andrews is longest-surviving recipient of pig kidney
Previous transplants

In March 2024, 62-year-old Rick Slayman became the first patient at Mass General—and the world's first living recipient—to undergo a transplant with a genetically edited pig kidney.

He died two months later from cardiac complications unrelated to the transplanted organ.

In January, 67-year-old Tim Andrews received a similar pig kidney transplant at Mass General. The organ continues to function, making him the longest-surviving recipient of a pig kidney to date.

In June, another US resident received a pig kidney transplant
New development

On June 14, doctors at Massachusetts General Hospital performed their third experimental pig kidney transplant.

The recipient, Bill Stewart, had been on dialysis for over two years due to his kidneys functioning at just 10% to 15% of their normal capacity.

Stewart is gradually returning to work and outdoor activities after the successful procedure.

"There's so few of us who have done this, and they're writing the protocol as we go, so to speak. But I'm feeling good," he said.

What do the trials mean?
Future prospects

The FDA-approved trials will allow researchers to study this technology in a broader population.

Mike Curtis, the president and CEO of eGenesis, said these studies are crucial to understanding how this technology performs in different patients.

United Therapeutics plans to begin its trial this year with up to 50 patients while eGenesis hopes to treat its first patient before the year ends.

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