A leading US transplant surgeon has said gene-edited pig kidneys could one day prove superior to human donor organs, as the first clinical trial involving living patients gets under way.
Dr Robert Montgomery, director of the Transplant Institute at NYU Langone, said the first transplant in the trial had already been carried out, with another expected in January. Six patients are initially set to receive pig kidneys that have been gene-edited in 10 places to reduce the risk of rejection.
If approved by the US Food and Drug Administration (FDA), the trial will later be expanded to include a further 44 patients.
The technique, known as xenotransplantation, is intended to address the global shortage of donor organs.
In the UK, more than 12,000 people have died or been removed from transplant waiting lists over the past decade before receiving an organ, according to NHS Blood and Transplant.
Participants in the trial are either ineligible for a human kidney transplant or are on a waiting list but considered unlikely to receive an organ within five years.
“The truth is that there’s just never going to be enough human organs,” Montgomery said.
His interest in the issue is deeply personal. Montgomery, named one of Time magazine’s most influential people of 2025, has a hereditary heart condition that killed his father and brother. After suffering seven cardiac arrests, including one that left him in a month-long coma, he received a heart transplant in 2018.
He said the scale of the organ shortage was not fully understood by those who had never faced life on a transplant waiting list.
Montgomery has spent much of his career attempting to increase the supply of human organs. His work includes pioneering domino-paired kidney transplants, which link incompatible donor-recipient pairs into chains that allow more patients to receive suitable organs.
He has also led efforts to use organs from hepatitis C–positive donors, treating recipients after surgery to clear the infection. Montgomery himself accepted a hepatitis C–positive heart for his own transplant.
Despite these advances, he said they were not enough.
“Any progress we made was overtaken by the ever-growing number of people waiting for transplants,” he said.
Xenotransplantation has been discussed for decades, but Montgomery said recent breakthroughs, particularly in gene-editing technology, had transformed the field.
He carried out the world’s first gene-edited pig-to-human organ transplant in 2021, using a brain-dead recipient. The procedure showed the kidney was not immediately rejected and provided safety data that paved the way for trials in living patients.
Montgomery said pig organs could eventually outperform human ones, as they can be continually modified to reduce rejection.
Researchers have also found that transplanting a pig’s thymus alongside the kidney may improve immune tolerance, potentially reducing or even eliminating the need for long-term anti-rejection drugs. He said more research was needed before this could become routine.
Pig organs have previously been transplanted into a small number of severely ill patients. Some later required removal of the organs, and others died, though not always as a result of the transplant. Two recipients of pig kidneys are still living with the organs, Montgomery said.
He added that kidneys and hearts appeared the most promising for xenotransplantation, while lungs and livers remained more complex.
Montgomery said he would consider receiving a pig heart himself in the future.
“I’ve got children with the same genetic condition I have,” he said. “I want them to have more options than my father, my brother, or I ever had.”
