A leading surgeon conducting a clinical trial of transplanting pig kidneys into living people has said they could one day outperform kidneys from human donors.
Dr. Robert Montgomery, director of the NYU Langone Transplant Institute, said the first transplant trial has already been held, and another is expected to take place in January. Six patients are initially expected to receive pig organs, which have had their genes edited in 10 places to reduce rejection by the human body.
If the US Food and Drug Administration (FDA) gives approval, the study will be expanded to include 44 more transplants.
An approach called xenotransplantation aims to address the shortage of human organs.
In the UK alone, more than 12,000 people have died or been taken off the transplant waiting list in the last 10 years before receiving a new organ, according to the National Blood and Transplant Service.
Participants in the new study are either not eligible for a human kidney transplant or are on a waiting list to receive one, but they are thought to be more likely to die or remain unreplanted within five years than to receive one.
“The truth is that there will never be enough human organs,” Montgomery told the Guardian.
He speaks from experience. He is not only a pioneering transplant surgeon and one of Time Magazine's Most Influential People of 2025but he inherited a heart condition called dilated cardiomyopathy, which killed his father and brother. After Montgomery suffered seven cardiac arrests, one of which led to a month-long coma, he I myself received a heart transplant in 2018.
“I think everyone really knows that we have a terrible problem with organ rationing because there is such a supply shortage. But unless you have been in the shoes of someone waiting for a transplant, you don't fully understand how unlikely it is that you will get a transplant on time,” he said.
Montgomery pioneered new approaches to increasing the supply of human organs, including domino kidney transplant. In this situation, a living donor whose kidney is incompatible with the expected recipient is matched with another patient, whose incompatible donor is then matched with another patient and so on, creating a chain of donors and recipients that increases the availability of compatible organs.
Montgomery was also a leader in using organs from donors with hepatitis C, treating recipients with drugs to clear the resulting infection, and even accepting a hepatitis C-positive heart for his own heart transplant.
But he said other approaches are needed.
“Having spent my career trying to incrementally increase the number of human organs available, I realized that we just haven’t made that much progress, not in a meaningful way,” he said. “And any progress we made was kind of undone by the ever-increasing number of people waiting for a transplant.”
While the idea of xenotransplantation has been around for decades, Montgomery said recent developments have proven crucial, including the possibility of creating gene-edited pigs. “There's been a lot of jokes about xenotransplantation, as if it's just around the corner, and it's a very long turnaround,” he said. “But suddenly we were in it.”
In 2021, Montgomery performed the world's first gene-edited pig-to-human organ transplant. Although the kidney recipient was a brain-dead person, Montgomery said it was an important step, showing the organs were not immediately discarded and providing important safety data that opened the door for use in living people.
Montgomery said it is possible that pig organs will eventually become more suitable for transplantation than human organs, with the possibility of further gene editing to reduce the likelihood of rejection. “At some point they can get better because we can continually modify them to make them better, which is not possible with a human organ,” he said.
Researchers Research including Montgomery showed that transplanting a pig's thymus, an organ involved in the development and selection of immune cells, along with a kidney can also improve tolerance, increasing the possibility of eventually reducing or even eliminating the need for anti-rejection drugs. “We haven’t reached that goal yet, but that’s why we’re doing these studies,” he said.
Although the new clinical trial is the first to use xenotransplantation, pig organs have previously been transplanted into a handful of people, most of whom were already seriously ill.
Some of these patients subsequently had to have their organs removed and others diedalthough not necessarily due to complications associated with transplantation. However, Montgomery said there are two living pig kidney recipients who still have organs left.
He said the kidneys and heart are promising organs for xenotransplantation, while the lungs are more challenging. “[And] liver, whether it will work is still a mystery,” he said.
He said he wouldn't mind getting the pig's heart himself.
“Next time, if I stay healthy and alive, I will definitely think about it,” he said. “I have children who have the same genetic condition as me, and I, of course, constantly think about them and want them to have more opportunities than my father, my brother or I had.”
