A leading surgeon behind a clinical trial of transplanting pig kidneys into living humans has said they could one day be superior to those from human donors.
Dr Robert Montgomery, the director of NYU Langone’s Transplant Institute, said the first transplant of the trial had already been carried out, with another expected to take place in January. Six patients are initially expected to receive the pig organs, which have been gene-edited in 10 places to reduce rejection by the human body.
Should the US Food and Drug Administration (FDA) give approval, the trial will be expanded to involve 44 further transplants.
The approach, called xenotransplantation, is aimed at solving the shortage of human organs.
According to the NHS Blood and Transplant, in the UK alone more than 12,000 people have died or been removed from the transplant waiting list over the past 10 years before receiving a new organ.
Participants in the new trial are either ineligible for human kidney transplantation or on a waiting list for such an organ but thought to be more likely to die, or remain un-transplanted, within five years than receive it.
“The truth is that there’s just never going to 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 2025, but he has inherited a heart condition called dilated cardiomyopathy, which killed his father and brother. After Montgomery experienced seven cardiac arrests – one of which resulted in a month-long coma – he received a heart transplant himself in 2018.
“I think everybody really knows that we have a terrible problem in terms of rationing organs because there’s such a scarcity of supply. But unless you’ve walked in the shoes of somebody who’s waiting for a transplant, you don’t really fully understand how unlikely it is that you’re going to receive a transplant in time,” he said.
Montgomery has pioneered new approaches to increasing supply of human organs, including domino-paired kidney transplants. In this situation, a living donor whose kidney is incompatible with their expected recipient is matched with another patient, whose own incompatible donor is then matched to another patient and so on, creating a chain of donors and recipients that increases the availability of compatible organs.
Montgomery has also been a leader in the use of organs from donors with hepatitis C, treating recipients with medication to clear the resulting infection, and even accepted a hepatitis C–positive heart for his own heart transplant.
But he said other approaches were needed.
“Having spent a career trying to increase incrementally the number of human organs available, I realised that we just weren’t making that much progress, not in a meaningful way,” he said. “And any progress we made was kind of deleted by the ever-expanding number of people who are waiting for transplants. ”
While the idea of xenotransplantation has been around for decades, Montgomery said recent developments had proved pivotal – including the ability to create gene-edited pigs. “There were all these kind of jokes about xenotransplantation, like it’s just around the corner and it’s an awfully long corner,” he said. “But suddenly we’re in it.”
Montgomery carried out the world’s first gene-edited pig-to-human organ transplant in 2021. While the recipient of the kidney was a brain dead individual, Montgomery said it was an important step, showing the organs were not immediately rejected and providing crucial safety data that had opened the door for use in living people.
Montgomery said it was even possible that pig organs could eventually become superior to human ones for transplants, with the possibility for further gene edits to make rejection less likely. “They could be superior at some point because we can constantly modify them to make them better, where you can’t do that with a human organ,” he said.
Studies by researchers including Montgomery have shown that transplanting the pig’s thymus – an organ involved in the development and selection of immune cells – along with the kidney can also improve tolerance, raising the possibility of eventually reducing or even eliminating the need for anti-rejection drugs. “We’re not there yet, but that’s why we’re doing those studies,” he said.
While the new clinical trial is a first to be carried out with xenotransplantation, pig organs have previously been transplanted into a handful of humans, most of whom were already severely ill.
Some of these patients subsequently had to have the organs removed and others have died, albeit not necessarily from complications relating to the transplant. However, Montgomery said there were two living recipients of pig kidneys who still had the organs.
He said kidneys and hearts were promising organs for xenotransplantation, while lungs were more complicated. “[And] the liver, it’s still a mystery of whether it’s going to work,” he said.
He said he would not be adverse to receiving a pig heart himself.
“Next time around, if I continue to be healthy and alive, I certainly would consider it,” he said. “I’ve got kids who have the same genetic disease that I have and I certainly think about them all the time, and want them to have more options than my dad had, or my brother or I had.”
