(CNN) — Doctors have performed the first transplant of a genetically modified kidney from a pig into a living human, they announced Thursday.
The four-hour surgery was performed Saturday at Massachusetts General Hospital, which was also the first hospital to perform a kidney transplant in 1954.
The patient, Rick Slayman, a 62-year-old manager with the Massachusetts Department of Transportation who had been diagnosed with end-stage kidney disease, is recovering well and expected to be discharged from the hospital soon.
Doctors said Thursday that they thought his new kidney could last years but also acknowledged that there are many unknowns in animal-to-human transplants.
In a written statement provided by the hospital, Slayman said he had been a patient in the hospital’s transplant program for 11 years. He received a kidney from a human donor in 2018 after living with diabetes and high blood pressure for many years. That kidney began to show signs of failure five years later, and he resumed dialysis in 2023.
When he was diagnosed with end-stage kidney disease last year, he said, his doctors suggested that he try a pig kidney.
“I saw it not only as a way to help me, but a way to provide hope for the thousands of people who need a transplant to survive,” Slayman said in the statement.
Doctors who were not involved in the case said the surgery represented a significant medical milestone.
“To finally see this come to fruition after years of work and collaboration is really a huge step forward and a great moment for transplant,” said Dr. Parsia Vagefi, chief of surgical transplantation at UT Southwestern Medical Center in Dallas.
‘The most beautiful kidney I have ever seen’
Dr. Tatsuo Kawai, director of the Legorreta Center for Clinical Transplant Tolerance and the surgeon who performed the operation, said the pig organ was exactly the same size as a human kidney.
When they stitched it in, connecting its blood vessels to Slayman’s, Kawai said, it immediately “pinked up” and began to make urine. The 15-member transplant team in the operating room burst into applause, he said.
“It was truly the most beautiful kidney I have ever seen,” Kawai said Thursday in a news briefing that was emotional for the doctors involved, some of whom have worked on this research for their entire careers.
One doctor choked up as he thanked the patient, his colleagues and their biotech partners. A fellow physician put a hand on his shoulder and said, “You did it.”
The need for organs far outstrips the number that are available. Every day, 17 people in the US die waiting for an organ, and kidneys are the organ in shortest supply. According to the Organ Procurement and Transplantation Network, roughly 27,000 kidneys were transplanted in 2023, but nearly 89,000 people were on the waitlist for those organs.
Experts say xenotransplants – transplants of animal organs into people – are crucial to solving the organ shortage.
“It also could be a potential breakthrough in solving one of the more intractable problems in our field, that being an unequal access for ethnic minority patients to the opportunity for kidney transplantation,” said Dr. Winfred Williams, associate chief of the Department of Nephrology at Mass General, in the news briefing.
This is the third transplant of a pig organ into a living human. The first two were hearts transplanted into living people who had run out of other transplant options. The organs were transplanted under special rules that permit compassionate use of experimental therapies for people in especially dire situations. Both patients died weeks after receiving their organs.
The researchers at Mass General Brigham said that although the latest advance was important, more research is needed – ideally a large study conducted at many hospitals – to better understand how effective pig kidney transplants may be.
“Our hope is that dialysis will become obsolete,” said Dr. Leonardo Riella, medical director of kidney transplantation at Mass General. “Dialysis will be like a ventilator for a patient with respiratory failure. You use it for a period of time, and hopefully if they’re healthy enough, they could have a more permanent solution, which could be a human transplant or a xenotransplant.”
Williams said Slayman had been his patient for more than a decade before the procedure.
He said the xenotransplant made a lot of sense for Slayman, who had “great difficulty” on dialysis. Vascular disease, diabetes and high blood pressure meant the blood vessels that that fed the dialysis machine would frequently clot, complicating treatment.
Slayman needed more and more interventions to remove the clots. He estimates that he endured 30 to 40 procedures to address the problems.
“At one point, he told me he thought he would not be able to go on. He literally said, ‘I don’t think I can go on like this. I don’t want to go on like this,’ ” Williams said.
At that point, Williams said, he began to explore extraordinary options and landed on the idea of using pig organs for Slayman.
A milestone decades in the making
The organ came from a pig that was genetically modified by a company eGenesis Bio to make it more compatible with a human. Other companies are also working to make pig tissues and organs suitable for xenotransplants.
Experiments taking blood and skin from animals and using them in humans began in the 1600s with blood and skin.
Researchers say the goal of transplanting pig kidneys to humans began to be pursued in the 1960s.
Although pig kidneys are remarkably similar to human kidneys, figuring how to prevent the human immune system from rejecting them has not been easy, they noted.
“The human immune system reacts incredibly violently to a pig organ, much moreso than to a human organ,” said Dr. Joren Madsen, director of the Mass General Transplant Center.
Madsen noted that if you gave a person the same medicines used to prevent the rejection of other human organs and tried it with pig kidneys, “that transplant would reject and turn black in minutes. Minutes.”
There are three key advances that have finally made xenotransplantation a reality, Madsen said.
First, eGenesis was able to use CRISPR-Cas9 technology to make 69 precise edits to the pig’s DNA – in some areas, snipping things out, in other spots putting things in – to prevent the human body from recognizing the pig kidneys as foreign and rejecting them. They knocked out three genes that for sugars that are expressed on the surface of pig cells that can be recognized by human antibodies and and attacked. They also used gene editing to deactivate pig retroviruses that can reawaken and infect humans.
The second: Pharmaceutical companies were able to make special monoclonal antibodies specifically tailored to prevent the rejection of pig organs.
Finally, Madsen said, they were able to test pig organs in non-human animal models to develop the best protocols to translate the technology to people.
“This successful procedure heralds a new era in medicine in which we have the potential to eliminate organ supply as a barrier to transplantation and realize our vision that no patient dies waiting for an organ,” Dr. Michael Curtis, CEO of eGenesis, said in news release.
“We are humbled by the courage and generosity of this patient, who is a true pioneer, enabling this major break-through in science and transplant medicine,” he said.
