Doctors Take Another Step Toward Animal-to-Human Organ Transplants With the First Pig Kidney Transplant

The experimental procedure was done on a man experiencing end-stage kidney failure last week who had been on the transplant waiting list for two years

Doctors in scrubs gathered around a surgery table
Surgeons perform the pig kidney transplant. The surgery took place last week, and the patient is recovering well and is expected to be discharged from the hospital soon. Massachusetts General Hospital

For the first time, doctors have transplanted a pig kidney into a living human patient. Researchers hope that one day, organs from non-human animals can help address the shortage of organs available for transplant.

The patient, Richard Slayman of Massachusetts, received the experimental treatment because he was suffering from end-stage kidney failure. The four-hour surgery took place on March 16 at Massachusetts General Hospital, and Sleyman is recovering well and is expected to be discharged from the hospital soon, according to a statement from the hospital.

“This is wonderful news, and it’s great to see it move into the clinic,” Jayme Locke, an abdominal transplant surgeon at the University of Alabama at Birmingham who was not involved in Slayman’s surgery, tells Wired’s Emily Mullin.

Doctors will need to now wait and see how Slayman's body responds to the transplant in the long-term. Parsia Vagefi, who is chief of transplant surgery at UT Southwestern Medical Center and was not a part of the recent procedure, tells Mike Stobbe of the Associated Press (AP) that the surgery is “a big step forward,” but that studies with more patients at different medical centers would be needed before the treatment becomes commonly available.

“Everyone is watching this case very closely,” Vagefi says to the Wall Street Journal. “We have to see how this patient does.”

Organs for transplants are in high demand in the United States. More than 100,000 people are on the national transplant waiting list; more than 88,000 of whom need a kidney transplant. In 2023, surgeons performed 46,000 transplants of all kinds—and almost 16,000 kidney transplants—but 17 patients still die in the U.S. each day waiting for a transplant.

To address this shortage, scientists have been exploring transplanting organs from animals into humans. Two very ill patients have received pig heart transplants, but both lived for less than two months after the surgery, per Wired. And a monkey that received a pig kidney transplant lived for two years, researchers reported last October.

With such transplants, scientists need to reduce the risk that the human host rejects the donor organ or becomes infected. In this most recent procedure, researchers used CRISPR-Cas9 gene-editing technology to remove pig genes that provoke a negative response in humans and to add human genes that would make the kidney more compatible, according to a statement from the Harvard Medical School.

They also inactivated pig viruses that could have infected the recipient and made 69 genomic edits in total. Similarly edited kidneys were used in last year’s study in monkeys.

Slayman is also receiving drugs to prevent his immune system from attacking the kidney, per the medical school’s statement. He has type 2 diabetes and high blood pressure and had previously received a kidney transplant. But after five years, that kidney started to fail, requiring him to go on dialysis and regularly go to the hospital to address complications.

Slayman waited on the transfer list for a second kidney for two years, per the Wall Street Journal. He was “never really going to get one,” Mike Curtis, CEO of eGenesis, the company that genetically edited the pig kidney, tells Wired. “He was going to spend the rest of his life on dialysis.”

The FDA approved the one-time experimental procedure for Slayman under a compassionate-use protocol for people with life-threatening conditions and no alternative treatment options. Tatsuo Kawai, a Harvard Medical School surgeon who led the procedure, says in the school’s statement that they are hoping the transplanted kidney lasts for more than two years. That could allow Slayman time to receive another human kidney transplant.

“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 says in the hospital’s statement.

The FDA has said that individual procedures like the one on Slayton don’t replace the need for a formal clinical trial, the Wall Street Journal notes.

A larger supply of organs for transplant could also reduce existing disparities in access to kidney transplants, but the cost tied to Slayman’s procedure was “enormous,” Winfred Williams, a Harvard Medical School doctor and Slayman’s nephrologist, says in the school’s statement.

“I think it really has staying power, and it’s going to really revolutionize the field and hopefully offer organs to all those in need,” Locke says of animal-to-human transplants to Wired.

Get the latest stories in your inbox every weekday.