On March 16, Massachusetts General Hospital (MGH) achieved another medical milestone by performing the first successful pig-to-human kidney transplant.
Using a genetically modified organ made by Massachusetts-based biotech eGenesis, Rick Slayman, a 62-year-old patient with end-stage kidney disease, underwent a four-hour xenotransplantation surgery, or the transfer of organs in a human from nonhuman sources, the hospital announced in a statement.
With more than 100,000 people in the US on waitlists, experts said the success of the procedure laid grounds for optimism of more similar organ transplants.
But on May 7, Slayman died. He was facing cardiovascular issues, which ended his life only 51 days after the groundbreaking procedure. At the end of May, Healthcare Brew spoke with two experts involved with the transplant about the implications of Slayman’s death on the future of this kind of xenotransplantation.
“We developed such a strong relationship with him over these past two months, and we were communicating with him multiple times a day,” Leonardo Riella, medical director of the kidney transplant program at MGH, who was part of the surgical team, told Healthcare Brew. “So on a personal level, I was heartbroken.”
Slayman had Type 2 diabetes and hypertension, and had been on dialysis for seven years before he received a transplant from a human donor in December 2018, also at MGH, according to the hospital. But five years later, the kidney started to fail, and Slayman started up dialysis again in May 2023.
Riella said that the longer patients stay on dialysis, the more cardiovascular disease they develop—the issue that led to Slayman’s death.
“There was no indication that the kidney transplant contributed to his passing, and we have a blood test on the day of his passing showing that his new kidney was working well and maintaining a normal balance of all the minerals in the body,” Riella said.
In fact, the surgery had gone well. During the operation, the physicians saw Slayman’s kidney turn “purple-reddish” and immediately start producing urine: both great signs that don’t always happen in human-to-human transplants, according to Riella.
The kidney had 69 genetic edits to make it compatible for a human body, according to MGH, and showed a two-year post-surgery survival rate during testing on nonhuman primates.
“Our ultimate goal is long-term outcomes that treat and provide options for patients in organ failure broadly,” eGenesis CEO Mike Curtis told Healthcare Brew.
The hospital was able to do the procedure thanks to the FDA’s compassionate use expanded access protocol, which gives patients who have life-threatening conditions access to treatments that don’t have FDA approval.
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Joseph Vassalotti, chief medical officer at the National Kidney Foundation and clinical professor at Icahn School of Medicine at Mount Sinai, said xenotransplantation should only be offered to people who have exhausted current kidney transplant options and are struggling with dialysis.
“At this point, xenotransplantation cannot be used broadly for Americans living with kidney failure,” Vassalotti wrote in an email on Tuesday. “There remain several challenges, including immunologic barriers [and] infectious disease risks, and there may be unrecognized risks, as should be expected with any new therapy,” he said.
But Vassalotti said the public interest around xenotransplantation “should give Americans living with kidney failure hope,” adding that he had “deep gratitude” to Slayman.
Curtis said he now has even more hope than before, in part due to what the medical teams learned from the procedure.
At MGH, Riella said the team is doing analysis on research samples that were collected over the last two months to learn as much as they can about Slayman’s immune response and kidney function. He also experienced an acute cellular rejection episode in the kidney on the eighth day after the transplant, which taught the care team about how to adjust post-op medication for future patients.
“Like all transplants, allotransplants and now xenotransplants, the long-term challenge is maintaining compatibility and avoiding infection because all these patients will be immunosuppressed,” Curtis said. “The surgeons wanted to get kind of a jump on that, and so they reduced the immune suppression. We did see a little bit of rejection, but then we increased immune suppression drugs, and the reduction went away and the kidney recovered. And that was a huge learning [experience].”
Going forward, Curtis said eGenesis is exploring more surgeries through the expanded access process, and the company is also working with the FDA to initiate a clinical trial next year.
“Over the past five or six years, there’s been a really productive collaboration between us, the transplant community, FDA regulators, and it all really culminated in Rick’s transplant. What it really shows us is, in patients like Rick, there is a path forward now. It’s not 10 years from now. It’s now,” Curtis said. “That’s why I have so much hope.”