The new era of animal-to-human kidney transplantation is off to a good start. On Wednesday, 62-year-old Richard Slayman, the world’s first living human recipient of a genetically modified pig kidney, was able to go home from the hospital. Slayman’s new kidney appears to be functioning as expected two weeks post-surgery.
Animal-to-human transplantation, or xenotransplantation, has become a promising avenue for addressing the long-standing shortage of donated organs, though it’s taken many decades to reach this point. Recent innovations in gene-editing technology have made it possible for scientists to create pigs that are more compatible with human biology. And the hope is that the organs from these pigs can be safely tolerated by the recipient’s immune system.
Over the past few years, there have been several early successful tests of the technology in humans. But these experiments have been largely performed on animals and people declared brain-dead, whose bodies their families have allowed to be kept mechanically alive for a time while the donated organ is monitored. In January 2022, terminally ill 57-year-old David Bennett became the world’s first living human to receive a genetically modified pig heart, but he died only two months later. Last October, the second living recipient of a modified pig heart, 58-year-old Lawrence Faucette, died a month after his procedure.
Much like Bennett and Faucette, Slayman was allowed to undergo this experimental procedure due to his limited options. He has long dealt with type 2 diabetes and hypertension and was given a typical donated kidney in 2018. By 2023, however, the kidney had begun to fail. Once he was switched to dialysis, he began to experience recurrent complications that required regular hospital visits to manage. Faced with the likely prospect of a long wait for a second human kidney, Slayman agreed to receive a pig kidney transplant instead.
The transplant was performed by doctors from Massachusetts General Hospital, who have conducted previous pig kidney experiments, using a kidney sourced from a pig developed by the biotech company eGenesis. Scientists removed three pig genes and added seven human genes to improve the pig’s compatibility. They also inactivated several porcine endogenous retroviruses, which are integrated into every pig’s genome. Some evidence has suggested that a previously undetected infection caused by the latent pig virus porcine cytomegalovirus might have contributed to the death of David Bennett.
Slayman did experience symptoms of cellular rejection eight days after the procedure, a common transplant complication. But his doctors were able to treat it with steroids and other immune-dampening drugs. So far, Slayman’s new kidney appears to be working as hoped, filtering out waste products and producing urine. And he has now recovered well enough to be sent home.
“This moment—leaving the hospital today with one of the cleanest bills of health I’ve had in a long time—is one I wished would come for many years,” Slayman said in a statement from Massachusetts General Hospital. “Now, it’s a reality and one of the happiest moments of my life.”
It will take time to know whether Slayman’s body will accept the new organ long-term. And even if this transplant is as successful as possible, larger-scale clinical trials of the technology will be needed before it could be made available to the public. Some scientists have also argued that it will take many more years before these modified pig organs can be as long-lasting as those from donor humans. But for now, there’s reason to be optimistic.