Will pig kidneys end the suffering of kidney failure patients forever?
The field of xenotransplantation achieved two consecutive milestones in the past two years that are considered the most significant in its modern history, moving from performing the first transplant of a genetically modified pig kidney into a living human in 2024 to recording the longest survival of an animal organ inside a human body, lasting 271 days, in 2025. Both procedures were carried out by medical teams from Massachusetts General Hospital, affiliated with Harvard University in the United States, as part of scientific efforts aimed at addressing the severe shortage of human organs available for transplantation in the U.S.
Medical reports stated that the first recipient of this type of procedure was Richard Slayman, a 62-year-old from Massachusetts, who suffered from chronic kidney failure after a human kidney transplanted into him in 2018 gradually lost function. Surgeons at Massachusetts General Hospital performed the pig kidney transplant on him on March 16, 2024, using the CRISPR gene-editing technology to introduce multiple genetic modifications, making the organ more compatible with the human body and less susceptible to immune rejection. According to the hospital, Slayman recovered well in the initial weeks and no longer required dialysis, before passing away on May 11 of the same year, approximately two months after the surgery. The hospital confirmed that there were no indicators linking his death to the transplanted organ itself.
Key milestones in this medical journey from 2024 to the present include:
* The first transplant of a pig kidney into a living human in March 2024 in patient Slayman, following previous failed experiments involving genetically modified pig hearts and kidneys that lasted only short periods.
* A woman from Alabama surviving for 130 days with a pig kidney earlier in 2025, before the organ’s function began to decline.
* Tim Andrews, a 67-year-old from New Hampshire, surpassing that record with a survival period of 271 days, which stands as the current global record.
The Massachusetts General Hospital team explained that Andrews, who had suffered from diabetes since the 1990s progressing to end-stage kidney failure, underwent the transplant in January 2025 as part of an experimental study supervised by the hospital in collaboration with biotechnology company eGenesis. The transplanted kidney underwent 60 genetic modifications aimed at reducing the likelihood of immune rejection.
Reports indicated that Andrews faced difficulty finding a matching blood type, which led him to volunteer for the experimental study after improving his physical fitness to become eligible. The transplanted kidney was removed from him on October 23, 2025, after its function began to decline, and he returned to dialysis while remaining on the national kidney transplant waiting list. His medical team described Andrews as a “selfless medical pioneer and an inspiration” to patients with kidney failure.
Reports noted that more than 100,000 people in the United States are currently waiting for an organ transplant, most of them needing kidneys, while thousands of patients die annually before a suitable donor becomes available. In June 2025, the Massachusetts General Hospital team performed a third pig kidney transplant on another patient from New Hampshire, who remains in good condition. Meanwhile, companies eGenesis and United Therapeutics are preparing to launch broader clinical trials for pig kidney transplants.
The experiences of Solomon and Andrews together show that scientists are now drawing on accumulated lessons from each new case, whether in selecting the healthiest suitable patients or in developing genetic modifications to organs, bringing xenotransplantation one step closer to becoming a practical therapeutic option that could help alleviate the chronic shortage of human organs available for transplantation.
