A patient with end-stage renal disease who received a gene-edited pig kidney lived without dialysis for 271 days before successfully receiving a human kidney transplant, marking the first reported case of transitioning from a xenotransplant to a human kidney transplant.
Dr. Leonardo Riella and his research team at Massachusetts General Hospital and Brigham (MGB) announced the milestone on the 4th in the medical journal The Lancet, stating that Tim Andrews, 66, who had been living with a pig kidney transplanted in January 2025, became the first patient to receive a human kidney transplant this past January.
Following the human kidney transplant, a 231-day follow-up of Andrews showed no evidence of "sensitization," a condition that increases the likelihood of the immune system attacking the transplanted organ.
The research team noted this is the longest reported survival period without dialysis after a pig-to-living-human xenotransplant, as well as the first case of transitioning from a xenotransplant to a human kidney transplant. They stated that this demonstrates the potential for pig kidneys to serve as a long-term "bridge" providing renal function for patients awaiting human kidney donors.
The greatest hurdle in the field of organ transplantation is the shortage of donor organs.
Kidney xenotransplantation—transplanting gene-edited pig kidneys to prevent acute rejection—is being researched as a solution to the shortage of human kidneys.
However, the research team pointed out that remaining challenges include how long transplanted pig kidneys can function, whether there is a risk of transmitting infections from pigs to humans, and whether the immune response to the pig kidney causes enough "sensitization" to affect a subsequent human kidney transplant.
The research team transplanted a gene-edited pig kidney on January 25 of last year into Andrews, who was suffering from end-stage renal disease, faced a long expected wait for a kidney from a deceased donor, and had no suitable living donors available.
The transplanted pig kidney was gene-edited to remove major carbohydrate xenoantigens, inactivate porcine endogenous retroviruses, and insert seven human genes.
Monitoring of renal function, rejection, antibodies, and pig-derived microbes after the transplant revealed that the kidney functioned immediately. Although a T-cell-mediated rejection was identified on the 14th day post-transplant, it was resolved with treatment, allowing the patient to remain free of dialysis for 271 days.
However, the research team noted that after about six months, a bacterial infection developed, prompting a reduction in immunosuppressive therapy. Subsequently, microvascular inflammation developed in the pig kidney, which progressed to thrombotic microangiopathy, eventually causing the loss of the graft function and requiring the removal of the kidney.
Eighty-two days after the pig kidney was removed, Andrews received a human kidney from a deceased donor. The new kidney functioned immediately, and a subsequent 231-day follow-up showed no evidence of sensitization that would increase the likelihood of the immune system attacking the human kidney.
The research team explained that this case demonstrates how pig kidney xenotransplantation can support renal function without long-term dialysis, serving as a bridge for patients awaiting human kidney transplants.
They added that because microvascular injury progressed to thrombotic microangiopathy and led to the loss of pig kidney graft function, there is a need to improve future immunosuppressive strategies, pig gene editing, and methods for monitoring patient status.
Dr. Riella stated, "Our goal is to utilize xenotransplantation using gene-edited pig kidneys as a bridge therapy to help patients waiting for human kidneys escape dialysis, and ultimately, once safety and persistence are confirmed over the long term, to use it as an independent treatment."
(Photo: Provided by The Lancet, Leonardo Riella et al., Yonhap News)
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