Tim Andrews spent 271 days living with a gene-edited pig kidney before receiving a human transplant in January 2026. The case, detailed in a report published in The Lancet, marks the longest dialysis-free survival recorded after porcine kidney xenotransplantation in a living patient and the first documented transition from animal to human kidney transplantation.
From Dialysis to Xenotransplant
Andrews had been on dialysis for more than two years due to end-stage kidney disease while remaining on the transplant waiting list. He received the genetically engineered pig kidney under an FDA Expanded Access Investigational New Drug application. The organ was developed by eGenesis. Following the procedure, Andrews did not require dialysis during the entire period the porcine kidney functioned.
Medical teams monitored Andrews closely for kidney function, rejection episodes, antibody development, and potential transmission of porcine pathogens. According to the published findings, graft function remained stable for roughly six months. Researchers then reduced immunosuppression to address a nonzoonotic bacterial infection.
Graft Failure and Subsequent Transplant
Continuous monitoring eventually revealed microvascular inflammation with endothelial injury, leading to thrombotic microangiopathy. The complications caused the porcine kidney to fail, and it was surgically removed. Eighty-two days later, Andrews underwent another transplant, this time receiving a deceased-donor human kidney.
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During the 231 days of follow-up monitoring after the allotransplantation, Andrews showed no evidence of sensitization. The transplanted human kidney demonstrated immediate and sustained function. The authors noted that early cellular rejection had responded to treatment, while later graft failure appeared linked to mechanisms beyond conventional antibody-mediated rejection.
The case highlights areas requiring further investigation. “Early cellular rejection resolved with treatment, whereas later graft failure was associated with microvascular injury progressing to thrombotic microangiopathy despite a negative donor-specific crossmatch, supporting the possibility that mechanisms beyond conventional antibody-mediated rejection contributed to late graft injury,” the authors wrote.
Addressing the Organ Shortage
Leonardo Riella, MD, PhD, medical director for kidney transplantation at Mass General Brigham and lead author of the report, emphasized the broader context driving xenotransplantation research. “The organ shortage is the greatest crisis we have right now in transplantation,” he said. “We know that the best treatment option for patients with end-stage kidney disease who have developed renal failure is transplantation, but we simply don’t have enough human organs to transplant in a timely manner.”
Riella outlined a potential role for xenotransplantation in addressing this gap. “Our vision is that xenotransplantation could help address this gap—initially as a bridge to get patients off dialysis while they wait for a human donor kidney, and potentially, as we establish long-term safety and durability, as a destination therapy in its own right.”
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The approach may eventually allow some patients to avoid prolonged dialysis entirely while awaiting human donors, though this particular case did not achieve that outcome. Whether similar xenotransplant recipients would face comparable complications remains unclear without additional data from other procedures.
Tatsuo Kawai, MD, PhD, director of the Legorreta Center for Clinical Transplantation Tolerance at Mass General Brigham and lead surgeon for Andrews’ case, pointed to the institution’s historical role in transplantation advances. “Mass General Brigham has a strong history of kidney transplantation, beginning with the first-ever live donor kidney transplant in 1954,” he said. “Our findings continue that history by both furthering what we know about xenotransplants and generating knowledge that could be applied to other organ transplantation work.”
The authors acknowledged the limitations of a single-patient case report while noting its significance for future research. Riella reserved his final comment for the patients who participate in early-stage studies. “The patients are the true pioneers here,” he said. “By stepping forward and being willing to participate in these early-stage studies, they are advancing the science. Without their trust and courage, we would not be able to do what we do.”
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