Pig kidney xenotransplantation offers a bridge for patients awaiting human donor kidneys

In January 2026, Tim Andrews, who had received a genetically edited pig kidney in January 2025, became the recipient of a human kidney. A new Mass General Brigham paper, published in The Lancet, details Andrews' experience and how xenotransplantation could bridge the gap between end-stage kidney failure and a human transplant, allowing a patient to forgo dialysis in the meantime. Authors report that Andrews, who was 66 years old at the time of xenotransplantation, successfully lived with the genetically edited kidney for 271 days-during which he did not need dialysis-before receiving a human kidney from a donor. His case represents the longest dialysis-free survival following porcine kidney xenotransplantation in a living human and the first transition to human kidney transplantation.

The organ shortage is the greatest crisis we have right now in transplantation. 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. 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."

Leonardo Riella, MD, PhD, lead author, Center for Transplantation Sciences and the Division of Nephrology, Mass General Brigham

The world's first porcine kidney xenotransplant to a living human recipient occurred in 2024 at Massachusetts General Hospital, with the patient surviving 52 days before death from cardiac causes unrelated to the transplant. No previous studies have documented xenograft survival beyond two months, a successful "bridge" to receipt of a human organ, or the mechanisms leading to late xenograft failure in living recipients.

Andrews received the genetically engineered pig kidney under an FDA Expanded Access Investigational New Drug application. He was then monitored for kidney function, rejection, antibody development, and potential pig-to-human infection. The kidney functioned immediately. An early episode of T-cell-mediated rejection resolved with treatment, no pig pathogen transmission was detected, and the patient was able to go without dialysis for 271 days.

After approximately six months, immunosuppression was reduced in the setting of infection. The xenotransplant subsequently developed microvascular injury and inflammation that progressed to organ failure. The patient then received a deceased-donor human kidney, with immediate graft function and no evidence of sensitization during follow-up.

The findings illustrate both the promise and areas for improvement for xenotransplants as a bridge for patients awaiting human kidneys. Importantly, the microvascular injury to the porcine kidney has implications in the development of immunosuppressive strategies, donor genetic engineering, and monitoring in future clinical transplantation studies.

"Mass General Brigham has a strong history of kidney transplantation, beginning with the first-ever live donor kidney transplant in 1954," said senior author Tatsuo Kawai, MD, PhD, director of the Legorreta Center for Clinical Transplantation Tolerance at Mass General Brigham. "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 patients are the true pioneers here," added Riella. "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."