A man who received a genetically edited pig kidney last year has become the first patient to successfully progress from that procedure to a full human kidney transplant, according to a new study from researchers at Massachusetts General Hospital and Harvard Medical School.
Tim Andrews, 66, of New Hampshire, received the pig kidney in January 2025 after years on dialysis for end-stage kidney disease. He lived with the organ for 271 days without needing dialysis, before it began to fail and he received a donated human kidney in January this year. The findings were published on 3 September in The Lancet.
Pig Kidney Transplant: How did the patient fare with the pig kidney?
Andrews received the kidney under an expanded access programme authorised by the US Food and Drug Administration, which allows patients with serious, life-threatening conditions to access experimental treatments outside standard clinical trials. According to the study’s authors, the organ functioned immediately after transplantation. An early episode of rejection driven by T-cells was successfully treated, and no transmission of pig pathogens to the patient was detected throughout his monitoring.
Pig Kidney Transplant: Why did the pig kidney eventually fail?
Around six months after the transplant, doctors reduced Andrews’s immunosuppressive medication because of an infection, a decision that researchers say ultimately contributed to the organ’s decline. The xenograft went on to develop microvascular injury and inflammation that progressed into organ failure, prompting the need for a replacement kidney.
Pig Kidney Transplant: What happened when he received the human kidney?
Andrews received a kidney from a deceased donor in January 2026. According to the study, the new organ began functioning immediately, and follow-up monitoring found no evidence that his body had developed heightened sensitisation, a complication that can sometimes make patients harder to match with future donor organs after receiving an animal transplant.
Pig Kidney Transplant: Why do researchers consider this case significant?
The study’s authors say Andrews’s case represents the longest documented dialysis-free survival following a pig-to-human kidney transplant, and the first instance of a patient successfully transitioning from a xenotransplant to a human donor organ. Lead author Leonardo Riella, of the Center for Transplantation Sciences and the Division of Nephrology at Mass General Brigham, said the findings speak to one of the most urgent problems facing the field. “The organ shortage is the greatest crisis we have right now in transplantation,” he said.
Pig Kidney Transplant: How does this fit into the broader story of pig kidney transplants?
Andrews was the fourth person in the world to receive a genetically edited pig kidney, and the second such transplant carried out at Massachusetts General Hospital following the world’s first procedure of its kind in March 2024. That earlier patient, Rick Slayman, survived for 52 days with his pig kidney before dying of cardiac causes unrelated to the transplant. The pig organs used in these procedures have typically been genetically modified using CRISPR gene-editing technology to remove harmful pig genes, add certain human genes, and reduce the risk of infection being passed between species.
Pig Kidney Transplant: What happens next for xenotransplantation research?
Researchers say Andrews’s experience strengthens the case for xenotransplantation as a viable bridge therapy, potentially allowing patients with end-stage kidney disease to avoid dialysis while they wait for a suitable human donor to become available.
Several members of the research team disclosed financial ties to eGenesis, the biotechnology company that provided the genetically edited pig kidney, as well as other transplant-related firms, relationships the authors say are common in translational medical research of this kind. With more than 100,000 people in the United States currently on transplant waiting lists, researchers say further studies will be needed to determine how widely such xenotransplant bridging could eventually be applied.
