Tim Andrews lives nine months with genetically modified pig kidney

Tim Andrews, a 66‑year‑old from New Hampshire who developed end‑stage kidney disease from type 2 diabetes, became the first living patient to survive nine months without dialysis after receiving a genetically modified pig kidney. The operation took place in the United States in January 2025 and was carried out by a team from the Mass General Brigham academic centres and hospitals.

From transplant to bridge to human graft

Doctors removed a kidney from a Yucatan miniature pig and used CRISPR technology to delete key pig genes while inserting human‑compatible proteins. The edited organ was intended as a temporary “bridge” while Andrews waited for a donor kidney from a human.

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After roughly six months, vascular damage emerged inside the pig kidney, leading to a gradual loss of function. In the weeks that followed, surgeons explanted the xenograft and performed a conventional human kidney transplant, restoring normal renal performance. The whole sequence lasted 271 days – the longest dialysis‑free interval recorded after a pig‑to‑human kidney transplant in a living patient.

During the nine‑month bridge, Andrews described a return to everyday activities. In a televised CNN documentary he called the transplant a “miracle” and remarked, “I was alive, and I hadn’t been in a long time.” He also said, “I was able to cook, vacuum and take long walks with my dog Cupcake.”

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

Dr Leonardo Riella, lead author, Centre for Transplantation Sciences, Mass General Brigham, via The Lancet

Dr Riella added that xenotransplantation could initially serve as a bridge to human donation and, if long‑term safety is proven, might eventually become a destination therapy in its own right.

Scientific and regulatory backdrop

The procedure builds on an earlier United States case in 2024, when another living patient received a pig kidney at Massachusetts General Hospital. That recipient survived 52 days before dying of unrelated heart complications, illustrating both the promise and the challenges of the approach.

In the United Kingdom, Dr Rommel Ravanan, chief medical officer for NHS Blood and Transplant and a consultant nephrologist, noted that the United States and China have reported several comparable transplants since 2022. He told the Press Association that advances in genetic mapping and CRISPR “genetic scissors” now enable teams to “knock out” pig genes, making the human body less able to recognise the organ as foreign.

“Public surveys have shown most, but not all, people in the UK are supportive of the idea of lifesaving animal to human transplants.”

Dr Rommel Ravanan, via Press Association

Ravanan emphasized that public acceptance rises when safety and effectiveness are demonstrated, and he cautioned that “there is still a very long way to go before these kinds of transplants could become an everyday reality.” He also linked the urgency of new therapies to the record‑high transplant waiting list in the UK, urging more people to join the NHS Organ Donor Register.

The Department of Health and Social Care‑sponsored advisory group of experts has already presented recommendations to ministers on the UK’s response to pig organ transplants. According to Ravanan, those recommendations – covering regulation, oversight, ethics, animal welfare and research – have been accepted, laying groundwork for potential future trials.

Safety checks and research implications

Researchers confirmed that no pig‑derived viruses or other pathogens were detected at any stage of Andrews’ treatment, a critical safety checkpoint for any xenotransplant programme. The study’s authors argued that the findings support pig kidney transplantation as a viable bridge for patients facing long waits for human organs, while also highlighting the need for further investigation into durability and long‑term immunological outcomes.

“The patients are the true pioneers here. By stepping forward and being willing to participate in these early‑stage studies, they are advancing the science,” Dr Riella said in the Lancet article. “Without their trust and courage, we would not be able to do what we do.”

What comes next?

While the United Kingdom currently has no clinical trials for xenotransplantation, regulators have begun examining how such procedures could be integrated into the NHS framework. The accepted advisory recommendations suggest that policy, ethical oversight and animal‑welfare considerations will be addressed before any trial launches.