A man was given a genetically-modified pig kidney that enabled him to stay off dialysis for nine months in a world first.
Doctors said the animal organ was used as a temporary “bridge” while the man waited for a transplant from a human donor.
Tim Andrews, who had end-stage kidney disease, was 66 when he received the pig kidney in the United States in January 2025.
He lived successfully with the genetically-edited organ for 271 days before moving to short-term dialysis and receiving a donor human kidney.
It is the longest dialysis-free survival after a pig kidney transplant in a living human and the first transition from pig-to-human kidney transplantation, doctors have said.
The team, from Mass General Brigham academic centres and hospitals in the US, published their findings in The Lancet medical journal.
Study lead author and nephrologist Dr Leonardo Riella said: “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.”
Britain’s National Health Service (NHS) Blood and Transplant chief medical officer Dr Rommel Ravanan said that the US and China have reported several similar transplants since 2022.
“Advances in genetics technology enable teams to ‘knock out’ some of the pig genes, so the human body is less able to recognise the organ was different.
“Recent improvements in genetic mapping and the development of techniques such as CRISPR ‘genetic scissors’ have made this more possible.
“Pigs are chosen for several reasons, including that their organ size and anatomy is similar to that of humans,” he said.
The consultant nephrologist added: “It’s important to recognise that, even if shown to be effective, there is still a very long way to go before these kinds of transplants could become an everyday reality.”
Andrews had kidney failure caused by type 2 diabetes.
His temporary kidney came from a Yucatan miniature pig and was genetically engineered to be compatible with the human immune system.
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It began working immediately after transplantation.
However, after roughly six months, damage developed in the kidney’s blood vessels, which progressed to organ failure, and the pig kidney was removed.
Researchers said no pig viruses or other pig pathogens were detected at any point.
In a CNN documentary, Andrews said the pig kidney transplant was a “miracle”, adding: “I was alive, and I hadn’t been in a long time.”
Dr Riella said: “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.
“Without their trust and courage, we would not be able to do what we do.” – By Jane Kirby/PA Media/dpa
