For the first time, a person has survived 271 days - around nine months - with a pig kidney. Although the organ had to be removed after complications, after 82 days on dialysis the patient received a human donor kidney, which the body accepted without any major problems.
As the Boston research facility Mass General Brigham reports, this is the first time that a pig kidney has bridged the waiting time for a human donor kidney. Never before has a person lived so long with an animal donor kidney.
The patient, named Tim Andrews, was 66 years old at the time of the pig kidney transplant and had end-stage kidney disease due to type 2 diabetes, as Leonardo Riella's group from Massachusetts General Hospital in Boston reported in the journal "The Lancet." Andrews therefore had no chance of receiving a human donor kidney in the foreseeable future due to a long waiting list.
Those involved decided on a xenotransplantation, i.e. the insertion of an organ from a foreign species. “Our vision is that xenotransplantation can help close this gap - initially as a bridge to free patients from dialysis while they wait for a human donor kidney,” explained Riella.
If the long-term safety and durability of pig kidneys in the human body is proven, they could possibly even remain in patients permanently, says Riella. However, there is still a lot of research work to be done before then.
The first patient who had a pig kidney transplanted at Massachusetts General Hospital in March 2024 died 52 days after the transplant. The researchers emphasize that the patient died of cardiovascular disease and that his death was not related to the transplant. The pig kidney was still fully functional.
Andrews received the pig kidney in January 2025. It came from a mini pig raised free of pathogens in a special facility. 69 genetic changes were made to the pig's genome to prevent the human immune system from recognizing the kidney as a foreign body and attacking it.
Nevertheless, 14 days after the transplant, the treating doctors registered a mild rejection reaction that was triggered by T cells, which are part of the human immune system.
After three months, doctors reduced the dosage of medication to suppress the innate immune system. After six months, damage to the blood vessel walls of the kidney became visible. In addition, a collection of blood in the fatty tissue around the kidney had to be surgically removed.
After 271 days the kidney failed
After about 220 days, doctors again reduced the suppression of the immune system due to the patient's bacterial infection, which led to inflammation in small blood vessels. This ultimately led to the kidney failing, which had to be removed after 271 days. Until then, the patient did not need dialysis.
After another 82 days of dialysis treatment, Andrews received a human donor kidney in January 2026. Six months after the transplant, doctors said there were no signs of rejection. They conclude that the pig kidney did not add any complexity to human kidney transplantation.
There was no evidence that pathogens were transmitted from pigs to humans. “The absence of zoonotic infections and the transition to subsequent human kidney transplantation in this case further underline the potential of xenotransplantation as a bridging measure or long-term strategy in selected patients,” write the study authors.
Joachim Denner from the Free University of Berlin, who was not involved in the study himself, assesses the work of his US colleagues as positive: “The patient has the longest survival period to date with a functioning pig kidney.”
According to Denner, the study provides important insights into understanding the immunological rejection mechanisms in xenotransplantation. “For future studies, this could mean that more intensive immunosuppression is required, especially in the early phase after transplantation,” says Denner. It is also important that there was no evidence of transmission of swine viruses to the patient over the entire observation period of around nine months.
Moritz Schmelzle from the Hannover Medical School (MHH), who was also not involved in the study, sees the transplantation of a pig kidney as a promising approach to bridging the waiting time until a human organ is transplanted.
“Due to the very high number of patients with end-stage kidney disease and the resulting need for dialysis, kidney xenotransplantation is a particularly relevant area of application for this technology,” says Schmelzle. However, the extent to which pig kidney transplantation is actually a medical and economic alternative to longer-term dialysis treatment needs to be investigated in further studies.
In the long term, it is hoped that the quality, functional duration and safety of xenogeneic organs will be comparable to those of human donor organs, says Schmelzle. This could help reduce the number of patients on the waiting list for a human organ donor.
