Pig Kidney Transplant Achieves Historic Milestone

A genetically modified kidney from a pig named Wilma has remarkably allowed a 66-year-old man with kidney failure to live for nine months. This unprecedented achievement acted as a crucial “bridge” to a subsequent human transplant.

Tim Andrews, suffering from end-stage kidney disease due to type 2 diabetes, found himself in a dire situation; he had only a 9% chance of receiving a human kidney within the next five years. The situation was even grimmer, with over a 40% risk of dying or being removed from the waiting list altogether.

Kidney transplants are known to offer the best outcomes in terms of survival and quality of life for those with severe kidney disease. Yet, it’s a stark reality that the demand for human organs far outstrips the supply.

In an operation conducted in the U.S., surgeons successfully transplanted a genetically engineered kidney from Wilma, a Yucatan miniature pig, into Andrews. The kidney had been modified to ensure compatibility with his immune system.

This kidney performed impressively, keeping Andrews free from dialysis for an astonishing nine months—the longest such record to date—before it began to fail, leading him to receive a kidney from a deceased human donor. This marked the first instance of utilizing a pig’s kidney as a temporary bridge to a human transplant.

Details about this groundbreaking development, which offers hope to many facing kidney failure, were shared in the Lancet medical journal.

Andrews, a resident of New Hampshire, referred to the pig kidney transplant as a “miracle,” stating, “I was alive, and I hadn’t been in a long time.” He spoke about being able to cook, vacuum, and enjoy long walks with his dog, Cupcake.

While the concept of transplanting genetically modified pig organs has been suggested as a solution to the organ shortage for years, the first attempt at a pig kidney transplant in a living individual back in 2024 only lasted 52 days before the patient succumbed to unrelated heart issues. Prior studies had not documented any successful xenograft survival beyond two months.

Before the transplant in January 2025, Wilma underwent 69 edits to her genome. These modifications were intended to avoid potential viruses harmful to humans and to enhance organ compatibility, thereby lowering the chances of immune rejection.

The transplant team at Mass General Brigham, a non-profit academic healthcare system in Massachusetts, reported that Andrews successfully thrived with the genetically altered kidney for 271 days before transitioning to a human kidney from a donor.

His case showcases the longest dialysis-free survival following a pig kidney transplantation, as well as being the world’s first move to human kidney transplantation, according to the team.

Dr. Leonardo Riella, from the Center for Transplantation Sciences and the Division of Nephrology at Mass General Brigham, emphasized that the organ shortage poses a significant challenge in transplantation today. He remarked that while transplantation is the best treatment for those with severe kidney disease, there simply aren’t enough human organs available promptly.

“We envision that xenotransplantation could bridge this gap—initially to help patients off dialysis while they await a human donor kidney, and possibly, as we confirm long-term safety, as a viable treatment option in its own right,” Riella added.

About six months after the transplant, damage in the blood vessels of the pig kidney led to its failure, necessitating its removal nine months post-transplant.

After being back on dialysis for a while, Andrews received a functioning kidney from a deceased human donor, which performed well during the six-month follow-up period.

No new antibodies against human tissue were found, indicating that the pig kidney had not complicated the success of the human kidney transplant. Additionally, no pig-related viruses or pathogens were detected at any stage.

The team noted, however, that this involved a single patient without a comparison group, and it’s crucial to understand that the results may reflect specialized patient selection and care that might not be widely accessible.

Further clinical trials, similar to Andrews’ involvement, will be necessary. Still, this success paves the way for considering pig kidney transplants as a temporary solution for others facing lengthy wait times for human kidneys.

“These patients are the true pioneers,” Riella remarked. “Their willingness to take part in early-stage studies is pushing the boundaries of science. Without their trust and bravery, none of this would be possible.”