Genetically Modified Pig Kidney Keeps Patient Dialysis Free For Nine Months

A genetically modified pig kidney successfully kept a 66-year-old man alive and off dialysis for 271 days, marking the longest dialysis-free survival for a porcine-to-human transplant. The landmark case, detailed in the medical journal The Lancet on September 3, 2026, demonstrates the clinical viability of xenotransplantation as a temporary bridge to conventional human organ transplantation.

Tim Andrews, who suffered from end-stage kidney disease, eventually transitioned back to dialysis briefly before receiving a compatible human kidney. This sequence represents the first documented case where an animal organ successfully sustained a living patient until a human donor organ became available, offering a potential pathway to address the chronic global shortage of transplantable organs.

Andrews received the experimental organ on January 25, 2025, at Massachusetts General Hospital under the Food and Drug Administration's Expanded Access Investigational New Drug pathway. Prior to the surgery, he had spent more than two years on dialysis, a grueling regimen made more difficult by his O blood type, which severely limited his chances of finding a compatible human donor.

The pig kidney began functioning immediately upon transplantation, allowing Andrews to halt dialysis entirely. Although he experienced an early episode of organ rejection, doctors successfully treated it, and no pig-to-human pathogens were detected during his monitoring. The organ ultimately functioned for nine months, far exceeding the previous record of 52 days set during the world's first living pig kidney transplant in 2024.

To prevent the human immune system from immediately rejecting the foreign tissue, scientists performed 69 precise genetic edits on the donor pig's genome. These alterations removed specific pig genes known to trigger hyperacute immune reactions in humans, while inserting human genes designed to regulate blood clotting and immune responses.

researchers inactivated endogenous pig retroviruses within the donor animal's DNA to eliminate the risk of cross-species viral transmission. This extensive genetic engineering is critical because the human immune system is naturally primed to attack foreign biological material. Without these modifications and a tailored regimen of immunosuppressive drugs, a porcine organ would fail within minutes of reperfusion.

Despite the initial success, the pig kidney was not a permanent solution. Around the six-month mark, clinical monitoring revealed signs of microvascular injury, blood clots, and localized inflammation within the organ's blood vessels. This progressive damage gradually compromised the kidney's filtration capacity.

By January 2026, after a full year of carrying the organ, the transplant had progressed to failure, requiring Andrews to return to dialysis. However, the nine-month dialysis-free window provided invaluable data for researchers studying the long-term behavior of xenografts. Understanding these late-stage failure mechanisms is essential for scientists working to extend the lifespan of animal-derived organs.

The success of the procedure highlights the potential of xenotransplantation to alleviate a severe public health crisis. In the United States alone, nearly 90,000 people are currently on the waiting list for a kidney transplant, with approximately 11 individuals dying each day while waiting for a compatible organ.

Dr. Leonardo Riella, the lead author of the study and a senior investigator at the Center for Transplantation Sciences at Mass General Brigham, emphasized the scale of the problem. "The organ shortage is the greatest crisis we have right now in transplantation," Riella stated. He explained that while transplantation is the optimal treatment for end-stage renal failure, the supply of human organs remains critically inadequate. "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."

For Andrews, the experimental surgery and subsequent human transplant have resulted in a dramatic physical recovery. Prior to the xenotransplant, years of dialysis had severely degraded his quality of life and dampened his appetite. Today, he is highly active, participating in swimming, kayaking, and short bicycle rides.

Reflecting on his journey, Andrews recalled the despair he felt before the procedures. "I went from thinking I had months, maybe a year, because I just felt so bad," he told The New York Times. The successful transition to a human kidney has profoundly altered his outlook. "When you say 'stop and smell the roses,' that's my life now," Andrews said. "I look at everything and go 'wow.'"

Researchers at Mass General Brigham and other institutions are currently analyzing the tissue samples from Andrews' pig kidney to map the precise cellular pathways that led to the microvascular injury at six months. These findings will guide the development of next-generation genetic edits and more targeted immunosuppressive therapies.

While the FDA continues to evaluate xenotransplantation on a case-by-case basis under expanded-access protocols, larger clinical trials will be required to establish standardized safety profiles. Dr. Riella praised the courage of patients like Andrews, noting, "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."