Genetically Modified Pig Kidney Helps Man Live 271 Days Without Dialysis, Sets Transplant Milestone

A groundbreaking development in transplant medicine has demonstrated how genetically modified animal organs could one day help patients survive while waiting for a human donor. In the United States, a 66-year-old man with end-stage kidney disease lived for 271 days without dialysis after receiving a genetically edited pig kidney.

The case, reported by researchers at Mass General Brigham and published in The Lancet, is being described as a major milestone for xenotransplantation, the use of animal organs in human patients. It is also the first documented case in which a patient successfully moved from a pig kidney transplant to a human kidney transplant.

A Kidney From a Genetically Modified Pig

The patient, Tim Andrews, had severe kidney failure associated with type 2 diabetes. Like many people with end-stage kidney disease, his long-term options were limited by the shortage of suitable human donor organs.

In January 2025, doctors at Massachusetts General Hospital transplanted a genetically engineered pig kidney into Andrews. The procedure was performed under an FDA Expanded Access Investigational New Drug application, allowing the medical team to closely monitor the experimental treatment.

Unlike a conventional pig organ, the transplanted kidney had undergone genetic modifications designed to make it more compatible with the human body and reduce the possibility of immune rejection and other complications.

The kidney began functioning immediately after transplantation. Andrews was subsequently able to remain free from dialysis for 271 days, establishing the longest reported period of dialysis-free survival following a pig kidney transplant in a living human at the time of the study.

Nine Months Without Dialysis

For patients with advanced kidney failure, dialysis can become a regular and demanding part of life. Treatment requires repeated visits to a medical facility or the use of specialized equipment to remove waste and excess fluid from the blood.

The pig kidney offered Andrews a temporary alternative while he waited for a human organ.

Doctors monitored him for several factors, including kidney function, rejection, the development of antibodies and possible transmission of infections from the animal organ. An early episode of T-cell-mediated rejection was successfully treated. Researchers also reported that they found no evidence of transmission of pig pathogens.

The kidney eventually developed microvascular injury and inflammation, which progressed and caused the organ to fail. After approximately six months, immunosuppression had been reduced because of an infection, a factor that researchers are examining as part of their analysis of the organ's eventual failure.

From Pig Kidney to Human Kidney

The most significant part of Andrews' case came after the pig kidney stopped functioning.

After the experimental organ was removed, Andrews returned to dialysis for a period before receiving a deceased-donor human kidney in January 2026. The human kidney began functioning immediately, and follow-up showed no evidence that the previous pig transplant had made him sensitized against the human donor organ.

This transition is particularly important because researchers see genetically modified pig organs not necessarily as replacements for human organs, but initially as a temporary bridge.

Under such a model, a patient could receive a pig kidney, avoid or reduce dialysis, and remain in better condition while waiting for a suitable human donor.

Why the Breakthrough Matters

Human kidneys remain in short supply compared with the number of people who need transplants. Patients can spend years waiting for a suitable organ, with outcomes influenced by factors such as blood type, medical condition and donor availability.

Researchers believe genetically engineered pigs could eventually provide an additional source of transplantable organs. However, the technology is still experimental, and much more research is required before it can become a routine treatment.

The Andrews case also provides scientists with important information about what needs to improve. The late microvascular damage and inflammation observed in the pig kidney could help researchers refine genetic modifications, immune-suppressing treatments and methods for detecting problems earlier.

The achievement follows an earlier milestone in 2024, when the world's first genetically engineered pig kidney was transplanted into a living human at Massachusetts General Hospital. That recipient survived 52 days, with death ultimately attributed to cardiac causes unrelated to the transplant. Before Andrews' case, no living-human pig kidney transplant had demonstrated survival beyond two months or successfully served as a bridge to a human kidney.

A Possible New Path for Transplant Medicine

The 271-day milestone does not mean pig kidneys are ready to replace human donor organs. It is a single-patient experience and still involves significant medical challenges.

Nevertheless, Andrews' journey demonstrates something scientists have been working toward for decades: an animal organ can perform kidney functions inside a human for an extended period and potentially keep a critically ill patient away from dialysis until a human organ becomes available.

For transplant researchers, the biggest promise may therefore lie not simply in making pig kidneys last longer, but in developing a dependable bridge-to-transplant strategy. If future studies confirm safety and improve long-term organ function, genetically modified animal organs could eventually become an important tool for addressing the persistent shortage of human donor kidneys.

Note: As of September 4, 2026, a subsequent report says another patient has surpassed the 271-day mark, so Andrews' case is best described as the record-breaking 271-day milestone reported in this study and the first successful transition from a pig kidney to a human kidney.