Pig Kidney Transplant Keeps Patient Alive for Record 271 Days

A 66-year-old patient has set a medical milestone by surviving for 271 days with a genetically modified pig kidney, the longest duration ever recorded for such a procedure. The patient, Tim Andrews, who suffered from end-stage kidney disease caused by type 2 diabetes, underwent the experimental xenotransplantation at Massachusetts General Hospital in January 2025. The procedure was intended as a temporary bridge to sustain his life while he awaited a compatible human donor organ.

This case, detailed in a paper published in The Lancet on September 3, 2026, represents a significant advancement in the field of xenotransplantation. By successfully keeping a patient off dialysis for nine months, the surgery provides critical evidence that animal-to-human organ transplants could eventually serve as a viable solution to the global shortage of human donor kidneys. The patient has since transitioned to a successful human kidney transplant, marking the first time a patient has moved from a pig organ to a human one.

The kidney used in the procedure was sourced from a Yucatan miniature pig that had been engineered with 69 distinct genomic modifications. These genetic edits were essential to humanize the organ, effectively stripping away biological markers that would otherwise trigger an immediate immune response in a human recipient. Furthermore, the modifications were designed to disable latent porcine viruses embedded within the pig's DNA, mitigating the risk of cross-species pathogen transmission.

Without these sophisticated genetic interventions, the human immune system would typically destroy foreign tissue within minutes of transplantation. The success of the graft for over eight months suggests that these modifications were effective in delaying acute rejection. Researchers at Mass General Brigham, who conducted the surgery, noted that no pig viruses or other pathogens were detected in the patient throughout the duration of the transplant, addressing a primary safety concern in the field of xenotransplantation.

Despite the initial success, the procedure was not without significant clinical hurdles. Approximately six months post-surgery, the transplanted kidney began to show signs of vascular damage, which eventually progressed to organ failure. Doctors were forced to manage early signs of rejection through careful adjustments to the patient's immunosuppressive medication regimen, highlighting the ongoing complexity of maintaining long-term compatibility between porcine organs and human physiology.

Following the failure of the pig kidney in October 2025, the organ was removed, and Andrews returned to short-term dialysis for 82 days. This period of dialysis was necessary to stabilize his condition before he could receive a human donor kidney in January 2026. The transition from the experimental pig organ back to a human donor kidney is a critical development, demonstrating that xenotransplantation does not necessarily preclude a patient from receiving a standard human transplant later.

Dr. Leonardo Riella, the study’s lead author and medical director for kidney transplantation at Mass General Brigham, emphasized that the current organ shortage is the most pressing crisis in modern transplantation. With over 100,000 people in the United States currently awaiting kidney transplants, the gap between supply and demand remains a life-threatening issue. Xenotransplantation is being explored as a potential strategy to bypass the long waiting lists that often force patients to remain on dialysis for years.

"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," Dr. Riella stated. The researchers believe that by providing a temporary lifeline, these procedures can improve the quality of life for patients who would otherwise face the grim survival statistics associated with long-term dialysis.

Reflecting on his experience, Tim Andrews described the experimental procedure as a "miracle" that provided him with a renewed sense of hope. "I was dying," Andrews recalled in a report published by The New York Times. "I figured, if I'm going to die, I might as well do something for humanity and be part of this experiment." His willingness to participate in the study was instrumental in gathering the data required to advance the field.

Dr. Riella praised the courage of patients like Andrews, noting that their participation is essential for scientific progress. "The patients are the true pioneers here," he said. "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." This collaborative effort between clinicians and patients continues to shape the future of transplant medicine.

The success of the 271-day survival period provides a foundation for future research, though experts caution that significant challenges remain. While this case demonstrates the potential for pig kidneys to function in humans, it also underscores the need for further studies to understand the long-term durability of these organs. Other similar transplants have been reported in the US and China since 2022, including a 2024 case at Massachusetts General Hospital where the patient survived for 52 days before succumbing to unrelated heart issues.

As the medical community continues to refine the genetic modifications and immunosuppressive protocols, the focus will likely shift toward increasing the duration of graft survival. While there are currently no active clinical trials for similar procedures in the UK, regulators globally are closely monitoring these developments to establish the necessary safety frameworks for future human trials. The case of Tim Andrews serves as a landmark reference point for the potential of xenotransplantation to transform the treatment of end-stage renal failure.