Pig Kidney Transplant Still Functioning After Record 285 Days in Patient

A woman who received a genetically modified pig kidney at Massachusetts General Hospital on November 22 last year has now lived 285 days without needing dialysis, surpassing the previous record of 271 days set by another recipient, Tim Andrews.

The organ was engineered by Cambridge, Massachusetts-based biotech company eGenesis, which used Crispr gene-editing technology to remove pig genes capable of triggering an immune response and to insert several human genes, reducing the risk of rejection and of pig viruses being transmitted to the patient.

An alternative to dialysis

Most people awaiting a kidney transplant wait three to five years, relying on dialysis in the meantime — a process that typically requires three four-hour sessions a week and can gradually damage blood vessels. eGenesis CEO Mike Curtis notes that patients' health tends to decline faster than their chances of receiving a human organ improve.

The woman is the fifth patient to receive an eGenesis kidney under the FDA's expanded access pathway, which allows people with serious or life-threatening conditions to try experimental treatments when no good alternative exists. Andrews' case illustrates that a pig kidney may serve as a temporary bridge: he received his in January 2025, had it removed last October after declining function, returned to dialysis, and received a human kidney transplant this January. A study published in The Lancet found that his transplant failed due to thrombotic microangiopathy — the formation of tiny blood clots within the organ — findings eGenesis is now using to adjust immunosuppressant dosing for future recipients.

Kidneys remain the most in-demand organ, with more than 95,000 people on the US waiting list, while fewer than 28,000 kidney transplants were performed nationwide in 2025. The FDA has cleared eGenesis to run a larger trial involving up to 33 patients starting in 2027, and the company plans to continue additional transplants through the expanded access pathway in the meantime. Its next milestone goal is keeping a transplanted pig kidney functioning for a full year.