A woman at Massachusetts General Hospital is now living with a genetically edited pig kidney for more than nine months, marking a new milestone in xenotransplantation. The 285-day mark, reached as of Thursday, eclipses the previous record of 271 days held by Tim Andrews. The procedure was performed on November 22 of last year, and the patient has not required dialysis since the operation.
The organ was developed by eGenesis, a Cambridge, Massachusetts-based biotech firm. The company utilized CRISPR gene-editing technology to modify the pig kidneys, aiming to prevent immediate immune rejection and minimize the risk of transmitting porcine viruses to human recipients.
The need for such alternatives is critical. In the United States, more than 95,000 people are on the waitlist for a kidney, yet fewer than 28,000 transplants were performed in 2025. Most patients endure three to five years on dialysis—a grueling treatment requiring four-hour sessions three times a week that can damage blood vessels over time—while awaiting a human donor organ.
Mike Curtis, CEO of eGenesis, highlighted the disparity between waiting lists and donor availability. “Patients’ health gets worse the longer they’re on dialysis, and their odds of getting a human transplant aren’t rising fast enough to meet their declining health,” Curtis said. He noted that the previous record holder, Andrews, experienced a “radical improvement” in his overall health while on the pig kidney compared to remaining on chronic dialysis.
This latest patient is the fifth individual to receive an eGenesis kidney through the FDA’s expanded access pathway, which allows seriously ill patients to use experimental treatments when no adequate alternatives exist. Andrews received his transplant in January 2025 but had the organ removed in October due to declining function; he subsequently returned to dialysis before receiving a human kidney transplant in January.
In a paper published Thursday in The Lancet, the surgical team detailed that Andrews’ pig kidney eventually failed due to thrombotic microangiopathy, a condition involving tiny blood clots forming within the transplanted organ. Researchers are now using these insights to adjust the immunosuppressant medications and dosing schedules for future recipients.
Looking ahead, the FDA has approved eGenesis to conduct a formal clinical trial involving up to 33 patients aged 50 to 70 with kidney failure. However, that trial is not scheduled to begin until 2027. In the interim, the company plans to continue performing transplants under the expanded access pathway, with its next objective being a pig kidney survival time of one year.
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