Tim Andrews lived with a genetically modified pig kidney for a record 271 days before receiving a human organ at Mass General Brigham. The milestone case highlights xenotransplantation as a potential bridge for patients facing severe donor shortages while illuminating biological hurdles that researchers must navigate.
The field of xenotransplantation reached a notable milestone when a kidney transplanted from a pig functioned inside a patient for nearly nine months. Tim Andrews, a 67-year-old patient from New Hampshire living with end-stage kidney disease and diabetes, received the experimental organ on January 25, 2025 (as reported by KSL). The procedure made him one of the world’s first recipients of a genetically engineered animal organ.
The 271-Day Bridge: From Dialysis to Xenotransplantation
For Andrews, the pig kidney operated as a crucial lifeline. Facing a lengthy waitlist for a human donor—with estimates suggesting it could take seven years—he turned to the experimental therapy after experiencing severe complications on dialysis, including a heart attack six months after starting regular filtration treatments.
“It takes a toll on you emotionally and physically; you just get exhausted and I got sick. I was throwing up all the time.”
Tim Andrews, patient
Following the xenotransplant, Andrews experienced an immediate shift in his daily well-being. He recalled feeling clear-headed and energized compared to the persistent fatigue of dialysis (noted in KSL coverage). The clinical team at Mass General Brigham emphasized that such procedures demonstrate how animal organs can serve as a viable bridge until a human transplant becomes available.
Navigating Rejection and Securing a Human Donor
Maintaining the xenograft required an intensive medical protocol. Andrews took 52 pills a day to manage his immune response alongside the pig kidney, which he named Wilma. Over the course of nine months, however, the organ began showing signs of rejection. Despite adjustments to his immunosuppressant regimen by Dr. Leonardo Riella and the medical team, the filters sustained irreversible damage (according to hospital disclosures).
In October, doctors removed the xenograft, returning Andrews to a short period of dialysis. Mike Curtis, president and CEO of eGenesis—the biotech company that supplied the donor pig (detailed by regional reporting)—noted that scientists monitored the gradual rejection process for months and gained valuable data from biopsies to help tune future immunosuppression protocols.
The interim period on dialysis proved temporary. Near midnight on January 12, Mass General Brigham notified Andrews that a near-perfect human match had been found. Following a three-hour transplant procedure on January 13, Andrews became the first person in the world to transition from an experimental pig kidney to a human organ.
“I’m the first one that went across the bridge. … I’m the only person in the world that’s ever had a pig kidney and then had a human kidney after it.”
Tim Andrews, patient
Addressing the Global Organ Shortage
The broader implications of Andrews’ case point toward persistent systemic shortages in organ donation. Frontiers in Nephrology notes that chronic kidney disease affects over 850 million individuals globally, creating a gross mismatch between patients needing grafts and the limited supply of eligible human donors. In the United States alone, approximately 100,000 people wait for a kidney at any given time, while only 25,000 transplants occur annually (highlighted by public broadcasting reports).
Genetically engineered pigs remain the preferred animal donors due to their physiological similarities and rapid reproduction rates. Modern genetic engineering utilizes techniques such as GalTKO knockouts and modifications to limit complement system activation and blood clotting (detailed in academic literature). Furthermore, biotech firms like eGenesis are tracking how patients develop antibodies after xenograft removal, confirming through recent clinical updates that recipients can subsequently receive human organs safely (reported by specialized life sciences journalism).
Mass General Brigham and Future Clinical Outlook
For medical teams at Mass General Brigham, the successful human transplant following an experimental xenograft answers key safety questions regarding post-transplant antibody production. Dr. Leonardo Riella emphasized that even when animal organs function strictly as a temporary measure, they offer a vital alternative to the steep physical decline associated with long-term dialysis.
As Andrews prepares to return to his New Hampshire home, researchers continue to refine genetic modifications and immunosuppressive regimens to improve the durability of future xenografts. Clinical trials and preclinical research aim to transform nephrology standards and expand treatment options for thousands of patients currently waiting on transplant lists.
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