A genetically modified pig kidney kept Tim Andrews off routine dialysis for 271 days, creating a new benchmark for xenotransplantation while also highlighting unresolved safety questions. Andrews, 66, received the organ on 25 January 2025 after developing end stage kidney disease linked to type 2 diabetes. The surgical team reported in the Lancet that the graft worked immediately and sustained function until it was removed in October 2025 when signs of progressive damage became apparent.
After the pig kidney was taken out, Andrews returned to dialysis for 82 days before receiving a human donor organ in January of this year, a transplant the team reports is functioning well. Clinicians logged early immune activity against the pig kidney that responded to adjustments in medication, but around six months after implantation the organ’s blood vessels showed damage and inflammation increased, driving graft failure. The investigators said they did not detect clear antibody signals to explain that deterioration, underlining biological risks that remain unexplained.
The kidney came from a Yucatan miniature pig engineered with 69 genomic edits intended to make pig tissue less visible to the human immune system and to disable pig-borne viruses. The team removed pig-specific markers and introduced human DNA in targeted locations, a stepwise approach designed to prevent the immediate, destructive immune assault that typically ruins unmodified animal grafts.
The experiment unfolded against a severe shortage of human kidneys. In the United States about 100,000 people wait for a kidney while roughly 25,000 transplants happen each year, and more than 7,000 people sit on the UK list. Andrews had been told reaching the top of the list might take seven years, while average survival on dialysis is about five years, realities that shaped the case as a clinical bridge to a later human organ.
Researchers and clinicians framed the result as both promise and caution. Dr Leonardo Riella of Mass General Brigham said, "we are in a crisis" and added, "we are working really hard to bring hope and we truly feel that xenotransplantation can be an alternative for patients who don't have a living donor where we could potentially bypass dialysis and get them to a transplant." Andrews called the procedure "hope" and "the light at the end of the tunnel," saying it offered a chance to live without the dialysis machine.
The case establishes that an edited pig kidney can keep a patient off dialysis for many months, but it also exposes limits: unexplained vascular injury and immune responses that compromised durability. The next steps are longer, carefully monitored clinical studies and tighter oversight to track blood-vessel injury and immune markers, before the approach can be considered a routine option for people waiting for human donors.
