Gene-edited pig kidney supported a human for 271 days and didn’t block later transplant, case report finds

A gene-edited pig kidney kept a human patient off dialysis for 271 days before it was removed and later replaced with a donated human kidney, according to a case report published Thursday in The Lancet. The result is the strongest evidence yet that porcine kidney transplants may be able to serve as a bridge to a later human transplant, rather than only as short-lived proof-of-concept procedures.

The report’s significance goes beyond the length of time the kidney worked. Researchers said the xenotransplant — an organ transplant from one species to another — provided prolonged kidney support without clinically significant allosensitization or zoonotic infection. In plain terms, it did not appear to meaningfully complicate the patient’s later human kidney transplant by triggering an important immune response against future donors, and the report found no evidence of animal-to-human infection.

The first-in-human bridge procedure was performed Jan. 25, 2025, at Massachusetts General Hospital under expanded access, also known as compassionate use. The recipient was publicly identified by the hospital and in press reports as Tim Andrews, a New Hampshire man who had been on dialysis for more than two years. He also had type O blood, which can make finding a compatible human kidney more difficult.

The pig kidney came from eGenesis, which has developed gene-edited porcine kidneys designed to reduce immune incompatibility and infection risk. According to hospital statements and press coverage, the transplanted kidney provided 271 days of dialysis-free support before it was removed Oct. 23, 2025, after its function declined. Andrews then resumed dialysis and later received a deceased-donor human kidney in January 2026.

Multiple news outlets, including The Associated Press, described the 271-day run as a record for an engineered pig kidney in a living human recipient.

The Lancet report said the patient experienced early cellular rejection, meaning immune cells began attacking the transplanted organ, but that episode resolved with treatment. Later, however, the kidney developed worsening microvascular injury — damage to the organ’s smallest blood vessels — that progressed to thrombotic microangiopathy, a serious clotting-related condition that can impair kidney function.

That later decline did not fit neatly with the most familiar form of antibody-mediated rejection. The paper said the injury occurred despite a negative donor-specific crossmatch, a test used to look for harmful immune reactions against a donor organ. The findings support the possibility that late xenograft injury may involve mechanisms beyond conventional antibody-mediated rejection, though the case report does not settle that question.

That matters because kidney failure patients often spend years waiting for a transplant. More than 100,000 people in the United States are on the transplant waiting list, and kidneys account for the largest share of that demand. For many patients, the alternative is long-term dialysis, which can keep people alive but is burdensome and does not replace normal kidney function.

This case suggests a pig kidney may be able to buy meaningful time for at least some patients until a human organ becomes available. That would mark a different role for xenotransplantation from the field’s earlier, more limited demonstrations of short-term organ function.

Pig-to-human kidney transplants had previously shown that engineered organs could function in the near term, but mostly over days or weeks. This case extends that evidence into months. It also arrives as the field moves from isolated emergency-style procedures toward more formal testing. In September 2025, the Food and Drug Administration cleared eGenesis’ kidney program to move toward a multicenter clinical trial, signaling a shift from one-off expanded-access cases to structured study.

The case report is still just that: a single case. But it offers a clinically important proof point. A pig kidney supported one patient for most of a year, was removed after declining function, and did not appear to block a later human transplant through a clinically significant immune response or detected animal-to-human infection.

At the same time, the report underscores what researchers still need to learn. The main unanswered issue is not whether a pig kidney can work at all, but how long it can remain viable and what causes late injury when early rejection has been controlled. Those are questions formal trials will need to answer.