Genetically Modified Pig Kidney Sets New Human Survival Record, Keeps Patient Off Dialysis for Nine Months
A genetically modified pig kidney has achieved a major milestone in human transplantation, functioning inside a patient for 271 days without dialysis before the patient successfully received a human donor kidney. The case, reported by researchers at Massachusetts General Hospital and published in The Lancet, represents the longest documented dialysis-free survival following a pig-kidney transplant in a living human.
The patient was Tim Andrews, who was 66 when he underwent the experimental procedure in January 2025. He had end-stage kidney disease associated with diabetes and faced a very low likelihood of receiving a conventional human kidney within a reasonable period. The experimental pig organ gave him a way to remain free from dialysis while waiting for a human donor.
What makes the case particularly significant is what happened next. In January 2026, after the pig kidney had functioned for 271 days, Andrews received a deceased-donor human kidney. The human organ began functioning immediately, and follow-up showed no evidence that the earlier pig transplant had sensitized his immune system against the human kidney.
Researchers describe this as the first successful transition from a pig-kidney transplant to a human kidney transplant. Instead of attempting to make an animal organ a permanent replacement immediately, the strategy could eventually use genetically modified pig kidneys as a temporary “bridge” that keeps patients healthy and off dialysis until a suitable human organ becomes available.
The pig kidney itself was extensively genetically engineered. Such modifications are intended to make the organ more compatible with the human immune system, reduce the risk of rejection and address concerns about pig-derived infections. The broader program has involved organs supplied by the biotechnology company eGenesis, whose researchers have used gene-editing techniques including CRISPR.
The kidney initially worked well. Andrews was able to remain dialysis-free for the entire 271-day period, demonstrating that a genetically engineered pig kidney can provide substantial renal function in a living human for many months. Earlier attempts had generally resulted in substantially shorter survival.
The transplant was not completely free of complications. Andrews experienced an episode of T-cell-mediated rejection early after transplantation, but it responded to treatment. Later, immunosuppression was reduced because of an infection, after which the pig kidney developed microvascular injury and inflammation that eventually progressed to organ failure.
Importantly, investigators found no evidence of transmission of pig pathogens during the xenotransplantation period. Continuous monitoring for infection is a major part of developing animal-to-human transplantation because genetically modified organs could theoretically introduce infectious agents into recipients.
The case therefore provides researchers with more than a survival record. It offers evidence that xenotransplantation could potentially be incorporated into the existing transplant system rather than necessarily replacing human organs altogether.
That possibility is important because the shortage of human kidneys remains severe. Many patients with end-stage kidney disease spend years waiting for a transplant, while dialysis carries substantial physical and logistical burdens. Researchers hope that genetically modified pigs could eventually provide a controlled, renewable source of organs.
The breakthrough also comes after several years of rapid progress in xenotransplantation. In March 2024, Mass General surgeons performed the world’s first genetically edited pig-kidney transplant into a living human. That kidney came from a pig with 69 genetic modifications, representing an earlier major step toward overcoming the biological barriers between pigs and humans.
Scientists are now trying to determine why these organs eventually fail and how genetic engineering and immunosuppressive treatment can be improved. The microvascular injury observed in Andrews’ kidney is particularly important because it could help researchers redesign future pig organs and develop better methods of controlling immune and vascular complications.
The development is already moving beyond a single experimental patient. Mass General and its collaborators have performed additional pig-kidney transplants, while researchers and biotechnology companies are preparing larger clinical studies. Reports indicate that eGenesis is planning a multicentre trial involving as many as 33 kidney patients, with the aim of determining whether the approach can become a practical clinical therapy.
There is still an important limitation: one patient’s 271-day survival does not establish that genetically modified pig kidneys are ready to replace human kidneys routinely. Larger studies must determine long-term safety, durability, rejection rates, infection risks, quality of life and survival outcomes.
Nevertheless, Andrews’ case changes the central question surrounding kidney xenotransplantation. Scientists have now demonstrated not merely that a genetically modified pig kidney can temporarily function in a human, but that it can keep a patient off dialysis long enough to serve as a bridge to a successful human transplant.
For patients trapped between progressive kidney failure and a long transplant waiting list, that could ultimately prove to be one of the most important applications of genetically engineered animal organs.
