A genetically modified pig kidney has kept a 66-year-old American man with end-stage kidney disease off dialysis for nine months before he successfully received a human kidney transplant in what doctors described as a world first.
The patient, Tim Andrews, received the experimental pig kidney at Massachusetts General Hospital in Boston in January 2025 after developing kidney failure linked to type 2 diabetes.
Andrews had been undergoing dialysis for more than two years and had a low likelihood of receiving a suitable human donor kidney. Doctors therefore used the genetically engineered pig kidney as a temporary “bridge” while he waited for a human organ.
The kidney, obtained from a genetically modified Yucatan miniature pig, began functioning immediately after the transplant. It produced urine and removed waste from Andrews’ bloodstream, allowing him to stop dialysis.
The organ remained functional for 271 days, or almost nine months, making it the longest period a pig kidney had functioned in a living human recipient at the time.
Doctors initially managed an episode of rejection by intensifying Andrews’ immunosuppressive treatment. However, after about six months, the kidney developed damage to its blood vessels, which eventually led to organ failure.
The pig kidney was removed in October 2025, after which Andrews returned to dialysis for 82 days.
He subsequently received a kidney from a deceased human donor in January 2026. The human kidney began functioning successfully, and doctors reported no evidence that the previous pig transplant had prevented or complicated the human transplant.
Researchers said the case provides early evidence that genetically modified animal organs could potentially serve as temporary support for patients who face long waits for human donor organs.
The experimental kidney had been genetically modified to reduce the likelihood of rejection and lower the risk of infection from pig-derived viruses. The patient was also given immunosuppressive medication to help his body tolerate the transplanted organ.
The researchers cautioned, however, that the treatment remains experimental and that the experience of one patient cannot establish its long-term safety or effectiveness.
The findings, published in The Lancet, represent a significant development in xenotransplantation — the transplantation of organs between different animal species — amid a severe global shortage of human donor kidneys.
Researchers hope that continued advances in genetic engineering and transplant medicine could eventually make pig kidneys a viable option for patients who cannot obtain human donor organs, either temporarily or potentially for longer periods.
