A genetically modified kidney from a pig named Wilma has kept a 66-year-old man with kidney failure alive for a record nine months and successfully acted as a "bridge" to a human transplant in a world first. Tim Andrews suffered from end-stage kidney disease caused by type 2 diabetes and had only a 9% chance of receiving a human kidney within five years, with a more than 40% risk of dying or being removed from the waiting list. Kidney transplants offer the best chance for survival and quality of life for patients with this condition, but the demand for human organs far exceeds the supply. Surgeons in the US transplanted a kidney from Wilma, a Yucatan miniature pig, into Andrews after genetically engineering it to be compatible with his immune system. The kidney kept Andrews free of dialysis for a record nine months, the longest period ever recorded, before it began failing and he received a kidney from a deceased human donor. This was the first time a pig's kidney had been used as a temporary "bridge" to a human transplant. Details of the breakthrough, offering hope to millions of people with kidney failure, were published in the Lancet, a respected medical journal. Andrews, from New Hampshire, described the pig kidney transplant as a "miracle," saying he had not been alive for a long time. He was able to cook, vacuum, and take long walks with his dog, Cupcake, he said. Transplanting genetically engineered pig organs has long been proposed as a solution to the organ shortage. However, the first pig kidney transplant into a living person in 2024 ended after 52 days when the patient died from unrelated heart problems. No previous studies had documented xenograft (animal-to-human) survival beyond two months, according to the Lancet. Before the transplant in January 2025, Wilma had received 69 edits to her genome. Some of these were designed to prevent viruses that could be harmful to humans, while others made the organ more compatible with humans, reducing the risk of immune rejection. The team at Mass General Brigham, a non-profit academic healthcare system in Massachusetts, reported that Andrews lived with the genetically edited kidney for 271 days before receiving a human kidney from a donor. His case represents the longest dialysis-free survival following a pig kidney transplant in a living human, and the world's first transition to a human kidney transplant, the team said. Dr. Leonardo Riella from Mass General Brigham noted that the organ shortage is the greatest crisis in transplantation today. He said that while kidney transplants are the best treatment for end-stage kidney disease, there are not enough human organs available in a timely manner. "Our vision is that xenotransplantation could help address this gap—initially as a bridge to get patients off dialysis while they wait for a human donor kidney, and potentially, as we establish long-term safety and durability, as a destination therapy in its own right," Riella said. After roughly six months, damage developed in the pig kidney's blood vessels, leading to organ failure. The kidney was removed nine months after transplantation. After several months back on dialysis, Andrews received a kidney from a deceased human donor, which worked well during six months of follow-up, according to the Lancet. There were no new antibodies against human tissue detected, indicating the pig kidney had not made it harder for the human kidney transplant to work successfully. No pig viruses or other pig pathogens were detected at any point. The team cautioned that this was a single patient case with no comparison group, and the outcome might reflect careful patient selection and intensive specialist care not available elsewhere. Further clinical trials, such as the one Andrews participated in, will be needed. But the success opens the door to pig kidney transplants as a bridge for other people facing long waits for a human kidney, they said. "The patients are the true pioneers here," Riella said. "By stepping forward and being willing to participate in these early stage studies, they are advancing the science. Without their trust and courage, we would not be able to do what we do."