A Genetically Modified Pig Kidney Kept a Man Alive for a Record Nine Months, Allowing Him to Wait for a Donated Human Organ

The animal organ kept Tim Andrews off dialysis for 271 days and represents the first time a pig kidney has been used as a bridge to human organ transplantation September 11, 2026 8:00 a.m. Surgeons Leonardo Riella (left) and Tatsuo Kawai (right) talk to patient Tim Andrews after he received a genetically modified pig kidney in early 2025. Kate Flock / Massachusetts General Hospital For the first time, a genetically modified pig kidney has served as a temporary bridge to a human organ transplant, keeping a man alive and off dialysis for nine months while he waited for a human kidney to become available. Researchers describe the case in a paper published September 3 in the Lancet. The man in question is Tim Andrews, a now 68-year-old New Hampshire resident who had been suffering from end-stage kidney disease. He was on dialysis, a process that removes excess fluid and waste from the blood when the kidneys stop working properly, and his prognosis wasn’t good. But Andrews had heard that genetically modified pig kidneys were being tested in humans, so he decided to volunteer for the experimental—and risky—procedure. “I didn’t think I was going to live through it, to be honest,” he tells NBC News’ David K. Li. “But I wanted to do it for humanity. I realized, ‘OK, I’m a dead man. I’m a dead man walking.’ So, I said to myself, ‘What have I done? What have I done with my life? This is an opportunity for me to do something that most people don’t get an opportunity to do, and that’s to help humanity.’” In January 2025, surgeons at Massachusetts General Hospital in Boston transplanted a kidney from a Yucatan miniature pig into Andrews. The pig, which Andrews nicknamed Wilma, had received 69 genetic edits designed to reduce the risk of porcine virus transmission and lower the chances of Andrews’ immune system rejecting the organ, reports the Guardian’s Andrew Gregory. After recovering from the procedure, Andrews felt better than he had in years. “I could walk around,” he tells NPR’s Rob Stein. “I wasn’t tied to a machine. I wasn’t dead tired. So, for me, it was beautiful.” About six months after the transplant, Andrews developed a bacterial infection from methicillin-resistant Staphylococcus aureus (MRSA), which is resistant to many antibiotics. His doctors reduced his immunosuppression drugs, which were helping prevent his body from rejecting the foreign organ. But then the pig kidney’s blood vessels started to become damaged. Eventually, the damage escalated to organ failure. Andrews lived with the pig kidney—and was able to avoid dialysis—for a record 271 days. Though the kidney ultimately had to be removed, doctors consider the transplant overall to be a success. “He had a [pig] kidney that lasted nine months, which is mind-blowing,” lead author Leonardo Riella, who helped conduct Andrews’ surgeries and serves as medical director for kidney transplantation at Mass General Brigham, tells New Scientist’s Chris Simms. After surgeons removed the pig kidney, Andrews went back on dialysis for three months. Then, in January 2026, he received a donated human kidney. These days, he spends his time swimming, riding his bike, kayaking, fishing and soaking up life. “Every day I wake up. I’m like, [this is] another [extra] day because I should have been dead a year ago or more,” he tells NBC News, adding that he expects to live for decades. And he remains grateful to Wilma. “She saved my life,” he tells NPR News. “She was the bridge so that I didn’t die, so I got to the human kidney.” Did you know? First pig kidney transplant In March 2024, surgeons at Mass General Hospital—including Riella—transplanted a genetically modified pig kidney into a human for the first time. The patient, 62-year-old Richard Slayman, who had end-stage kidney disease, died 52 days later from seemingly unrelated cardiac issues. Technically, the pig kidney did not completely bridge the gap for Andrews. However, “it carried the majority of the waiting time the patient had to undergo before being able to receive the human organ transplant, therefore proving the concept that it is possible,” David Mulligan, a surgeon at Yale School of Medicine who was not involved with the research, tells STAT’s Eric Boodman. Since Andrews, Riella says his team has completed five additional pig kidney transplants. One patient, whose case will be described in a forthcoming paper, has already surpassed Andrews’ nine-month record, per New Scientist. Taken together, the cases suggest that briefly having a pig organ in their bodies doesn’t affect how patients later react to human organ transplants. “Right now, we don’t think there’s any downside of having a pig kidney followed by a human kidney, but when we started this, we had no idea that that would be true,” says Mike Curtis, president and CEO of eGenesis, the company developing the genetically modified pig organs used at Mass General Brigham and helping fund the research, to the New York Times’ Roni Caryn Rabin. Some researchers consider xenotransplantation, or the use of animal organs in humans, as one possible solution to the ongoing global organ shortage. In the United States alone, nearly 110,000 individuals are on the national transplant waiting list. Kidneys are a particularly urgent target because chronic kidney disease often requires patients to undergo dialysis, a costly and time-consuming treatment that can dramatically disrupt daily life. More than 95,000 individuals in the U.S. are waiting for a kidney transplant, yet in 2025, fewer than 28,000 patients received a human kidney. Around 12 people die each day waiting for a donated kidney. “The organ shortage is the greatest crisis we have right now in transplantation,” Riella says in a statement. “We know that the best treatment option for patients with end-stage kidney disease who have developed renal failure is transplantation, but we simply don’t have enough human organs to transplant in a timely manner.” Doctors say we’re still likely years away from pig kidneys eliminating the need for human kidney transplants. But in the meantime, animal organs could serve as a stopgap for patients waiting for a human one. “Maybe the first more reachable goal is for this treatment to be a bridge, and maybe 10 or 15 years from now, we may be talking about an alternative as good as human kidneys,” Riella tells the Times. “We’re at the beginning of the journey.” You Might Also Like Get the latest stories in your inbox every weekday. More about: Animals Disease Disease and Illnesses Health Medicine New Research Organs