A 66-year-old man survived nearly nine months on a genetically modified pig kidney before finally receiving a human transplant, according to a paper published Thursday in the Lancet, offering fresh evidence that xenotransplantation could become a real option for the tens of thousands of Americans stuck on dialysis and waiting lists.
Tim Andrews had lost his kidneys to diabetes and high blood pressure. He’d survived two heart attacks, had no appetite, and couldn’t walk without struggling. “I was dying,” he said. His rare blood type made a matching human kidney even harder to find. He was one of roughly 90,000 people on the U.S. kidney transplant waiting list, a list where an average of 11 people die every day, according to the United Network for Organ Sharing.
Instead of waiting, Andrews enrolled in an experimental program at Mass General Brigham in Massachusetts. “I figured, if I’m going to die, I might as well do something for humanity and be part of this experiment,” he said. In January 2025, surgeons gave him a kidney from a pig that had undergone extensive genetic editing, including changes meant to prevent severe organ rejection and to inactivate viruses carried in the pig genome.
The kidney worked. “It gave me life,” Andrews said. But over the following nine months he was hospitalized multiple times, and blood clots eventually formed in the organ’s vessels and destroyed it. Doctors removed the pig kidney and Andrews briefly went back on dialysis. In January, he received a matching human kidney donor. These days he spends much of his time at a cabin by a pond, swimming, kayaking, and taking short bike rides.
A Bridge, Not Just an Experiment
Dr. Leonardo V. Riella, the Lancet paper’s lead author and associate director of the Legorreta Center for Clinical Transplant Tolerance at Mass General Brigham, said the pig kidney functioned as a bridge that spared Andrews the worst wear of continued dialysis.
“Dialysis causes so much wear and tear on our patients that they become too sick to get a transplant, or die while waiting,” Riella said.
“The message from patients, and it was very shocking for us, is that life on dialysis is no life. So they’re all looking for that alternative, which is why so many patients have volunteered and stepped forward, even with all the unknowns of research.”
Mike Curtis, president and CEO of eGenesis, the biotech company that engineered the pig and helped fund the study, said Andrews’s case, along with one other patient, showed that having a pig kidney first doesn’t seem to hurt a patient’s chances with a later human transplant.
“It doesn’t seem to change how you react to human tissue at all,” Curtis said. “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.”
Five patients at Mass General Brigham have received eGenesis pig kidneys through an FDA expanded access program reserved for people with no other treatment options. Three of them, including Andrews, lived with their pig kidneys for more than eight months, according to a statement eGenesis issued Thursday. One patient died of an unexpected cardiac event shortly after transplantation, and another was transplanted only in June. eGenesis plans to launch a formal clinical trial with 33 patients next year.
A Field Moving Fast
The pace of progress has been striking. In March 2024, surgeons at Mass General performed the first kidney transplant from a gene-edited pig into a human patient, Rick Slayman, 62, who was discharged two weeks later. Slayman, who had a chronic heart condition, died within two months of an apparently unrelated cardiac event. Before that, the first genetically modified pig hearts were transplanted into human patients in 2022; those recipients had advanced disease and died shortly afterward.
Dr. Muhammad Mohiuddin, a professor of surgery at the University of Maryland School of Medicine and a pioneer of xenotransplantation research, spent decades transplanting pig hearts into baboons before taking part in that first human pig heart transplant.
“I never imagined in my lifetime that I would see the human translation of this,” Mohiuddin said. “The initial progress with nonhuman primates in the lab was slow.”
For patients staring down a shrinking supply of donor organs and a waiting list where death is a daily occurrence, the results out of Massachusetts suggest that animal organs may soon offer a real, if imperfect, way out.
