Man Has Pig Kidney Removed After Living With It for a Record 9 Months

Surgeons at Massachusetts General Hospital have removed a genetically engineered pig kidney from a 67-year-old New Hampshire man after a period of decreasing kidney function, the hospital confirmed to WIRED in a statement. The organ functioned for nearly nine months, longer than previous pig organ transplants, before it was removed on October 23.

Tim Andrews received the pig kidney on January 25 after being on dialysis for more than two years due to end-stage kidney disease. His rare blood type meant that he faced a much longer wait time for a human donor kidney than most patients, who already wait on average three to five years for a kidney.

The shortage of human donors has pushed scientists to look to animals as a potential source of organs. Kidneys are the most in demand, with nearly 90,000 people waiting to receive one in the US alone. Due to the shortage of organs, the US performed just 28,000 kidney transplants in 2024.

Pig organs are being explored as an option, though genetic differences between pigs and humans mean they would be swiftly rejected if they were transplanted into a person. Scientists have therefore turned to gene editing to make pig organs more compatible with the human body, and have so far carried out a handful of experimental transplants.

Andrews was the fourth person in the world to receive a kidney from a genetically engineered donor pig. The first, Richard Slayman, whose surgery was also performed at Massachusetts General, died in May 2024 almost two months after his transplant. A second person, Lisa Pisano, had a combined pig kidney transplant and heart pump surgery at NYU Langone Health, but had the kidney removed in May 2024 after less than two months due to failure. Pisano later passed away. Towana Looney became the third pig kidney recipient, again at NYU Langone, and lived with the organ for more than four months before surgeons removed it in April this year due to organ rejection.

Since Andrews’ surgery, a patient in China has received an edited pig kidney, and surgeons at Massachusetts General have transplanted one into another patient, 54-year-old Bill Stewart, bringing the total number of people known to have received pig kidneys to six.

Before the pig kidney transplants, two patients received genetically engineered pig hearts at the University of Maryland in 2022 and 2023 but never became healthy enough to leave the hospital. They both died within two months of their procedures.

Andrews was discharged on February 1, and his pig kidney functioned as expected for several months. In July, Leonardo Riella, medical director for kidney transplantation at Mass General, told WIRED that Andrews’ kidney was doing well after showing signs of cellular rejection two weeks following the transplant. Riella and his team were able to successfully treat that rejection to keep his kidney functioning.

Riella said Andrews was on four immunosuppressant medicines to prevent further rejection, which can happen at any point after a transplant. “Off and on, we have had to adjust his medications. It’s definitely more intense than a regular human transplant,” Riella told WIRED at the time.

Andrews’ kidney was provided by biotech company eGenesis in Cambridge, Massachusetts, from a pig donor that was genetically edited using Crispr technology to remove harmful pig genes and add certain human genes. In all, the eGenesis pigs have 69 edits.

For Pisano’s procedure, the NYU team used a donor pig from Revivicor, a subsidiary of Maryland-based United Therapeutics, with a single genetic edit. The donor pig used for Looney’s procedure was also from Revivicor but had 10 gene edits. The number of edits needed to keep pig organs functioning in the human body is something that scientists are actively debating.

Andrews will now resume dialysis and remain on the list for a human donor kidney, according to Mass General.

Though the kidney ultimately failed, eGenesis considers the transplant a success. “The life-supporting function provided by the donor organ highlights the possibilities for patients around the world who are desperately waiting for a transplant,” the company said in a statement provided to WIRED. “Cross-species transplantation has been a goal for centuries that has only recently become possible due to decades of research and the convergence of enabling technologies.”

The hospital plans to carry out another genetically edited pig kidney transplant before the end of the year.