Two patients who received genetically engineered pig kidney transplants have subsequently undergone successful human organ transplants, marking a significant milestone in the development of xenotransplantation, the practice of transplanting animal organs into humans. The patients, among the first to receive pig kidneys developed by biotech company EGenesis, were able to avoid continuous dialysis for several months before human donor organs became available.
Both recipients eventually had the pig kidneys removed and were placed back on dialysis while awaiting human transplants. Despite this, physicians noted that the time off dialysis improved the patients’ overall health and quality of life during the waiting period. The transplant procedure was motivated by the persistent shortage of human kidneys for transplantation, which leads many patients to spend extended periods on dialysis or die waiting for an organ.
David Mulligan, a professor emeritus of surgery at Yale School of Medicine not involved in the research, described the pig kidney transplants as proving the concept that xenografts can provide a functional bridge to human organ transplantation. While the xenografts did not replace the need for human organs in these cases, they allowed patients to avoid dialysis for months at a time, which is considered a meaningful clinical benefit.
Dialysis, the current standard treatment for kidney failure, only replicates a fraction of the kidney’s functions and cannot fully prevent the accumulation of toxins in the body. Prolonged dialysis is linked to various complications, including cardiovascular issues. One recipient, Tim Andrews, had experienced two heart attacks while on dialysis before receiving the pig kidney transplant. According to Mike Curtis, president and CEO of EGenesis, Andrews’ health and mobility significantly improved after implantation, enabling him to regain energy and physical activity. When he returned to dialysis ahead of his human transplant, he was reportedly in better condition than before receiving the xenograft, which may have been crucial in preserving his eligibility for a human organ.
The experience was more challenging for another patient, Bill Stewart, who suffered side effects such as fluid retention and anemia while receiving the pig kidney, along with signs of micro-rejection. His medical team ultimately decided to remove the organ for his safety. Researchers have since refined their immunosuppressive drug protocols based on data from Stewart and Andrews, aiming to reduce complications in future recipients.
The pig kidneys are genetically modified to reduce the risk of rejection and prevent transmission of diseases from pigs to humans. Since March 2024, five patients have received EGenesis pig kidneys under clinical trial conditions. The company’s goal is to eventually provide xenografts that eliminate the need for subsequent human transplants entirely, but the current focus is on safely prolonging dialysis-free intervals.
Curtis emphasized that even temporary relief from dialysis is valuable, noting that human kidney transplants often function as bridges themselves, lasting a limited number of years. The ability to extend time without dialysis may help address the shortage of available donor organs.
Despite these promising early results, experts caution that the technology remains experimental. Mulligan highlighted several open questions, including the cost, production capacity of xenografts, and strategies for safely scaling access to these transplants. Further research is needed to determine whether genetically engineered pig organs can become a sustainable and widely available option for patients with kidney failure.