A 54-year-old New Hampshire man has become the latest success story in experimental pig kidney transplantation, achieving a dialysis-free life following his June 14 procedure at Massachusetts General Hospital. Bill Stewart's successful transplant, announced Monday by biotech company eGenesis, represents a crucial milestone as the field moves toward formal clinical trials.
Stewart, an athletic trainer from Dover, New Hampshire, received a genetically engineered pig kidney known as EGEN-2784 and was discharged from the hospital just one week later. He had been receiving dialysis three times a week for more than two years before the transplant, after high blood pressure caused his kidneys to fail.
"I really wanted to contribute to the science of it," Stewart told The Associated Press, describing himself as "a little bit of a science nerd." He noted that patients with his blood type can wait up to seven years for a matching kidney from a deceased donor.
Record-Breaking Transplant Success
Stewart's procedure follows another breakthrough case from the same eGenesis study. Tim Andrews, 67, of Concord, New Hampshire, received his pig kidney transplant on January 25, 2025, and continues to live dialysis-free seven months post-transplant. This duration represents a new record for gene-edited pig organ transplants, surpassing the previous longest-known survival of 130 days.
According to eGenesis, Stewart and Andrews are the second and third people worldwide to receive an EGEN-2784 kidney. Both patients have required adjustments to their anti-rejection medications, according to Dr. Leonardo Riella, a kidney specialist at Mass General who will help lead upcoming clinical trials.
FDA Approval Launches Clinical Trial Era
In conjunction with announcing Stewart's successful transplant, eGenesis revealed that the U.S. Food and Drug Administration has cleared its investigational new drug application to begin a clinical trial evaluating EGEN-2784 kidneys for patients with end-stage kidney disease.
The approved trial will provide gene-edited pig kidney transplants to 30 people age 50 or older who are on dialysis and the transplant waiting list. This represents a significant shift from previous one-off experimental procedures to rigorous clinical studies designed to establish safety and efficacy.
"Right now we have a bottleneck" in finding enough human organs, said Dr. Riella, highlighting the critical need for alternative solutions.
Addressing the Organ Shortage Crisis
More than 100,000 people are currently on the U.S. transplant list, with the majority needing kidneys, and thousands die while waiting for organs. Scientists are genetically altering pigs to make their organs more humanlike and less likely to be immediately attacked and destroyed by the human immune system.
Previous experimental attempts have shown mixed results. Initial experiments involving two hearts and two kidneys were short-lived and included very ill patients. An Alabama woman whose pig kidney lasted 130 days before rejection helped researchers shift their approach to focus on healthier patients rather than those who were critically ill.
Patient Experience and Recovery
Stewart's recovery has been notably positive. Thrilled to no longer have his time and energy depleted by dialysis, he is easing back into desk duties at work and has visited his former dialysis clinic to "let everyone know I'm doing all right and maybe kind of give some people some hope."
Before his procedure, Stewart sought advice from Andrews and ultimately decided that "worst case scenario, they can always take it out." His decision was influenced by the lengthy wait time for a compatible human donor and the fact that potential living donors didn't qualify.
Future Prospects
Dr. Riella emphasized that while it's too early to predict how long pig kidneys might last, even temporary success could provide significant benefits. "A year, hopefully longer than that – that's already a huge advantage," he said, noting that pig kidneys could buy patients valuable time off dialysis until they receive a matching human organ.
The field is expanding rapidly, with United Therapeutics, another developer of gene-edited pig organs, preparing to start enrolling participants in a similar FDA-approved study. These parallel efforts represent the most comprehensive approach to xenotransplantation research to date, potentially offering hope to thousands of patients facing lengthy waits for life-saving organ transplants.
