On Nov. 3, 2025, United Therapeutics, a public benefit corporation, announced the first clinical xenotransplantation in its EXPAND study of the UKidney™ in patients with end-stage renal disease (ESRD). The successful transplant operation was performed at NYU Langone Health.

United Therapeutics’ UKidney is an investigational xenokidney from a pig with 10 gene edits. Six human genes are added to the pig genome to facilitate immunological acceptance and compatibility of the organ in the human recipient. Four porcine genes are inactivated or “knocked out” to reduce the risk of organ rejection and to moderate organ growth.

EXPAND is a multicenter, open-label, safety and efficacy study and is intended to support a Biologics License Application (BLA) with the U.S. Food and Drug Administration (FDA). The study is designed as a combination phase 1/2/3 trial (sometimes referred to as a “phaseless” study) to evaluate safety and efficacy seamlessly without moving through separate phase 1, phase 2, and phase 3 studies that are typically associated with conventional drug approvals.

Study participants will receive a UKidney transplant followed by a 24-week post-transplant follow-up period, including the evaluation of all study endpoints and safety assessments. After the 24-week post-transplant follow-up period, participants who received a UKidney will continue to be followed for the rest of their lives, including monitoring for UKidney function and zoonotic infections.

Efficacy endpoints include participant survival rate, UKidney survival rate, change in measured glomerular filtration rate, and change in quality of life in participantsⁱⁱ at 24 weeks post-transplant. Overall survival time of participants receiving a UKidney and overall survival time of the UKidneys themselves are also efficacy endpoints.

Additional key participation criteria include an age of 55 to 70 years old, a diagnosis of ESRD, and at least six months on hemodialysis. Participants will be screened using a crossmatch assay to assess expected immunological compatibility with the UKidney. Participants must not need multiple organ transplants; must not have severe medical co-morbidities, including but not limited to advanced cardiovascular disease, severe peripheral vascular disease, severe neurological disease, chronic pulmonary disease, and uncontrolled diabetes; and must not have a history of medical noncompliance that may preclude adherence to the demands and requirements of xenotransplantation.

According to the American Kidney Fund, there are approximately 815,000 patients with kidney failure in the United States and more than 555,000 patients on dialysis, approximately 90,000 of whom are on the U.S. kidney transplant waiting list. Only 22,000 deceased donor kidney transplants occurred in 2024. A 2021 study found that three years after starting dialysis, only 12% of patients had been placed on an Organ Procurement and Transplant Network kidney transplant waitlist while more than 40% died.