Revivicor sees 2 months of normal function from a xenotransplanted kidney-plus-thymus

United Therapeutics’ Revivicor division announced that its organ manufacturing platforms, which employ genetically engineered tissues derived from pigs, have shown new promise in human transplants and may set the stage for full clinical trials in the coming years.

The company reported what it described as the longest documented case of a xenotransplanted organ demonstrating normal function within a human body, with a modified kidney designed to treat end-stage renal disease.

Surgeons at NYU Langone Medical Center tracked the activity of United Therapeutics’ UThymoKidney—a manufactured kidney that also contains a portion of the thymus gland taken from the same pig—for 61 days.

While the pig itself had one gene modified to eliminate the production of a specific sugar on the surface of its cells, which can lead to immediate organ rejection in humans, the addition of part of a thymus gland also helps teach the recipient’s immune system to recognize the tissue as a normal part of the body.

The xenokidney was placed within a 58-year-old man who had been on a ventilator after being declared brain-dead, with the procedure being performed with his family’s consent, the company said in its announcement.

At the same time, United Therapeutics disclosed that it completed its second xenoheart transplant through a successful procedure at the University of Maryland Medical Center that received emergency approval from the FDA.

The patient, now recovering, was a living man with end-stage heart failure that was deemed ineligible for a traditional transplant with a donor heart, due to preexisting peripheral vascular disease and complications with internal bleeding. 

The company’s UHeart is derived from pigs with 10 modified genes—including four that had been knocked out, plus the addition of six more taken from human DNA—to help get the organ past the body’s immune system defenses and keep the organ from growing past the point that is normal for humans. United Therapeutics’ separate UKidney is being developed from the same 10-gene modified pig.

“The second transplantation of a UHeart into a living person and the extended study of a UThymoKidney in a decedent, coupled with other ground-breaking research by our collaborators at the University of Alabama at Birmingham, University of Maryland Medicine, and NYU Langone Health, form the basis of knowledge we are sharing with the FDA ahead of commencing future clinical studies of xeno organs in humans,” Leigh Peterson, Ph.D., United Therapeutics’ executive vice president for product development and xenotransplantation, said in a statement. 

“We look forward to continuing our dialogue with the FDA with the goal of starting clinical studies in 2025,” Peterson said. In addition, the company is finalizing construction of a $100 million, pathogen-free facility in Christiansburg, Virginia, to help support the scale needed for clinical xenotransplantation trials—with the goal of producing about 125 organs per year—as it works to complete ongoing preclinical studies.

United Therapeutics’ organ manufacturing efforts include seven programs: xenoheart, xenokidney and xenothymokidney, as well as regenerative lungs and 3D-printed lungs, livers and kidneys.

The company estimates that about 110,000 people in the U.S. are currently on lists for transplants, with over 6,000 dying each year as they wait. Still more patients with organ failure are denied access due to the lists’ strict criteria.

To date, 10 xenotransplantation procedures have been completed using United Therapeutics’ manufactured organs, comprising two living recipients of xenohearts, two brain-dead recipients of xenohearts and six brain-dead recipients of the company’s xenokidneys and thymokidneys.