Transplanting lungs is a tricky business. Far fewer of them are successfully harvested from organ donors—less than 15%, compared to the 88% viability rate seen with more solid tissues such as kidneys and livers.
The lungs can be vulnerable to several complications during death, such as ventilator-associated injuries, chest trauma and the aspiration of fluids. In addition, a large number of potentially suitable lungs may be rejected for transplantation unnecessarily.
And that’s before the dangerous process of moving them from point A to point B. Speed is essential, but transporting lungs by airplane can expose the tied-off organs to harmful changes in air pressure, causing them to inflate and stretch like a balloon.
To help rescue potentially viable lungs—including those initially deemed unacceptable for transplant—the FDA has approved a device system that flushes and oxygenates the donated organ once it's outside of the body, while washing it in a preservative.
The XPS system and STEEN solution, developed by Xvivo Perfusion and United Therapeutics, are designed to allow marginal-quality lungs to be ventilated and kept at body temperature for up to five hours, giving surgeons the opportunity to reassess their suitability for transplant.
The system includes a disposable, sterile chamber and cart-based hardware that provides in-line gases, humidity, heating and cooling, and is configured to allow the lungs to be X-rayed during the process. The extracellular solution contains human serum albumin to prevent swelling, and dextran 40 to coat and protect the organ walls.
The FDA originally granted Xvivo’s perfusion system a humanitarian device exemption in 2014, limiting the device’s use to 8,000 patients per year. According to HHS, about 2,530 lung transplants were performed last year, the agency said, while Xvivo says at least 400 transplants have been completed using its perfused lungs.
For the full premarket approval, the FDA evaluated a study of 332 sets of donor lungs split into three groups: a control arm of lungs deemed suitable for transplant after standard preservation, plus two groups of lungs initially deemed unsuitable and were either implanted or not following perfusion using the Xvivo system.
After one year, the survival rate for patients with the perfused lungs reached 86.4%, which the agency said was close enough to the control group’s 94% survival rate to not be a clinically significant difference. A post-approval study will follow patients for at least three years.
"We are grateful to the FDA for approving this technology that enables otherwise discarded lungs, which would be unable to be used in furtherance of their donors' generous intent, to instead be frequently restored to transplantable and hence life-saving condition,” Martine Rothblatt, United Therapeutics’ chairman and CEO, said in a statement. “I feel it is a miracle of biotechnology that will benefit thousands of patients who die needlessly awaiting transplant.”