A 58-year-old patient with terminal heart disease became the second patient in the world to receive a successful transplant of a genetically-modified pig heart on September 20. He is currently breathing on his own, and his heart is functioning well without any assistance from supportive devices. Both surgeries were performed at the University of Maryland Medical Center.

The first surgery, in January 2022, was conducted on David Bennett who died a couple of months later.

The second patient, Lawrence Faucette, had end-stage heart disease. He was deemed ineligible for a traditional transplant due to his pre-existing peripheral vascular disease and complications with internal bleeding. “At least now I have hope and I have a chance,” Mr Faucette said before the surgery. “I will fight tooth and nail for every breath I can take.”

The US Food and Drug Administration granted emergency approval for the surgery on Friday September 15 through its single patient investigational new drug (IND) “compassionate use” pathway. This approval process is used when an experimental medical product, in this case the genetically-modified pig’s heart, is the only option available for a patient faced with a serious or life-threatening medical condition. The approval was granted in the hope of saving the patient’s life.

Transplanting animal organs (xenotransplantation) is potentially life-saving but risky. It could transmit a pathogen from the animal to human or trigger a dangerous immune response..

Three genes—responsible for a rapid antibody-mediated rejection of pig organs by humans—were “knocked out” in the donor pig. Six human genes responsible for immune acceptance of the pig heart were inserted into the genome. One additional gene in the pig was knocked out to prevent excessive growth of the pig heart tissue, for a total of 10 unique gene edits made in the donor pig.

Xenotransplantation from pigs raises a number of bioethical issues. Franklin G. Miller, of Weill Cornell Medical College, recently reviewed the publicity given to this exciting new development. He recommended that bioethicists and journalists scrutinise the procedures more closely.

“Worthy of greater attention are reflection on whether the potential benefits of xenotransplantation are worth the costs, promoting effective measures to prevent chronic diseases that give rise to the need for transplantation, as well as the challenging question of whether the promise of xenotransplantation justifies the harmful treatment of pigs and baboons in pursuit of this innovation.”