First Genetically Modified Pig Heart Transplanted to a Human


David Bennett Sr., a 57-year-old Maryland man, received a transplant of a genetically modified pig heart. The first-of-its-kind transplant surgery was performed earlier this year on January 10, by surgeons at the University of Maryland Medical Center, Baltimore. Dr. Bartley Griffith, the director of the cardiac transplant program at the medical center, led the operation.

It was a high-risk experimental procedure, but as Mr. Bennett had terminal heart disease and was “medically non-compliant,” he was deemed ineligible for a conventional heart transplant or an artificial heart pump. Due to these complications, his surgeon, Dr. Griffith, suggested the pig heart. The first xenotransplantation, the process of grafting or transplanting organs or tissues from animals to humans, has been accomplished without its immediate rejection by the body.

Pigs are usually preferred as hosts for growing donor organs due to their short growth period. For years, pigskin has been used as grafts for burn victims and pig heart valves have also been transplanted into humans. The transplanted heart was provided by Revivicor, a regenerative medicine company based in Blacksburg, VA. The heart was grown in a pig with genetic modifications specifically made to complement Mr. Bennett’s body. It took almost six months for the pig to grow the human-sized heart and all efforts were taken to reduce the likelihood of organ rejection by his immune system, a fairly common problem in organ transplants.

Newer technologies like gene editing and cloning have allowed genetically altered animal organs to be less likely to be rejected by humans. Scientists modified ten genes in the pig, ensuring that the heart matches a human heart. Three genes that encoded for known antibody responses, causing the new heart to be rejected immediately, were turned off.  The growth gene was also inactivated, preventing the pig’s heart from continuing to grow in Mr. Bennett’s body. Furthermore, six human genes were inserted into the donor pig’s DNA, to make Mr. Bennett’s immune system accept the porcine organ more readily. 

The team used a new experimental drug developed by Dr. Muhammad Mohiuddin, a professor of surgery at the University of Maryland School of Medicine, and made by Kiniksa Pharmaceuticals to suppress the immune system and prevent rejection. A new machine perfusion device was used to keep the pig’s heart preserved until surgery. Finally, on New Year’s Eve, the US Food and Drug Administration worked relentlessly, granting emergency authorization for the surgery.

According to the Health Resources and Services Administration, over 106,000 people in the United States are on the organ donation waiting list — waiting for the death of a registered organ donor who has a compatible kidney, lung, liver, or heart. At the same time, 17 people on average die every day in the US while waiting for organs. There is an obvious shortage of organs in the United States and certainly a need for more organs, so scientists are constantly researching for other methods to meet demand. 

Though it’s too early to declare this transplantation as a complete success, this groundbreaking procedure offers hope to the hundreds of thousands of patients with failing organs. The surgery was the first of its kind, and it is still up to the Federal Drug Administration to approve this type of xenotransplantation for large-scale use. With a terrible shortage of organs for transplants, researchers strongly believe that engineered animal parts can be a solution in the future.


Daniel, Hannah. “First Genetically-Altered Pig Heart Transplanted to a Human: Health and Medicine.” Labroots, Labroots, 15 Jan. 2022,