In a historic procedure surgeons in the US have, for the first time, transplanted a genetically modified pig heart into a living human. The patient is currently still alive, has not rejected the pig organ and is being carefully monitored at the University of Maryland Medical Center.
The extraordinary achievement is the culmination of decades of work from scientists around the world. Perhaps the most significant recent steps leading up to this landmark moment were advances in gene editing allowing for the development of pig organs that are not rejected by a human immune system.
The genetically modified pig heart used in the transplant was supplied by regenerative medicine company Revivicor and came from a pig that had been engineered with around 10 particular genetic modifications, all focused on reducing the chances of rejection from a human immune system.
The patient receiving the transplant was a 57-year-old man with terminal heart disease named David Bennett. Too unwell to qualify for a regular heart transplant, Bennett was offered the experimental treatment as a last resort.
“It was either die or do this transplant,” Bennett said before the surgery. “I want to live. I know it’s a shot in the dark, but it’s my last choice.”
After much consideration the US Food and Drug Administration (FDA) authorized the surgery as part of a compassionate use provision allowing for experimental treatments in patients with life-threatening conditions.
“This is the culmination of years of highly complicated research to hone this technique in animals with survival times that have reached beyond nine months,” explains Muhammad Mohiuddin, from the Cardiac Xenotransplantation Program at the University of Maryland School of Medicine. “The FDA used our data and data on the experimental pig to authorize the transplant in an end-stage heart disease patient who had no other treatment options. The successful procedure provided valuable information to help the medical community improve this potentially life-saving method in future patients.”
Since the discovery of CRISPR gene editing over a decade ago, researchers have raced to develop genetically modified pigs to create a reservoir of organs suitable for human transplantation. Following several successful preclinical studies transplanting genetically modified pig organs into baboons, two key experiments last year explored human responses to the organs.
The two transplants last year, by researchers from NYU Langone, were performed in functionally dead patients who were kept alive on ventilators for several days. In both instances a genetically modified pig kidney was transplanted into the recently deceased human subjects, who were then monitored for signs of immune rejection for several days.
Bartley Griffith, the surgeon who performed the landmark procedure, is cautiously optimistic about his patient’s prospects. In the three days since the procedure the organ has not been rejected by the patient’s immune system, but it is still early days.
“This was a breakthrough surgery and brings us one step closer to solving the organ shortage crisis,” says Griffith. “There are simply not enough donor human hearts available to meet the long list of potential recipients. We are proceeding cautiously, but we are also optimistic that this first-in-the-world surgery will provide an important new option for patients in the future.”
Obviously Bennett will be closely watched over the coming days and weeks as researchers study the long-term effects of this extraordinary milestone in medical science.
