There are more than 100,000 people currently waiting for an organ transplant and it’s estimated that another person is added to the waitlist every 8 minutes, according to the Health Resources & Services Administration. There aren’t enough organs to go around and 17 people die each day waiting for one, HRSA estimates.
Dr. Robert Montgomery, director of the NYU Langone Transplant Institute, understands this problem better than most. He's not just a transplant surgeon, he's also an organ recipient, having received a donor heart.
"Even though I had seven cardiac arrests and could have died in any of those events, I still was not sick enough to really draw an organ," he told ABC News. "And that's really when it became so clear to me that we had to find another source of organs other than human organs."
A possible answer: genetically modified animal organs. In 2022, Maryland man David Bennett Sr. lived 60 days as the first person to receive a pig heart -- his severe congestive heart failure meant he wasn't a candidate for a human transplant.
Bennett and three others received gene-edited pig organs through the FDA's compassionate use program, which allows xenotransplants under special and highly vetted circumstances. All four of these people died within three months of their surgeries, but this experimental procedure continues to develop.
ABC News became the first television crew invited to a Blacksburg, Virginia, research farm that raises pigs. The pigs born on this farm are genetically modified to delete certain pig genes and add human genes, so it’s less likely the recipient's body will reject the organ.
Dr. David Ayares is the president and chief scientific officer of Revivicor, the United Therapeutics-owned company that raised the gene-edited pigs used for Bennett's and others' transplants. Ayares has made perfecting these transplants his life's work.
"If you were to put an unmodified farm pig organ, whether it's a kidney or a heart, into us, we would reject it in a matter of minutes," he told ABC News. "So we're actually adding a gene that inhibits the immune system right to the organ. And so ultimately now we've knocked out or deleted four pig genes and added six human genes."
Many of the farm's cloned pig eggs are eventually used to grow into genetically modified pigs, and they live in a highly secured lab.
ABC News wasn't allowed to see those pigs due to the stringent pathogen-free requirements. However, video provided by Revivicor shows what they say are the pigs in their air-conditioned pens, manned and cleaned around the clock by trained employees and veterinarians.
There still hasn’t been wide-scale approval of xenotransplantation by the FDA -- approval is on a case-by-case basis. The next milestone in this new medical frontier is for the agency to approve human clinical trials. If that goes well, they could allow xenotransplantation on a much wider scale.
The science is still very much in the early stages and experts like bioethicist Dr. Insoo Hyun told ABC News that more research is needed.
"The science and the biology of xenotransplantation makes us such that these organs are not quite as good as human organs," he said. "This has set up kind of, like a two-tier system of quality and outcomes for patients -- that's a real concern. But again, that's to be determined by what the science shows."
Ayares cautioned that xenotransplantation is "not the silver bullet... not the single thing that's going to solve" the organ shortage, but believes the science around transplants will advance greatly in the next decade.
"I think 10 years from now, it's going to be a completely different paradigm," he told ABC News. "We'll be able to custom design the organs for, you know, these advanced diseases as we learn about them."
Towana Looney became the latest person to receive a genetically modified pig organ -- a kidney -- in November. Years after donating one of her kidneys to her mother, Looney developed kidney disease and found herself in need of a transplant.
She is currently the healthiest person to receive a pig organ yet. She had been on the transplant list waiting for a human kidney, but her blood was so full of antibodies that she says her body would have rejected more than 300 of them.
Looney's pig kidney arrived by helicopter from United Therapeutics, and the six-hour surgery was performed by Dr. Robert Montgomery of NYU Langone. She felt incredible after waking up with her new kidney, she told ABC News.
"My God. The energy, the blood flow," she said. "I could feel the blood flow through my veins, just how strong the kidney was for me."
For the first time in eight years, Looney is free from the endless cycle of dialysis to treat her kidney disease, her blood pressure is back to normal and she’s embracing the freedom to live, travel and thrive without limits.
"It's just like getting a second chance in life," she said.