The Food and Drug Administration has given two biotechnology companies approval for clinical trials that will transplant organs from genetically modified pigs into patients with kidney failure, an experimental but potentially groundbreaking innovation for thousands of Americans on the waiting list for organ transplants.
United Therapeutics Corp. said Tuesday that its trial will start with six patients with end-stage renal disease around the middle of this year. The trial could expand to 50 people who are unable to receive a donor kidney for medical reasons, or who are on the wait-list but are unlikely to receive one within five years.
Another company, eGenesis, said Tuesday it received FDA approval in December for a kidney transplant study on three patients, with the option to expand.
"We are entering a transformative era in organ transplantation," eGenesis chief executive Mike Curtis said Tuesday in an email.
There are more than 106,000 people on the national list for organ transplants in the United States, most of them seeking kidneys. Only about 27,000 kidney transplants were performed in 2023. More than 557,000 patients are on dialysis.
Advances in the field of xenotransplantation - transplanting an organ from one species to another - have been gathering pace, as scientists develop gene-editing techniques that make organs less prone to rejection.
Until now, such transplants have been approved under the FDA's compassionate-use program, which allows the use of investigational medical products outside of clinical trials only when patients are critically ill and running out of options.
Some medical experts have raised ethical and health concerns around such transplants, including the risk of infection from animal-specific diseases that spread among humans and how to help patients effectively weigh the unknown risks.
Participants in the United Therapeutics trial must be between 55 and 70 years old and have been on dialysis for at least six months. Patients will be monitored for at least 12 weeks after surgery and an independent review undertaken before a decision is made on expanding the study.
The idea of using pig organs in humans is not new - one of the first recorded instances was in 1838, when a doctor transplanted a pig cornea into a human in an unsuccessful attempt to fix their eyesight. Pigs are more widely available than some primates, and their organs are more similar to humans, according to medical experts.
An Alabama woman last month became the longest-living recipient of a pig organ transplant. Towana Looney, 53, in November received a pig's kidney with 10 gene edits designed to reduce the risk of organ rejection.
The first recipient, Richard Slayman, a 62-year-old worker for the Massachusetts Department of Transportation, lived for 52 days after the procedure last year. Lisa Pisano, a 54-year-old grandmother, received a pig's kidney and a heart pump on different days in April last year. She survived 86 days, though the gradually failing kidney had to be removed after 47 days.
Looney donated a kidney to her mother decades ago and then developed kidney failure after a complication during pregnancy. She had been on kidney dialysis for nearly eight years, during which she developed very high levels of antibodies abnormally primed to attack another human kidney, making it unlikely that she would ever receive a donated organ.
The pig used in Looney's transplant, developed by a subsidiary of United Therapeutics, had changes to its genetic code including the removal of three immunogenic antigens, molecules that can trigger an immune response.
"Our goal is to increase the availability of transplantable organs to offer a therapeutic alternative to a lifetime on dialysis," Leigh Peterson, executive vice president of product development at United Therapeutics, said in a statement Tuesday.