In this photo provided by the United Therapeutics Corporation, a genetically modified pig stands inside the protective barrier at the company's designated pathogen-free facility in Christiansburg, Va., in May 2024. These pigs will eventually supply organs for clinical trials. (United Therapeutics Corporation via AP)
A pig stands in a pen at the Revivicor research farm near Blacksburg, Va., on May 29, 2024, where organs are retrieved for animal-to-human transplant experiments. (AP Photo/Shelby Lum)
David Ayares, president and chief scientific officer of Revivicor, looks at pigs at the company's research farm near Blacksburg, Va., on May 29, 2024, where organs are retrieved for animal-to-human transplant experiments. (AP Photo/Shelby Lum)
Genetically modified piglets gather together at the Revivicor research farm near Blacksburg, Va., on May 29, 2024, where organs are retrieved for animal-to-human transplant experiments. (AP Photo/Shelby Lum)
In this photo provided by the United Therapeutics Corporation, genetically modified pigs stand inside the protective barrier at the company's designated pathogen-free facility in Christiansburg, Va., in May 2024. These pigs will eventually supply organs for clinical trials. (United Therapeutics Corporation via AP)
Seen through a microscope, DNA is removed from a pig egg cell near Blacksburg, Va., on May 30, 2024, before a genetically modified cell is inserted. (AP Photo/Shelby Lum)
A worker at United Therapeutics' designated pathogen-free facility in Christiansburg, Va., on May 29, 2024 retrives a UV sterilized item from behind a protected barrier within the facility. (AP Photo/Shelby Lum)
United Therapeutics' designated pathogen-free facility in Christiansburg, Va., on May 29, 2024. (AP Photo/Shelby Lum)
PIgs stand in pens at the Revivicor research farm near Blacksburg, Va., on May 29, 2024, where organs are retrieved for animal-to-human transplant experiments. (AP Photo/Shelby Lum)