By Zohar Ben Simon, Science & Technology Editor
The FDA recently approved the first clinical trial to test whether pig kidneys can be safely transplanted into living people. In previous years, xenotransplantation, the transplantation of organs from non-human species into humans, has been discussed and even used under extreme circumstances. If this trial proves to be successful, it could change countless lives, and make the transplantations much more accessible, as well as shorten the time that patients are on transplant waiting lists.
Prior to the approval of this trial, only four patients were approved for xenotransplantation. Those who had been granted permission for a transplant using pig organs had no other options, and would have likely passed away before getting the chance to get a human organ transplant. Therefore, the FDA offered a ‘compassionate use’ approval.
In 2022, David Bennett was the first living person to receive a xenotransplant. Since his case was an emergency, the FDA granted authorization for the surgery. He underwent the transplant using a genetically modified pig heart, but he unfortunately passed away about two months after the surgery. The three other patients that had received the pig organ transplant also died shortly after. It is possible that some of these deaths were not solely related to the transplant of a pig organ, but rather due to other underlying medical issues.
About half a dozen people in the U.S. and China have received transplants using organs from pigs, with the longest survival rate post-surgery being 71 days. Pig organs are similar in anatomy and size to those of humans, making them seemingly ideal for transplantation; however, they are still not the perfect, long term solution.
The organs that are used for these transplants come from genetically modified pigs, which aims to lessen the risk of the organs being rejected. One issue that genetic modification targets is to ensure that the organs do not grow after transplantation. The two organizations providing the organs, United Therapeutics and eGenesis, attempt to stop this growth in different ways; United Therapeutics deactivates a certain gene in the pigs to prevent organ growth, while eGenesis uses miniature pig breeds. Another issue is the human body’s rejection of the organ. To prevent this, the antibodies in the patients must be produced to fight against the pig antigens.
This newly approved trial will include six participants, aged 55-70, who are not likely to get a conventional transplant in the next five years, and will most likely die while waiting. Their survival rates will be studied as well as the length of their survival post-transplant. The doctors and scientists will screen and monitor recipients for infections that could possibly be transferred from the pig to the patient. The FDA is enforcing breaks between the patients to assure safety, and after a review of these six patients’ progress, it will be decided whether the trial should expand.
United Therapeutics and eGenesis will both use different sets of genetic modifications; the pigs that United Therapeutics will be utilizing have merely ten genetic changes, while eGenesis’ will have 69 modifications.
The need for an organ source for transplantations is crucial. In the U.S., over 48,000 organ transplants were performed in 2024, however there are still over 103,000 people on the waiting list. The approval of this trial is a pivotal point in medical history, and its success has the possibility of saving countless lives.