The first clinical trial of transplanting genetically modified pig livers into patients with liver failure has received approval from the U.S. Food and Drug Administration (FDA), international journal Nature reported on the 15th (local time). U.S. and U.K. biotechnology companies eGenesis and OrganOx are participating in the clinical trial.
Liver failure is a disease in which liver function decreases and cannot detoxify blood waste. Wayne Hawson, a professor of transplant surgery at the University of Sydney, former president of the International Xenotransplantation Association, noted to Nature, "This clinical trial will bring significant progress in treating liver failure, which has a mortality rate of 50%."
While many patients are waiting for organ transplants, the number of donors is low. According to the National Organ and Tissue Blood Management Center in South Korea, there are about 51,800 patients waiting for organ transplants in 2023. The number of organ donors is insufficient at around 400.
As a result, the method of transplanting pig organs, which have a structure similar to that of humans, is emerging as an alternative. However, our bodies recognize pig organs as invaders and attack them, so attempts are being made to genetically modify pig livers to resemble those of humans.
In this clinical trial, four patients will receive pig livers, with ages ranging from the 10s to the 70s. Included are patients whose liver failure has worsened from chronic to acute or who have developed hepatic encephalopathy due to liver dysfunction.
The clinical trial will involve transplanting pig livers into patients for 72 hours to verify whether they function properly and eliminate blood waste. After that, they will be monitored for safety issues for one year. If regulatory authorities deem it safe, a decision will be made on whether to increase the number of clinical trial participants to 20.
Professor Wayne Hawson said, "The pig liver will serve as a bridge to save people suffering from liver failure." It means patients can buy time with pig livers until they can find a liver for transplantation.
There have been previous cases of transplanting pig livers into humans. Chinese scientists reported last month in "Nature" that genetically modified pig livers functioned normally for 10 days after being transplanted into deceased donors.
The pig liver began secreting bile two hours after transplantation. It was confirmed that albumin, a protein synthesized by the liver, was also secreted normally. The experiment ended after 10 days at the request of the deceased donor's family. The fact that clinical trials are being conducted on actual liver failure patients is thanks to the confirmation of success potential in earlier tests.
eGenesis received FDA approval last year to transplant genetically modified pig kidneys into patients with kidney failure. This patient was discharged from the hospital in February this year and has also stopped dialysis. The company transplanted genetically modified pig kidneys into a second patient in January of this year.
Pig hearts have also been transplanted into patients. In October 2023, a patient with heart failure received a pig heart in the U.S. and died six weeks later. At that time, the patient was undergoing rehabilitation without any significant rejection reactions before passing away.
References
Nature(2025), DOI: https://www.nature.com/articles/d41586-025-01209-6
Nature(2025), DOI: https://doi.org/10.1038/s41586-025-08799-1