First pig liver transplanted into a living patient: survives 171 days

"This study represents a milestone in hepatology," wrote Heiner Wedemeyer, co-editor of the Journal of Hepatology and of the Department of Gastroenterology and Hepatology at the Medical Faculty of Hanover, in an editorial, "It demonstrates that a genetically modified porcine liver can graft and provide key liver functions in a human recipient. At the same time, it highlights the biological and ethical challenges that remain before such approaches can be translated into wider clinical use. Xenotransplantation could open up completely new avenues for patients with liver failure and carcinoma. A new era for transplant hepatology has begun.

Until now, pig livers had only been used on brain-dead patients to test biological feasibility. In 2023, a genetically modified pig liver was implanted in a 50-year-old brain-dead patient in China for the first time, demonstrating that the organ could be perfused and maintained for several days.

The following year, the US Food and drug administration (Fda) approved a safety clinical trial to connect patients with severe liver failure to an extracorporeal pig liver, which filters blood as a temporary 'bridge' pending recovery or a human transplant.

The next step - today's Chinese one - marked the most ambitious leap: the use of animal liver in a living, conscious patient, paving the way for direct clinical application of xenotransplantation.

According to the World Health Organisation, thousands of people die each year while waiting for an organ transplant due to the shortage of human donors. In the United States alone, over 100,000 patients are on the waiting list for a transplant, over 8,000 in Italy.

Genetically modified pig organs, very similar to human organs in size and physiology, represent a potential answer to the donation crisis. However, the risks of immune rejection and zoonotic infections remain the main challenges to overcome.

The liver case comes amid rapid progress in interspecies research. In March 2024, surgeons at Massachusetts General Hospital in Boston successfully performed the first pig kidney transplant on a living patient, a 62-year-old man with terminal kidney failure: the organ functioned for weeks, confirming the clinical feasibility of the approach.

Shortly afterwards, in New York, 53-year-old Towana Looney became the longest surviving person with a pig kidney, 130 days, before organ rejection. United Therapeutics, which developed the kidney with ten genetic modifications, received the go-ahead from the FDA for a clinical trial on six patients with terminal kidney failure, which is expected to start by the end of 2025.

Also on the heart front, two transplants on live patients were performed in the US between 2022 and 2023, with survivals of up to two months.

And in 2025, the first pig lung transplant in a brain-dead patient was documented in China, confirming that anatomical and physiological compatibility can also extend to other vital organs.

For researchers, the 2025 data mark a point of no return: xenotransplantation has moved from theory to the experimental clinic, and could change transplantation medicine forever.