Pig kidney serves as bridge to human transplant in first reported case

A genetically modified pig kidney has functioned inside a living patient for a record nine months, successfully serving as a temporary bridge to a subsequent human donor transplant for the first time.

The 66-year-old patient with end-stage kidney disease had just a nine percent chance of receiving a human kidney within five years, while facing a more than 40 percent risk of dying or being removed from the transplant waiting list. In January 2025, he underwent a pig kidney xenotransplantation. The genome-edited organ kept him dialysis-free for a record nine months before he became the first patient to successfully transition to a human kidney transplant. His case has been detailed by researchers at Massachusetts General Hospital and Harvard Medical School in The Lancet.

'We know that the best treatment option for patients with end-stage kidney disease who have developed renal failure is transplantation, but we simply don't have enough human organs to transplant in a timely manner,' said lead author Dr Leonardo Riella, associate professor of medicine and surgery at Harvard Medical School and medical director for kidney transplantation at Mass General Brigham. 'Our vision is that xenotransplantation could help address this gap – initially as a bridge to get patients off dialysis while they wait for a human donor kidney, and potentially, as we establish long-term safety and durability, as a destination therapy in its own right.'

The porcine organ came from a Yucatan miniature pig engineered by biotech company eGenesis, which is based in Cambridge, Massachusetts. Using CRISPR/Cas9, researchers introduced 69 genetic modifications into the donor pig: inactivating pig viruses to reduce the risk of infection, switching off pig genes that would trigger immune rejection in humans, and inserting human genes to regulate inflammation and blood clotting as well as improve compatibility.

The research team from eGenesis had previously used a similar genome editing approach to produce genetically modified pigs for xenotransplantation. In 2024, the world's first xenotransplant of a genetically engineered pig kidney into a living human recipient was performed at Massachusetts General Hospital. The patient survived for 52 days before dying from cardiac causes unrelated to the transplant (see BioNews 1232). The same approach has also been used to engineer pig livers, which successfully filtered blood for three days when temporarily connected to a brain-dead human recipient (see BioNews 1223).

After the surgery, the xenograft kidney immediately began functioning and allowed the patient to maintain dialysis independence for 271 days. However, the organ developed microvascular injury and inflammation after about six months; this ultimately led to graft failure and removal of the kidney at nine months post engraftment. After 82 days back on dialysis, the patient received a human donor kidney that functioned immediately with no evidence of immune sensitisation during six months of follow-up.

The case represents the longest reported period of effective pig kidney function in a living patient and demonstrates the potential of xenotransplantation as a temporary bridge to human transplantation. However, the authors emphasised that this outcome represents a single carefully monitored patient under experimental 'compassionate use' protocol, rather than evidence that animal organs can immediately replace human donations. Further clinical trials are necessary to establish the safety, durability, and wider applicability of this approach.