Pig Kidneys Successfully Transplanted Into Humans

Organ transplants derived from animals for human use are establishing a track record of clinical success after decades of unfulfilled promise, offering strong prospects for the future of transplantation medicine.

According to US biotechnology firm eGenesis, five patients at Massachusetts General Hospital have undergone successful xenotransplantations—the transfer of animal organs into human recipients—since March 2024 using pig kidneys genetically engineered to prevent rejection. In three of these cases, the porcine organs functioned effectively for more than eight months without rejection or requiring dialysis treatment.

The animal organs would initially be used “as a bridge to get patients off dialysis while they wait for a human donor kidney,” said Riella, adding that it could eventually be used “as a destination therapy in its own right” if the trials “establish long-term safety and durability”.

The kidneys were harvested from Yucatan miniature pigs due to the similar anatomical size of their organs to human kidneys. The animals underwent genetic modification to deactivate three porcine proteins responsible for triggering immune rejection and to incorporate seven human genes aimed at enhancing organ compatibility. Furthermore, the porcine genome was engineered to neutralize endogenous retroviruses that pose an infection risk to human recipients.

As detailed in a recent publication in The Lancet, one patient, Tim Andrews, received a pig kidney at age 66 and maintained functionality without requiring dialysis for nearly nine months. Although the transplanted organ eventually experienced failure, no indications of immune rejection were detected. Mr. Andrews subsequently received a deceased-donor human kidney transplant, with clinical assessments confirming that the prior porcine transplant did not impair the viability or integration of the subsequent human organ.

Curtis stated that the US Food and Drug Administration (FDA) has authorized an expanded clinical trial of eGenesis pig kidneys involving 33 patients with renal failure. Set to initiate early next year across up to 10 US transplant centers, the trial aims to secure commercial marketing approval by late 2029. 

Additionally, eGenesis is partnering with Japanese firm PorMedTec to launch kidney xenotransplantation trials in Japan in 2028.

David Crosby, chief research officer at Kidney Research UK, characterized the advancement as "an exciting prospect." However, he emphasized the necessity of further research to establish whether xenotransplantation offers a safer, superior alternative for patients relative to long-term dialysis while awaiting human donor organs.

While xenotransplantation research has historically experienced alternating periods of optimism and setbacks since the 1980s, concurrent advances in animal cloning, genomic editing, and immunology are now driving significant clinical progress.

Furthermore, public reluctance and ethical opposition regarding the cultivation of animals for organ procurement have substantially decreased. Curtis noted that ethical objections become increasingly difficult to defend when weighed against positive patient outcomes.

Although historical research overwhelmingly prioritized cardiac transplants, renal applications are currently leading the pathway toward regulatory approval. A key clinical advantage of kidney transplants is the availability of dialysis as a therapeutic safety net should organ failure occur, whereas cardiac graft failure presents immediate, life-threatening complications.

Nevertheless, both eGenesis and United Therapeutics continue to advance cardiac applications alongside renal programs, with the FDA recently approving a small-scale clinical trial for xenogeneic heart transplants led by United Therapeutics.