A U.S. man who received a genetically modified pig kidney survived for 271 days and subsequently underwent a successful kidney transplant from a human donor.
Fortunately, a kidney from a deceased donor became available, and the pig kidney was removed 271 days after transplantation, in October 2025.
Successful Human Kidney Transplant, No Antibody ResponseAfter the pig kidney was removed, Andrews underwent approximately three months of additional dialysis treatment.
This indicates that the pig kidney transplant did not impede the subsequent human kidney transplant.
The company refers to the transplanted pig kidney as "EGEN-2784."
A U.S. man who received a genetically modified pig kidney survived for 271 days and subsequently underwent a successful kidney transplant from a human donor. This represents the first case demonstrating that xenotransplantation can serve as a "bridge" for patients awaiting transplants. The findings were published in the international medical journal The Lancet.
A team led by Leonardo V. Riella, associate professor of nephrology at Massachusetts General Hospital (MGH), transplanted a gene-edited pig kidney into Tim Andrews, a man in his 60s suffering from end-stage renal failure caused by type 2 diabetes, on January 25, 2025. Andrews had only a 9% probability of receiving a kidney transplant within five years, with a 40% risk of dying or being removed from the transplant waiting list.
A biopsy performed 14 days after the transplant confirmed T cell-mediated rejection, which was resolved through treatment. The pig kidney then functioned stably for six months. Andrews was able to walk without dialysis, cook, and vacuum, and by June 2025 had recovered sufficiently to throw out the ceremonial first pitch at a baseball game.
However, inflammation subsequently appeared in the kidney's microvasculature, progressing to thrombotic microangiopathy. Fortunately, a kidney from a deceased donor became available, and the pig kidney was removed 271 days after transplantation, in October 2025.
Successful Human Kidney Transplant, No Antibody Response
After the pig kidney was removed, Andrews underwent approximately three months of additional dialysis treatment. Then, on January 13, 2026, the long-awaited human donor kidney transplant surgery was performed. The surgery was successful, and no significant adverse effects have been observed during the subsequent six months of follow-up.
According to the research team, no new antibodies against human tissue were detected in Andrews' body. Additionally, no pig-derived viruses or pathogens were detected. This indicates that the pig kidney transplant did not impede the subsequent human kidney transplant.
Riella stated, "The patient who voluntarily participated in such a challenging procedure is a true pioneer," expressing the view that patient trust and courage advanced the science.
69 Gene Edits, Premised on Careful Selection
The kidney used in this transplant came from a Yucatan miniature pig, a small pig breed. The medical team performed a total of 69 gene edits, including removal of base sequences that could trigger rejection and insertion of necessary genes, modifying the organ to be compatible with the human body.
These 69 edits fall into three broad categories: removal of three pig antigen genes that cause hyperacute rejection, insertion of seven human genes to enhance immune system compatibility, and inactivation of 59 copies of porcine endogenous retrovirus (PERV), which theoretically pose a risk of human infection (3+7+59=69). The design was developed by eGenesis, a company founded by Harvard University professor George Church, a leading figure in gene editing research. The company refers to the transplanted pig kidney as "EGEN-2784."
