A U.S. man who received a kidney from a genetically modified pig survived for 271 days and subsequently underwent a successful kidney transplant from a human donor. This represents the first case demonstrating that xenotransplantation can function as a “bridge” for patients awaiting organ transplants. The findings were published in the international medical journal The Lancet.
A team led by Dr. Leonardo V. Riella, associate professor of nephrology at Massachusetts General Hospital (MGH), transplanted a gene-edited pig kidney on January 25, 2025, into Tim Andrews, a man in his 60s suffering from end-stage renal failure caused by type 2 diabetes. Andrews had only a 9% probability of receiving a kidney transplant within five years, and his risk of dying or being removed from the transplant waiting list had reached 40%.
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, perform cooking and vacuuming, 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 removal of the pig kidney, Andrews underwent additional dialysis treatment for approximately three months. Then, on January 13, 2026, the long-awaited kidney transplant from a human donor was performed. The surgery was successful, and no significant adverse effects were observed during the subsequent six-month follow-up period.
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.
“This patient, who voluntarily participated in such a challenging procedure, is a true pioneer,” Riella said, acknowledging that the patient’s trust and courage advanced the science.
69 Gene Edits, Premised on Careful Patient Selection
The kidney used in this transplant came from a Yucatan miniature pig, a small swine breed. The medical team performed a total of 69 gene edits, including the removal of base sequences that could trigger rejection and the insertion of necessary genes, modifying the organ to be compatible with the human body.
Xenotransplantation—transplanting pig organs into humans—has multiple precedents. In kidney cases, two-month survival had been reported, but the 271 days achieved here significantly extends the longest record.
The research team cautioned, however, that these results stem from careful patient selection and intensive specialized care that may not be available elsewhere, and that this is a single case without a control group. They noted that additional clinical trials are needed to verify efficacy and safety.
While organ transplant waiting periods vary by country and region, many patients experience deteriorating health while waiting for a compatible donor organ to become available. If xenotransplantation is practicalized as a “bridge,” it could significantly contribute to improving survival rates for patients on waiting lists. This case represents an important milestone in transplant medicine by concretely demonstrating that feasibility.
