A 66-year-old man with end-stage renal disease lived for a record nine months with a genetically modified pig kidney, marking a significant milestone in xenotransplantation research. The case, detailed in a new medical report published in The Lancet, demonstrates how animal organs can successfully serve as a temporary bridge for patients facing severe shortages of human donor organs.
The patient, Tim Andrews from New Hampshire, had been undergoing haemodialysis for two years due to kidney failure caused by type 2 diabetes. Faced with an estimated five-year wait for a deceased-donor transplant and a low statistical probability of receiving a human kidney in time, Andrews opted to participate in an experimental xenotransplantation programme at Mass General Brigham in Boston.
Genomic Modifications and Surgery
The kidney transplanted into Andrews on January 25, 2025, originated from a Yucatan miniature pig named Wilma. Researchers at the biotech company eGenesis and Mass General Brigham engineered the organ with 69 specific genomic modifications designed to minimize immune system rejection and remove potential porcine viruses that could infect humans.
Surgeons led by Dr. Leonardo Riella successfully performed the procedure, allowing the patient to come off dialysis immediately as the porcine organ began functioning. According to clinical data, the genetic edits successfully mitigated hyperacute rejection, allowing the animal kidney to sustain normal biological filtration for months without triggering immediate antibodies against human tissue.
Sustaining Daily Life Without Dialysis
The successful integration of the porcine organ provided Andrews with substantial relief from the heavy physical toll of regular haemodialysis treatments. During the months following the operation, he reported being able to perform everyday household tasks, vacuum, cook, and take long walks with his dog.
“I was alive, and I hadn’t been in a long time,” Andrews said of the procedure, describing the outcome as a medical miracle. Medical staff noted that the nine-month duration more than quadrupled previous records for pig organ survival in living human recipients, surpassing earlier trials that typically encountered fatal complications within weeks.
Complications and Organ Failure
Despite the initial success, the porcine kidney eventually began to fail after roughly six months due to progressive damage in the organ's blood vessels. The clinical team noted that Andrews had been hospitalized with a severe methicillin-resistant Staphylococcus aureus infection, commonly known as MRSA.
To manage the infection, doctors reduced the dosage of immunosuppressive drugs administered to prevent organ rejection. This reduction subsequently triggered vascular damage within the xenograft, leading to gradual organ failure and necessitating the removal of the pig kidney 271 days after the initial transplantation procedure.
Transition to a Human Donor Kidney
Following the removal of the porcine kidney, Andrews returned to haemodialysis for approximately three months while remaining active on the transplant waiting list. In January 2026, medical staff successfully transplanted a kidney from a deceased human donor.
Researchers reported that the prior xenotransplantation did not complicate the subsequent human organ acceptance. No antibodies against human tissue or animal pathogens were detected, and the human kidney maintained stable function during subsequent medical evaluations, proving that animal bridges do not compromise future treatment options.
Broader Implications for Organ Shortages
Medical professionals view the outcome as an important proof-of-concept for addressing the chronic global shortage of human organs. More than 800,000 Americans and millions worldwide suffer from end-stage renal disease, while thousands die annually while waiting for compatible human donors.
“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,” said lead author Dr. Leonardo Riella. Researchers caution, however, that the results reflect intense specialist care and careful patient selection, meaning broader clinical trials will be necessary.
