A chronic kidney failure patient who could hardly live a normal life without dialysis received a kidney transplant and regained health. It was not because of good luck in finding a kidney for transplant in time. A pig kidney with some genes altered to block immune rejection served as a bridge, extending life for nine months until the transplant surgery.
A nephrology team led by Professor Leonardo Riella at Massachusetts General Brigham said in the Lancet on the 4th that Tim Andrews, 67, a chronic kidney failure patient, lived without dialysis for 271 days on a previously transplanted pig kidney until he underwent a kidney transplant in January.
The medical community said the result shows that xenotransplantation using other animals can solve the chronic shortage of organ donations. Even if xenogeneic organs cannot fully replace human organs, they can buy time until a transplant organ is found. In other words, it served as a stepping stone leading to a human organ transplant.
◇ Editing 69 genes to prevent immune rejection
On Jan. 25 last year, Andrews received a pig kidney with some genes edited. His original kidneys had lost function and were removed two days earlier. The pig organ transplanted into Andrews was provided by eGenesis, a biotech company in Cambridge, Massachusetts. The company was founded by George Church of Harvard University, an authority in xenogeneic gene editing.
eGenesis edited 69 pig genes to fundamentally block immune rejection. The gene editing proceeded in three main directions. Using CRISPR-Cas9, an enzyme complex that cuts only desired genes in DNA, the team first removed three pig antigen genes that trigger a hyperacute immune response.
They also neutralized pig-specific viral genes that could pose risks if transmitted to humans. At the same time, they inserted seven human genes so the transplanted kidney could coexist with the human body without issues. In short, they created a humanized pig kidney.
eGenesis said that since March 2024, five chronic kidney failure patients have received the gene-edited EGEN-2784 pig kidney at Massachusetts General Brigham. Of these, three maintained kidney function for more than eight months without dialysis. Among them, Andrews set a record by surpassing nine months without dialysis on a pig kidney.
Andrews later had the failing pig kidney removed, endured on dialysis again, and 82 days later received a human kidney transplant. Another patient also switched to a human kidney. The relay from a pig kidney to a human kidney succeeded.
Building on this success, eGenesis said it will expand clinical trials. The U.S. Food and Drug Administration (FDA) approved a clinical trial to transplant eGenesis' gene-edited pig kidneys into 33 kidney failure patients ages 50 to 77 on the kidney transplant waitlist.
◇ Overcoming the limits of dialysis to buy time until transplant
Chronic kidney failure patients supplement lost kidney function with dialysis. Dialysis removes blood, filters impurities with a medical device, and returns it to the body. In principle it substitutes for the kidney's role, but in practice dialysis replaces only one-tenth of kidney function. Even with five-hour sessions three days a week at the hospital, toxins and minerals keep building up, damaging blood vessels and raising the risk of heart disease.
The solution is a kidney transplant, but supply falls far short. In the United States alone, more than 800,000 people suffer from end-stage kidney disease, but kidney transplants totaled 28,000 in 2024. eGenesis said that while a humanized pig kidney created through gene editing cannot perfectly replace a human kidney, it can keep patients healthy until a human organ is found. Andrews is the proof.
Mike Curtis, CEO of eGenesis, said, "Andrews suffered two heart attacks during dialysis and relied on a bed or wheelchair, but within a few days of receiving the pig kidney, he was able to walk on his own," and "when the pig kidney was later removed and he returned to dialysis, he was in a much healthier state than nine months earlier."
This is not the first time a pig organ has served as a bridge to actual transplant surgery. In March, the journal Nature reported that a Chinese patient on the brink of death from worsening liver function endured three days on a pig liver before liver transplant surgery. A medical team at Xijing Hospital of Air Force Medical University in Xi'an, China, connected a patient with liver failure to an extracorporeal circulation device containing a pig liver, sustaining life until the actual liver transplant.
According to Dr. Lin Wang, the surgeon who performed the procedure, the 56-year-old man had severe liver damage from hepatitis B, other liver diseases, and alcohol, and his liver function was rapidly deteriorating. After extracorporeal circulation using a pig liver, the patient received a human liver transplant in January and is now recovering.
References
Lancet (2026), DOI: https://doi.org/10.1016/S0140-6736(26)01295-X