A gene-edited pig kidney kept Tim Andrews off dialysis for 271 days before his human transplant
Surgeons at Massachusetts General Hospital removed Tim Andrews's gene-edited pig kidney after 271 days, the longest a pig organ has bridged a patient to a human transplant, once thrombotic microangiopathy set in. A Lancet paper published on 3 September details the case; eGenesis, the transplant's biotech maker, says a fifth expanded-access patient has now passed 271 days and reached 285 days without dialysis, and the FDA has cleared a 33-patient formal trial for 2027.
Science··Morning
A gene-edited kidney bridges 271 days, then fails to blood clots
Surgeons at Massachusetts General Hospital transplanted a kidney from a gene-edited Yucatan miniature pig into Tim Andrews in January 2025, and removed it 271 days later after the organ failed — the longest a pig kidney has bridged a patient to a human transplant. Leonardo Riella and colleagues report in a paper published in The Lancet on 3 September that after Andrews's immunosuppression was reduced to treat an MRSA infection, damage appeared in the kidney's blood vessels. Wired reports that the surgical team traced the organ's failure to thrombotic microangiopathy, tiny blood clots forming inside the transplanted kidney.[1], [2]
A newer patient has already passed 285 days on the same program
eGenesis, the Cambridge, Massachusetts biotechnology company whose Crispr-edited pigs supplied the kidney, says a fifth patient given a kidney through the Food and Drug Administration's expanded-access pathway has now passed 271 days and reached 285 days without dialysis, a new high while Andrews's case was under review. eGenesis chief executive Mike Curtis says a second patient separately received a human kidney after eight months on a pig organ. More than 95,000 are on the kidney-transplant waiting list in the United States, while fewer than 28,000 transplants were performed in 2025; the FDA has cleared a formal trial of up to 33 recipients to begin in 2027.[2]
Five transplants in, the surgeon sees promise slowed by cost
Riella says his team has now performed five such transplants, with two more case reports due for publication this year, one from a patient who has already passed Andrews's nine months on a pig kidney. About 600,000 are on dialysis in the United States, he says, at a cost of roughly 100,000 dollars a year each. Michelle Willicombe at Imperial College London, who was not involved in the transplants, calls the underlying science incredible while expecting cost to slow how quickly the approach reaches more patients.[1]
