Two years ago, Tim Andrews was so worn out that all he wanted to do was sleep. Diabetes and high blood pressure had destroyed his kidneys, and the frequent dialysis treatments were grueling. Though only 66, he had no energy, was too weak to walk, and had experienced two heart attacks. "I was dying," Mr. Andrews said.

A kidney transplant could have saved his life, but organs are in short supply. Roughly 90,000 people are on the waiting list, and on average, 11 people die every day while waiting, according to United Network for Organ Sharing. His rare blood type meant his odds of getting a matching human kidney were especially slim. So when he heard that doctors at Mass General Brigham were transplanting kidneys from genetically modified pigs, he reached out.

Mr. Andrews received a genetically modified pig kidney on Jan. 25, 2025, and lived with it for nine months. This year, he became the first known patient to receive a human donor kidney after a pig kidney transplant, a milestone described in a paper published Thursday in The Lancet. His case provides early proof that pig kidneys could offer "bridges" to human organ transplants.

The nine months with the animal organ were critical to getting his health back on track. The pig's kidney made urine and cleared waste 24/7, doing what dialysis does by machine only every other day. His diet improved, and he regained muscle mass. "It gave me life," Mr. Andrews said.