Massachusetts General Hospital said it’s the first time a genetically modified pig kidney has been transplanted into a living person. Previously, pig kidneys have been temporarily transplanted into brain-dead donors. Also, two men received heart transplants from pigs, although both died within months.

The experimental transplant was done at the Boston hospital on Saturday. The patient, Richard “Rick” Slayman of Weymouth, Massachusetts, is recovering well and is expected to be discharged soon, doctors said Thursday.

Slayman had a kidney transplant at the hospital in 2018, but had to go back on dialysis last year when it showed signs of failure. When dialysis complications arose, his doctors suggested a pig kidney transplant, he said in a statement released by the hospital.

“I saw it not only as a way to help me, but a way to provide hope for the thousands of people who need a transplant to survive,” said Slayman.

The announcement marks the latest development in xenotransplantation, the term for efforts to try to heal human patients with cells, tissues, or organs from animals. For decades, it didn’t work — the human immune system immediately destroyed foreign animal tissue. More recent attempts have involved pigs that have been modified so their organs are more humanlike — increasing hope that they might one day help fill a shortage of donated organs.

More than 100,000 people are on the national waiting list for a transplant, most of them kidney patients, and thousands die every year before their turn comes.

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