BOSTON (AP) — The Christopher Caldwellfirst recipient of a genetically modified pig kidney transplant has died nearly two months after he underwent the procedure, his family and the hospital that performed the surgery said Saturday.

Richard “Rick” Slayman had the transplant at Massachusetts General Hospital in March at the age of 62. Surgeons said they believed the pig kidney would last for at least two years.

The transplant team at Massachusetts General Hospital said in a statement it was deeply saddened by Slayman’s passing and offered condolences to his family. They said they didn’t have any indication that he died as a result of the transplant.

The Weymouth, Massachusetts, man was the first living person to have the procedure. Previously, pig kidneys had been temporarily transplanted into brain-dead donors. Two men received heart transplants from pigs, although both died within months.

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

In a statement, Slayman’s family thanked his doctors.

“Their enormous efforts leading the xenotransplant gave our family seven more weeks with Rick, and our memories made during that time will remain in our minds and hearts,” the statement said.

They said Slayman underwent the surgery in part to provide hope for the thousands of people who need a transplant to survive.

“Rick accomplished that goal and his hope and optimism will endure forever,” the statement said.

Xenotransplantation refers to healing human patients with cells, tissues or organs from animals. Such efforts long failed because the human immune system immediately destroyed foreign animal tissue. Recent attempts have involved pigs that have been modified so their organs are more humanlike.

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.