Just over two weeks after doctors placed a genetically edited kidney from a pig inside Richard Slayman, the 62-year-old is recovering at home and relishing “one of the happiest moments” of his life, according to a statement from the hospital that carried out the landmark four-hour surgery.

On March 16, Slayman became the first living person to receive such a transplant, according to doctors at Massachusetts General Hospital.

In a statement Wednesday, the hospital confirmed that Slayman had been discharged and was “recovering well.” The facility has credited “years of research, preclinical studies and collaboration” for the successful surgery.

“This moment — leaving the hospital today with one of the cleanest bills of health I’ve had in a long time — is one I wished would come for many years,” Slayman said in a discharge statement released by the hospital. “Now, it’s a reality and one of the happiest moments of my life.”

Slayman, who works for the Massachusetts Department of Transportation, battled kidney disease for more than a decade. He had gone on dialysis and survived a human kidney transplant in 2018 but had since grown desperately ill and was near despair, The Washington Post reported last month.

As doctors planned the milestone surgery, they were required to seek approval from the Food and Drug Administration, which allowed the surgery under its “compassionate use” rules. The approval is granted in cases where a patient has a “serious or immediately life-threatening disease or condition” and there are no alternative treatments, according to the FDA.

Human and pig kidneys are of similar size. To reduce the risk of Slayman’s immune system attacking the transplanted pig’s organ, researchers needed to make 69 different edits to the pig’s genetic code.

For the more than 550,000 kidney patients in the United States receiving dialysis, Slayman’s story may offer a glimmer of hope. Leonardo V. Riella, medical director for kidney transplantation at Massachusetts General, has said he hopes that, as this science advances, dialysis will one day become obsolete.

Slayman said in his statement he was “excited to resume spending time” with his loved ones, “free from the burden of dialysis that has affected my quality of life for many years.”

As of February 2023, 88,658 people were on the waiting list for a kidney transplant in the United States, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

The institute notes that White people were more likely to receive a transplant within five years, compared to Black, Hispanic, and Asian people. Experts hope medical advances, including using pig kidneys, can help address this inequity, and address the gap between those waiting for transplants and the short supply of human organs available.

New technologies have been credited for recent advances in the field. They include CRISPR, the gene-editing tool recognized in 2020 with a Nobel Prize in chemistry, which can modify organs to make them less foreign to a recipient, reducing the chance of rejection.

Some scientists have also transplanted organs from animals into donated bodies, as part of their research into Xenotransplantation — the process of implanting organs from one species into another. They hope their findings will result in the FDA one day allowing formal Xenotransplant studies, the Associated Press reported.

In recent years, two patients have died after receiving organ transplants from animals.

In 2022, the first patient in the world to receive a genetically modified pig’s heart died around two months after the procedure, according to officials at the University of Maryland Medical Center. The patient, David Bennett Sr., suffered multiple complications, and traces of a virus that infects pigs were also found in his new heart, The Post reported.

In 2023, another patient died six weeks after receiving a pig heart transplant. Before the surgery, Lawrence Faucette was dying of heart failure and was deemed ineligible for a human heart transplant due to his advanced medical conditions. The pig transplant procedure was his last chance at life.

While Faucette initially showed “significant” signs of progress, his new heart began to show “signs of rejection” in the weeks that followed, officials at the University of Maryland School of Medicine said.