Patient With Transplanted Pig Kidney Leaves Hospital for Home

The first patient to receive a kidney transplanted from a genetically modified pig has fared so well that he has been discharged from the hospital on Wednesday, just two weeks after the groundbreaking surgery.

The transplant and its encouraging outcome represent a remarkable moment in medicine, scientists say, possibly heralding an era of cross-species organ transplantation.

Two previous organ transplants from genetically modified pigs failed. Both patients received hearts, and both died a few weeks later. In one patient, there were signs that the immune system had rejected the organ, a constant risk.

But the kidney transplanted into Richard Slayman, 62, is producing urine, removing waste products from the blood, balancing the body’s fluids and carrying out other key functions, according to his doctors at Massachusetts General Hospital.

“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,” he said in a statement issued by the hospital. “Now it’s a reality.”

The procedure brings the prospect of xenotransplantation, or animal-to-human organ transplants, significantly closer to reality, said Dr. David Klassen, the chief medical officer for the United Network for Organ Sharing.

“Though much work remains to be done, I think the potential of this to benefit a large number of patients will be realized, and that was a question mark hovering over the field,” Klassen said.

Whether Slayman’s body will eventually reject the transplanted organ is still unknown, Klassen noted. And there are other hurdles: Successful operations would have to be replicated in numerous patients and studied in clinical trials.

The kidney transplanted into Slayman came from a pig genetically engineered by the biotech company eGenesis. Company scientists removed three genes that might trigger rejection of the organ, inserted seven human genes to enhance compatibility, and took steps to inactivate retroviruses carried by pigs that may infect humans.

More than 550,000 Americans have kidney failure and require dialysis, and over 100,000 are on a waiting list to receive a transplanted kidney from a human donor.

The treatment of kidney disease is already a huge expense. End-stage kidney disease, the point at which the organs are failing, affects 1% of Medicare beneficiaries but accounts for 7% of Medicare spending, according to the National Kidney Foundation.

This article originally appeared in The New York Times.