A 58-year-old man with terminal heart disease who received the world's second genetically-modified pig heart transplant has died nearly six weeks after the procedure, the medical center that carried out the surgery said.

Lawrence Faucette received the organ on September 20 and passed away on October 30, the University of Maryland Medical Center said in a statement on Tuesday.

He had been deemed ineligible for a human heart transplant because of his advanced medical conditions, including peripheral vascular disease. Though the transplant initially worked well, it began showing signs of rejection in recent days.

"We mourn the loss of Mr. Faucette, a remarkable patient, scientist, Navy veteran, and family man who just wanted a little more time to spend with his loving wife, sons, and family," said surgeon Bartley P. Griffith, who performed the transplant.

The latest experimental procedure was part of a growing field of research aimed at advancing cross-species transplants, or xenotransplants, involving animal organs genetically modified to become less likely to trigger rejection in humans.

It is hoped that eventually they will help address the human donor gap, with more than 100,000 people in America alone currently awaiting an organ.

David Bennett Sr was the first person to receive a gene-edited pig heart transplant in January 2022, carried out by the same medical team. 

He passed away after two months with the medical center ascribing his death to "a multitude of factors including his poor state of health" prior to the operation, though it was also later found that the organ was infected with a virus.

Muhammad Mohiuddin, the cardiac xenotransplantation program director, praised Faucette's contribution to science, adding: "We intend to conduct an extensive analysis to identify factors that can be prevented in future transplants."

Over the past two years, doctors have transplanted kidneys from genetically modified pigs into brain-dead patients.

The NYU Langone Hospital Transplant Institute in New York announced in September that a pig kidney transplanted into a brain-dead patient had functioned for a record-breaking 61 days.

Early xenotransplantation research focused on harvesting organs from primates — for example, a baboon heart was transplanted into a newborn known as "Baby Fae" in 1984, but she survived only 20 days.

Current efforts focus on pigs, which are thought to be ideal donors for humans because of their organ size, their rapid growth and large litters, and the fact they are already raised as a food source.