Lawrence Fawcett, the second person to receive a heart transplant from a genetically modified pig, died six weeks after the experimental procedure, according to CNN.

The University of Maryland Medical Center, where the experimental procedure was performed, said the heart began to show signs of rejection in recent days.

Mr. Fawcett’s last wish was to make the most of what we have learned from our experience so that others can be assured of a chance for a new heart when a human organ is not available. He then told the team of doctors and nurses gathered around him that he loved us. He will be greatly missed,” said Dr. Bartley Griffith, clinical director of the Cardiac Xenotransplantation Program at the University of Maryland School of Medicine.

Fawcett, 58, was first admitted to the hospital on September 14 with symptoms of heart failure and underwent an experimental transplant six days later. His heart disease and pre-existing conditions made him unsuitable for a traditional human heart transplant.

“My only real hope left is to go with the pig heart, the xenotransplant,” Fawcett told the hospital in an internal interview several days before the surgery.

In the weeks immediately following the transplant, his doctors reported that he was making significant progress, including participating in physical therapy.

A month after the operation, doctors told him they thought his heart function was excellent. “We have no evidence of infections and no evidence of rejection at this time,” Bartley Griffith said at the time.

Doctors continued with an experimental antibody treatment to further suppress the immune system and prevent rejection. However, organ rejection is “the most significant challenge with traditional transplants involving human organs,” the University of Maryland Medical Center said in a statement.

In a statement about her husband’s death, Anne thanked those involved in her husband’s care.