"Doctors can't fully explain the death of the first recipient of a genetically modified pig heart, but they offered several theories in a new study -- and said clinical trials of pig-to-human organ transplantation should begin despite the continuing mystery.
David Bennett, a 57-year-old handyman from Hagerstown, Md., received the heart in an experimental operation in January at the University of Maryland Medical Center in Baltimore and died two months later. The surgery -- an attempt to extend the life of a desperately ill patient who had been kept alive for weeks on a machine that took over the functions of his heart and lungs -- came after the U.S. Food and Drug Administration issued a special emergency authorization for it.
The authors of the study, published Wednesday in the New England Journal of Medicine, attributed Mr. Bennett's death to heart failure. But they were unable to pinpoint why the pig heart thickened and lost its pumping ability after seven weeks.
"It is still a mystery," said Muhammad M. Mohiuddin, a professor of surgery at the University of Maryland School of Medicine and one of the authors of the paper.
One possible explanation, the researchers said in the paper, is that the transplanted pig heart was attacked by human antibodies administered to Mr. Bennett in an effort to treat infections.
Another possible factor in his death could have been temporary discontinuation of treatment with an immune-suppressing drug that was given to prevent rejection of the pig heart, according to the researchers. They said the discontinuation, necessitated by a precipitous drop in his Mr. Bennett's white blood cell count, could have left the heart vulnerable to rejection.
Another possible explanation was that the pig heart given to Mr. Bennett was impaired by a pig virus, which was detected about 20 days after the surgery. There is no evidence that the virus infected Mr. Bennett, according to the researchers, but its presence in the pig heart could have caused inflammation that contributed to the cascade of events that led to his death.
Previous research involving the transplantation of pig organs into baboons showed that a recipient animal's long-term survival can be limited by the presence of pig cytomegalovirus, or CMV, the virus found in the heart Mr. Bennett received.
Scientists conducting experiments on interspecies organ transplantation, or xenotransplantation, said the fact that Mr. Bennett's body didn't immediately reject the heart -- and that he lived for two months following the surgery -- indicated that it now made sense to consider launching clinical trials.
"Mr. Bennett's life should accelerate the move to trials rather than his death slowing things down," said Dr. Allan Kirk, chair of surgery at Duke University School of Medicine and a transplant surgeon who wasn't involved in Mr. Bennett's surgery. "The question holding the field back was, can a pig organ provide life support for a human -- and the answer is yes."
The FDA is reviewing the study findings, a spokeswoman for the agency said, adding that applications for xenotransplantation studies are evaluated on a case-by-case basis.
University of Maryland researchers and Revivicor, the Blacksburg, Va., company that supplied Mr. Bennett's pig heart, hope to meet this summer with FDA officials to discuss the possibility of a clinical trial, Dr. Mohiuddin said.
Researchers at the University of Alabama at Birmingham are also seeking FDA approval to launch a clinical trial, according to Dr. Jayme Locke, director of the university's Heersink School of Medicine's Comprehensive Transplant Institute.
The Alabama program reported earlier this year that it had successfully transplanted a pair of pig kidneys into the body of a brain-dead person.
Later this month, the FDA is holding a public advisory committee hearing on xenotransplantation.
Mr. Bennett's case has been closely watched by the wider transplant community, which for decades has tried to advance xenotransplantation as a possible fix for the chronic shortage of human donor organs.
More than 100,000 patients are on the waiting list for hearts, kidneys and other organs at any given time, according to the United Network for Organ Sharing, which helps allocate donor organs in the U.S. More than 6,000 die every year before getting one, according to the nonprofit organization." [1]
1. U.S. News: Pig-Heart Death Remains a Mystery
Marcus, Amy Dockser.
Wall Street Journal, Eastern edition; New York, N.Y. [New York, N.Y]. 23 June 2022: A.3.
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