All information collected thereafter will be applied when ready for the next xenograft patient. This includes clues about how to prevent problems that may have contributed to heart failure, including a reaction to medication aimed at preventing rejection.
“We are still trying to figure out what went wrong; we don’t have a single answer,” said Muhammad M. Mohiuddin, co-lead of the porcine heart study and professor of surgery and scientific/program director of the cardiac xenotransplantation program at the medical school.
“But we don’t see it as a setback,” he said. “We consider that he lived the surgery of the first victory. When he seemed to recover and be fine for two months, we really thought he was a huge success. If we could have identified the reason why his heart suddenly gave out, he might have left the hospital.
An autopsy revealed that Bennett’s body showed no traditional signs of heart rejection. Instead, doctors saw thickening and then stiffening of the heart muscle, possibly a reaction to a drug used to prevent rejection and infection. This made him unable to relax and fill with blood like he’s supposed to.
According to the doctors’ study, published in June in the New England Journal of Medicine, they also found DNA from a latent infection in the specially bred pig that escaped precautions and screening. It is still unclear whether this contributed to the heart failure.
Bennet, 57, had been bedridden and hooked up to a heart-lung bypass for eight weeks with end-stage heart failure before the transplant with the genetically modified pig heart. He was ineligible for a traditional heart transplant, and federal regulators granted him a “compassionate use” exemption to have the experimental pig heart transplant. These animal organ transplants are not approved by the Food and Drug Administration.
For now, any such transplant will be considered “on a case-by-case basis,” according to a statement from an FDA spokesperson to the Baltimore Sun.
The agency wouldn’t say if and when regulators would allow human trials, which usually means more transplant patients, more hospital sites and collecting data in an effort to approve the procedure. . The Wall Street Journal, citing “sources familiar with the matter,” reported last week that the FDA was drawing up such plans.
FDA officials acknowledged to The Sun the need to address the shortage of organs for transplant.
“Xenotransplantation represents an option to help address the shortage of human allografts and organs for transplantation,” according to an FDA spokesperson.
But the FDA also cited the complexity and risk of animal transplants, including the transfer of infections, and the need to “carefully weigh” those risks against the potential benefits of any trial.
“Overall, the FDA will not authorize the use of an investigational product unless it believes these risks are appropriately minimized and acceptable for the clinical situation,” the spokesperson said. “Because of the potentially serious public health risks from possible zoonotic infections, the FDA has instituted policies such as long-term patient surveillance and blood donation bans to mitigate the risk of infectious disease transmission. “
Mohiuddin said the doctors had been in contact with the FDA about the human trials, but said there would be more animal studies in the meantime.
“I think the submissions made to the FDA by people in the field indicate that the best way forward is through a human clinical trial,” he said. “We look forward to seeing how the FDA responds to this entry and if they issue further guidance on this. Going forward, we’re doing more primate studies to see what more we can learn.
But Mohiuddin said doctors already knew Bennett’s transplant discoveries would lead to changes in the practices and techniques of future human transplants.
Patients and their families have contacted him and other doctors since the announcement of the transplant, but there is no deadline to seek approval for another transplant.
“There is a patient population that could benefit from it, and many have come forward, volunteered for the procedure,” he said. “Before satisfying someone else, we must be convinced that what we have learned can be applied to the next.”
The transplant is the result of a $15.7 million research grant from Virginia-based biotech company Revivicor to study its genetically modified pig UHearts in baboons.
About 110,000 Americans are waiting for organ transplants, and more than 6,000 die each year while on the list, according to federal figures.