Rules Guide Implanting Animal Cells Fda Weighs Risk Of New Disease Against Benefit For The Ailing

The Food and Drug Administration issued the first federal guidelines Friday for the promising yet risky field of transplanting animal tissue into humans.

The proposed guidelines cover a broad range of therapies, from whole-organ procedures like the famous 1984 “Baby Fae” baboon heart transplant to less-known but potentially valuable treatments for diabetes and other ailments using modified cells from cattle, pigs and other animals.

The logic behind “xenotransplantation” has long appealed to the medical community. Thousands of Americans die each year awaiting organs because there are about 50,000 needy patients and only 5,000 donors.

If the supply pool could be expanded to include animals, demand could be met many times over, researchers say.

At the same time, researchers worry about how humans might react to animal-borne viruses and bacteria. Monkeys can spread the Ebola virus to humans, and primates carry simian immunodeficiency virus, closely related to the human AIDS virus. Scientists are exploring possible links between mad cow disease and Creutzfeld Jakob disease in humans.

Many transplant procedures require suppression of the recipient’s immune system, increasing the risk of transferred diseases, known as “zoonoses.”

Researchers generally predicted that the proposed safeguards would encourage expanded use of animal transplants.

“I see these guidelines as a show of support from the government, from society, that the need is definite and no one really wants to stop science cold,” said Dr. Steven Deeks of the University of California, San Francisco, who recently transplanted baboon bone marrow into an AIDS patient.

FDA Commissioner David A. Kessler said Friday that the new guidelines were crafted to strike the “right balance” between the promise of xenotransplantation and its potential perils. “This has to be one of the hardest balances to achieve,” Kessler said. “We are dealing with very real risks and very real unknowns.”

However, he said, “we’ve not been able to meet the needs of a lot of human suffering through donations. Because that problem is very real it’s okay, I feel, to take some risks.”

The proposed guidelines, developed with the Centers for Disease Control and Prevention and the National Institutes of Health, were published in Friday’s Federal Register, call for researchers to screen animals very carfully for diseases that might make their way into human recipients.

Researchers would also preserve blood and tissue samples from the animal and the recipient, and monitor patients for emerging diseases. After a 90-day comment period, a final rule will be published.

John Allan, a primate virologist at the Southwest Foundation for Biomedical Research, opposed the plan.

“It’s irresponsible to do these types of experiments when the downside is the possibility of creating greater suffering through the spread of infectious diseases,” said Allan, who served on an FDA advisory panel that studied xenotransplantation.

“The problem is, you can’t make it safe,” said Allan, who warned that not all zoonoses are known, and some could take years to develop.

Some animal rights activists also sharply criticized the proposal.

Dan Mathews, director of campaigns for People for the Ethical Treatment of Animals, said the “Frankenstein science … could pave the way for a plague worse than AIDS.”

Mathews said appropriate funding for human donor programs could solve the problem: “There’s no shortage of available human organs - they’re just being buried.”

But many representatives of the biomedical industry applauded the agency’s action. “We think the FDA is taking a reasoned position,” said Seth A. Rudnick, CEO of Providence, R.I.-based CytoTherapeutics, which plans to implant small packets of fetal calf adrenal cells to relieve the intense pain of late-stage cancer patients.

“They’ve taken a very responsible and balanced approach,” said Patrick Soon-Shiong, president of California-based Vivorx, a company about to begin trials to treat diabetics with pig pancreas cells.