BETHESDA, MARYLAND--The transplantation of animal cells or organs into humans is getting a cautious go-ahead from U.S. health officials. At a meeting here today to help the government develop guidelines for the procedure, officials outlined their proposals for regulating and monitoring clinical trials and said the risk that the experiments might lead to new animal diseases infecting humans was too remote to halt clinical trials. But even as the government signaled that these trials will be allowed to continue, some experts said the risk is currently unknown and called for a moratorium.
Animal tissue transplants have shown some preliminary success as therapies for several diseases, including pig islet cells for treating diabetes and fetal pig brain cells for treating Huntington's disease, Parkinson's, and epilepsy. However, some scientists are concerned that new diseases might jump from donor animals to recipients--and perhaps to the public at large. In next month's issue of Nature Medicine, for example, xenotransplant researcher Fritz Bach of Harvard Medical school and eight colleagues call for a moratorium on clinical trials until the disease risks are more clear and have been publicly discussed.
But officials from the Food and Drug Administration (FDA), which has authority to approve all xenotransplantation trials as a new medical procedure, did not opt for a moratorium. Instead, they called for close monitoring of test results and proposed the creation of a national xenotransplantation advisory committee, a national registry of recipients, and an archive of tissue from patients and donor animals.
Some researchers at the meeting worry that the FDA's proposals don't go far enough. "I'm baffled, absolutely baffled," says virologist Jonathan Allan of the Southwest Foundation for Biomedical Research in San Antonio, that the proposals don't specifically ban nonhuman primate tissue transfers. Because primates such as baboons are genetically similar to humans, he says, their diseases--both known and unknown--are likely to be very dangerous. FDA officials argued, however, that their proposed regulations that require any donor animal to be free of known diseases rules out the use of baboons and other primates as transplant donors.