New FDA Guidance on Xenotransplants Acknowledges Danger to Public Health
On April 6th, the U.S. Food and Drug Administration (FDA) published a "guidance for industry" in the Federal Register on "Public Health Issues Posed by the Use of Nonhuman Primate Xenografts in Humans." In the document, the FDA acknowledges that nonhuman primates can transmit a host of viruses to humans, including Ebola and the simian equivalent of HIV; and that transplanting live cells, tissues, and organs from such animals to humans would expose patients, their close contacts, and the public at large to "significant infectious disease risk(s)." Yet the FDA stopped short of banning nonhuman primate xenografts, encouraging "further scientific research" into the risks.
"The risks inherent in xenotransplantation have already been well-described in the scientific literature," says Alix Fano, Director of the Campaign for Responsible Transplantation, a coalition of 70 international organizations opposing animal-to-human organ and tissue transplants. "If nonhuman primate xenografts are as remotely dangerous as the FDA claims, the agency should have simply banned them. We are also very disappointed that the FDA did not address the danger posed by pigs - the source animals of choice at this point. This guidance does nothing to stop continued work with pigs, and they are just as dangerous," says Fano
CRT believes that the FDA purposely excluded pigs from the guidance to appease biotechnology companies like Novartis and Alexion who have poured millions of dollars into developing herds of transgenic pigs for xenotransplants. In what CRT views as a conflict of interest, these companies have worked closely with federal agencies like FDA and the Centers for Disease Control (CDC) to develop xenotransplantation, despite the dangers it poses to the public.
Many scientists agree with CRT, including French virologist Claude Chastel who says that, "Pig viruses are just as dangerous as nonhuman primate viruses." There are over 25 diseases from pigs that can infect humans and new ones keep surfacing, including Porcine Reproductive and Respiratory Syndrome virus, and paramyxovirus. The "Nipah" virus, discovered in Malaysia six months ago, spread from pigs to humans, infecting 229 people - causing high fever, aches, and convulsions, killing 111, and leading to the mass slaughter of 640,500 pigs. The CDC's Tom Skinner said the virus had "never been seen before." A similar illness afflicted 11 slaughterhouse workers in Singapore last month. That may be why researchers at the Mayo Clinic are testing 300 slaughterhouse workers in the U.S. for signs of infection by pig viruses, including the Porcine Endogenous Retroviruses (PERVs), found throughout the pig genome, that have infected human cells in test tubes.
The influenza virus of 1918, which resembled a common swine flu, killed more people in modern history than any other epidemic including AIDS and the Black Plague. A new influenza strain (H3N2), which swept across Northern China to Hong Kong last year, has been spreading among U.S. pig herds.
"We are being told by Novartis and the CDC that pig xenotransplants are "safe" because a preliminary study of 160 patients exposed to pig cells and grafts showed no evidence of PERV infection" says CRT's Fano. "But a year-long study on a small group of patients is not proof of safety, or efficacy. The Novartis/CDC study, among other things, fails to account for long disease latency periods."
Indeed, a January 20, 1999, study in the Journal of the National Cancer Institute reported that Simian Virus 40, (SV40), which contaminated polio vaccine in the early 1960s, was regarded as harmless, until recently. Scientists now say that initial studies may not have been conducted over a long enough period, and new highly sensitive tests have detected the presence of SV40 in different types of human tumors, perhaps responsible for 1,000 new human cancers each year.
"History could repeat itself if we allow xenotransplants to go forward. The new Public Health Service guidelines on xenotransplantation, due out this summer, will never eliminate risk, and no pig will ever be virus-free," says Fano. "We know very little about the pathogenicity of pig viruses, and yet the FDA is continuing to approve clinical trials with pig organs and cells before the data are in," she says. "For the FDA to "prohibit" nonhuman primate xenografts on the one hand, but allow pig xenografts on the other is irrational public health policy."
In January 1999, the Council of Europe, representing 40 European countries, recommended a world-wide ban on xenotransplantation. In December 1998, CRT filed a legal petition with the Department of Health and Human Services (HHS) asking for a ban on all uses of the technology. The government has until June 10th to respond. In the meantime, Fano has asked the FDA to include a CRT official on a new federal xenotransplantation advisory committee. "CRT represents over 2 million people. This is FDA's chance to prove that it really does want public input on this issue," she says.