For an excellent intro to what's wrong with xeno see: http://www.crt-online.org/wrong.html

Interestingly, Arthur Caplan the "bio-ethicist" from the University of Pennsylvania, quoted below, has been cited in the Gelsinger law suit against Penn for his advice pertaining to the trials in which the 18-year-old, with remember a disease controllable by diet and drugs, died a horrific death following gene therapy.
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AMA [American Medical Association] to consider ethics of xenotransplantation
http://www.ama-assn.org/sci-pubs/amnews/pick_00/prsd1211.htm
American Medical News
PROFESSIONAL ISSUES

The AMA House of Delegates is being asked to approve ethical guidelines for animal to human transplants when it meets in Florida this month.

By Vida Foubister, AMNews staff. Dec. 11, 2000.

Patients participating in xenotransplantation research may have to "waive the traditional right to withdraw from a clinical trial," according to the AMA's ethics committee.

The Council on Ethical and Judicial Affairs made that recommendation and several others in a report on the ethical implications of animal to human transplantation that will be presented to the House of Delegates at this month's Interim Meeting.

"Because of the unknown and essentially unknowable risk of transmission of infectious agents, patients who participate in xenotransplantation clinical trials are going to have to undergo a different kind of consent process than usually has been the case for other kinds of research projects," explained Robert Sade, MD, a member of CEJA.

Xenotransplantation has the potential of opening up a new pool of organs to draw from. But many critics say that not enough is known about the transmission of disease across species to proceed with clinical trials -- now or perhaps ever.

In its report, the council has essentially taken a "middle of the road" position. CEJA members don't believe the barriers to this technology are insurmountable. Still, they conclude that the public health risk is great enough to warrant that unique steps be taken.

"Until we know more, people should have to agree in order to get the possible benefit of this that they will not drop out of the study," said Herbert Rakatansky, MD, CEJA chair. "It's such a gigantic step to bridge the species gap."

However, requiring patients to waive their right to withdraw from a clinical trial isn't believed to be enforceable ethically or legally.

"A bedrock principle in research ethics has been the ability of a research subject to withdraw at any time," said Jeremy Sugarman, MD, MPH, director of the Center for the Study of Medical Ethics and Humanities at Duke University Medical Center in Durham, N.C. "While there are obvious public health concerns, there's good reason to pause before violating this principle."

Added Arthur Caplan, PhD, director of the University of Pennsylvania Center for Bioethics in Philadelphia: "Legally, you can't ask somebody to do what [CEJA] is suggesting. It's a fundamental right to be able to withdraw from research when you want to."

Currently, the thrust of this research is focused on pig organs. Pigs are physiologically similar to humans and can reproduce rapidly. There's also less risk of disease transmission and fewer moral concerns than with the organs of more closely related animals such as nonhuman primates.

In addition, almost 100 million pigs are slaughtered annually in the United States alone, said Robert P. Lanza, MD, vice president of medical and scientific development at Advanced Cell Technology Inc., a Worcester, Mass. biotechnology company. "If you can use it for sausages and bacon, the question is why can't you use it to save a life?"

The AMA has taken the stand that biomedical research using animals is essential to improving the health and well-being of humans. In its xenotransplantation report, it emphasizes that suchresearch "should continue to promote high standards of care and humane treatment of all animals."

Neal Barnard, MD, president of the Physicians Committee for Responsible Medicine, which has taken a stand against xenotransplantation, disagrees that such research can be compatible with the AMA's principle. "Raising animals for spare parts is not what anyone would call nice and kind and humane."

Other recommendations made by CEJA include allowing children and incompetent adults to participate only if they are terminally ill and lack other options and requiring the research sponsors to fund long-term surveillance and treatment of any complications. A Council on Scientific Affairs report on the scientific implications of xenotransplantation will also be presented at the December meeting.