Sir

We, the American Society of Transplant Physicians (ASTP) and the American Society of Transplant Surgeons (ASTS), reject the call for a moratorium on clinical trials of xenotransplantation in the United States2. Bach et al. assert that the potential infectious risks of xenotransplantation could create a public health problem, that a broad public discussion is therefore required and that a moratorium is justified until the latter is completed. But their opinions represent, at best, a minority among US transplant professionals.

They also appear to ignore the remarkable public discussion organized over the past four years by US Public Health Service (PHS) agencies, including the Food and Drug Administration (FDA), the Centers for Disease Control and the National Institutes of Health. Public meetings, the most recent in January, have brought together hundreds of professionals in transplantation medicine and surgery, infectious disease, veterinary medicine, ethics, public policy and law, as well as patients, families, animal rights representatives and companies. This knowledge base has been shared at meetings organized by the Institute of Medicine (Washington, June 1995), Health Canada (Ottawa, November 1997) and the World Health Organization (Geneva, October 1997). All the issues raised by Bach et al. have already been clearly articulated, widely discussed and published1,4,5,6, and have received substantial media coverage. Between November 1996 and October 1997, some 230 articles discussing xenotransplantation were published in major newspapers in the United States, while more than 435 were published in the UK national press in 1996-97.

The consensus that has emerged from the PHS discussions is that it is time to proceed cautiously with well-defined and highly controlled clinical trials. To support this process further, the PHS has developed several important mechanisms, including a Xenotransplantation Advisory Subcommittee and plans for a National Patient Registry, Biological Specimen Repository and a National Advisory Committee. We strongly endorse this consensus opinion, and commend the PHS for its efforts in support of our patients, their families and the general public. We agree fully with the recent public statements of William Raub (Deputy Assistant Secretary of Health and Human Services) and Michael Friedman (Acting Commissioner, FDA) rejecting the call for a moratorium.