Editorial and reviews
Editorial Volume 354, Number 9191  13 November 1999
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Xenotransplantation: time to leave the laboratory

On Jan 25, 1997, The Lancet supported a delay in authorising the clinical application of xenotransplantation with the caveat, ". . . provided that productive discussion and not further dithering is the objective". Nearly 3 years on, there has been little dithering and a great deal of productive discussion and research, most of which has been conducted openly and with little perceptible input from experts suborned by commercial interests to bend opinion their way. It is now time to move on.

Further investigation of the feasibility of xenotransplantation has been intense. Initial fears about possible transmission of animal pathogens, in particular porcine endogenous retrovirus, to patients have receded, and processes for humanising pigs to abate rejection have been refined. A baboon has now survived for 40 days with a humanised pig heart, little different from the survival of early human donor-heart transplants. Possible applications of xenotransplantation have also spread from traditional targets of heart and liver replacement to other organs. At last month's 5th Congress of the International Xenotransplantation Society in Nagoya, Japan, several experiments were reported that promise new and useful applications to patients, including one which suggested that genetically modified pig cells can help regeneration of surgically damaged spinal cords in monkeys; and it was reported in May this year that parkinsonism in rats has been successfully treated by transplantation of fetal brain cells from cloned cows.

Current debates about the ethics, procedures, and safety of xenotransplantation exemplify how a scientific procedure, perceived by many as being ethically controversial, should be introduced. Inevitably, there are unhelpful contributions from extreme groups, an example of which is a glossy booklet produced jointly by the British Union for the Abolition of Vivisection and Compassion in World Farming, Animal organs in humans: uncalculated risks and unanswered questions. The cover features a man's face with his nose replaced by a pig's snout, an image which guarantees that the innocuous title hides arguments within that are specious and based on pseudoscience and selective quotation.

WHO has, for once, led imaginatively with an Electronic Discussion Group on International Xenotransplantation Policy Considerations (http://www.who.int/emc/diseases/zoo/meetings/ zenodg.html) with an international panel of moderators with precisely defined questions and objectives on concerns ranging from animal welfare to risk assessment. The Organisation for Economic Co-operation and Development, with 29 member countries, produced in March this year a readable and simple account of the issue. And in the UK and USA, exercises in testing public reaction are underway. No such solicitude for the public's opinion was shown when doubts were expressed about donor-organ transplantation or in-vitro fertilisation, two procedures that slid into routine use largely by default, despite bearing with them many ethical difficulties. The conclusion of these exercises is that there seems to be little enthusiasm for a blanket ban on xenotransplantation procedures.

Writing in the US Centers for Disease Control and Prevention publication, Emerging Infectious Diseases, nearly 4 years ago, Robert E Mitchler, director of heart transplant services, Columbia Presbyterian Medical Center, New York, USA, was in no doubt: "The question that remains is not how but rather when xenotransplantation should advance to the clinical area. Most uncertainties surrounding its advancement will only be answered in its undertaking".

It would be a pity if, after such a magnificent initiative to involve as many people and opinions as possible in the decision to permit xenotransplantation procedures, national regulatory authorities now dithered. The questions that remain, as Mitchler suggests, cannot be answered in the laboratory, but must now be tested in hospital. Many doctors poised to undertake such procedures have volunteers in the wings willing to take the possible risks. Governments should now make a decision. It is time to let clinicians begin the slow and painstaking journey of translating experiment into practice.

The Lancet
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