Xenotransplantation is typically defined as the transfer of a body organ from one species to another. The perceived need for xenotransplantation has arisen as the result of a worldwide shortage of human organs for transplantation coupled with a low donation rate, increased demand with medical advances and a lower incidence of road death.
Xenotransplantation also covers the use of cells for therapeutic purposes. Areas of potential therapeutic use are in the treatment of neurodegenerative diseases such as Alzheimer's disease and metabolic diseases such as diabetes.
Current studies in respect of diabetes focus on the transplantation of self-regulating insulin producing pig pancreatic cells which may revolutionise the treatment of the disease. Diabetes is the fifth leading cause of death in the developed world and is tipped to become the main cause within the next two decades.The Concerns
The greatest perceived risk of allowing xenotransplantation trials in New Zealand relates to the introduction of porcine endogenous retrovirus ("PERV") into the human population.
In August 1998, The Lancet published three research articles, two of which reported no infection in people who had actually received living pig tissue and a third which showed that PERV shed by pig kidney cells in petri dishes could infect human cells. Although the latter publication raised the possibility that the virus could be transferred from pigs to humans, it is important to recognise that this observation is based on experiments performed in the laboratory rather than observations that show that viral infection actually occurs in any particular species.
Subsequent testing has failed to reveal any evidence of PERV infection. Reports suggest that a significant number of patients have been exposed to porcine tissues with no evidence of retroviral infection and recent studies show that 160 patients exposed to living porcine cells for periods of up to 460 days tested negative for porcine virus transmission."Despite the evidence for extended exposure to pig cells and despite concomitant immunosuppressive therapy, we were unable to detect markers of PERV infection in any patient." Lancet 1998; 354: 695-99 The Regulation of Xenotransplantation in New Zealand
Xenotransplantation is currently regulated in New Zealand under the Medicines Act 1981. Any clinical application involving xenotransplantation must therefore meet the same rigorous requirements for safety as other clinical procedures.
The difficulties associated with obtaining the appropriate approvals to undertake xenotransplantation are exemplified by the fact that every one of the most recent applications involving xenotransplantation has been declined by the Ministry of Health because of concerns about retroviral infection. The position that seems to have been adopted is to proceed with caution until sufficient dialogue has taken place to establish appropriate policies and guidelines.The Most Recent Instalment
The most recent instalment in the xenotransplantation debate comes in the form of Supplementary Order Paper 231 ("SOP 231") which was introduced into the House, under urgency, on the last day of Parliament's final session last year. SOP 231 is attached to the Hazardous Substances and New Organisms (Genetically Modified Organisms) Amendment Bill ("HSNO Amendment Bill") which was introduced into the House in response to the Royal Commission Report on Genetic Engineering.
SOP 231 bans specified biotechnical procedures such as germ cell-line and xenotransplantation procedures. Germ cell-line procedures are specifically defined as the artificial insertion or injection of a genetically modified embryo into a human being. Xenotransplantation is defined more broadly as:
(a)...a medical procedure that involves the insertion or injection into any human being of any matter that consists of, or includes, living biological material of an animal, whether or not that biological material also includes the biological material of a human being.
(b)...the transfusion into any human being of any human blood or any human body fluid if the blood or the fluid has, as part of the biotechnical procedure, been in contact with living biological material of an animal.
It has been suggested that these amendments will effectively lead to a moratorium on xenotransplantation using both genetically modified and unmodified cells for a period of between 2 and 4 years.
The introduction of such a broad prohibition on xenotransplantation in response to the Royal Commission Report is concerning. It is generally accepted that Royal Commissions must act strictly within the terms of their Warrant. The Warrant issued to the Royal Commission on Genetic Engineering stipulated, in its Terms of Reference, that the Commission should receive representations upon, inquire into, investigate, and report upon:
1. the strategic options available to enable New Zealand to address now and in the future, genetic modification, genetically modified organisms and products; and
2. any changes considered desirable to the current legislative, regulatory, policy or institutional arrangements for addressing, in New Zealand, genetic modification, genetically modified organisms and products.
Although the Royal Commission did deal with the issue of xenotransplantation, its recommendations should only be considered to apply to the transplantation of genetically modified cells. To use the Royal Commission Report to justify amendments to the HSNO Amendment Bill, which effectively ban xenotransplantation using unmodified cells, would not be appropriate."A Commission's Warrant gives it the authority to run an inquiry in a certain way and into particular matters. Acting outside of its authority can result in a legal challenge. Commissions must be particularly careful to inquire into only what they are directed to by their Terms of Reference" The Department of Internal Affairs So What is the Alternative?
Although Canada and Sweden currently have a moratorium in place which bans xenotransplantation until guidelines have been agreed, a number of countries including the United Kingdom, the United States, Canada, Sweden, and Spain have published draft guidelines to minimise the risk. According to the Ministry of Health, New Zealand is actively participating in the international dialogue on xenotransplantation.
Given the intensive international debate surrounding the issue and the likelihood of some breakthrough in the debate in the near future, it may be more appropriate to put the moratorium on hold - especially when there are already effective regulatory procedures in place.
This is a general summary only and should not be taken as a substitute for specific advice.Contacts
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