  
Chances of success with xenotransplantation recede
Last Updated: 2001-02-09 15:31:07 EST (Reuters Health)
By Richard Woodman
LONDON (Reuters Health) - Serious doubts about the prospects of successful pig-to-human organ transplants have been expressed by a Government expert advisory committee.
Several companies, including the UK's PPL, Switzerland's Novartis and America's Biotransplant Inc., are backing xenotransplantation research in the hope that animal organs can alleviate the severe shortage of human donor organs available for transplantation.
But the chances of success may be receding, according to the annual report of the UK Xenotransplantation Regulatory Authority, which was set up 3 years ago to regulate this new field.
The report, published this week by the Department of Health, notes that genetic modification of source animals--to "knock out" the gene responsible for hyperacute rejection and the include new genes needed to control later rejection-- is promising but is still in the "very early stages."
It adds: "Survival times in primate models do not yet provide substantive data that xenotransplanted organs are capable of sustaining life in humans. Researchers have indicated that this is related more to the inability to optimise immunosuppressive regimes rather than the problems of physiology. Nevertheless, the absence of data is a concern, not least because such data will only be obtained through further animal research."
The report also voices concern that eliminating all possible risks of transferring infectious agents as a result of xenotransplantation is impossible at present. "Moreover, the potential emergence of previously unrecognised organisms has to be borne in mind."
It concludes: "It seems therefore that the likelihood of whole-organ xenotransplantation--particularly for heart transplantation--being available within a clinically worthwhile time frame may be starting to recede."
The report notes that greater progress has been made in the development of cell transplant therapies for conditions such as Parkinson's disease, Huntington's disease, stroke, epilepsy, spinal injury and diabetes.
The authority has met with Genzyme, to discuss the firm's progress in xenotransplant cell therapies for Parkinson's disease, and the small UK firm Reneuron, which is developing murine and human neural stem cell lines for implantation into brains damaged by neurodegenerative diseases.
"The problem of rejection inherent in whole-organ xenotransplantation do not appear to represent such a major hurdle with these forms of treatment," the report says. "Immunosuppressive therapy...seems to be sufficient. Some anecdotal evidence of improvement in patients, notably in the treatment of Parkinson's disease, has been reported."
The authority is also cautiously optimistic about the progress being made in the development of bioartificial liver devices, in which the patient's plasma is passed through encapsulated porcine hepatocytes to treat fulminant liver failure.
The treatment, in phase II development by Circe Biomedical in the US and Europe, acts as a bridge either to recovery or to transplantation. "If success can be confirmed, a device utilising human cell lines would obviate the need to use porcine cells," the report authors note.
|
Copyright 2001 Reuters Limited. All rights reserved. Republication or redistribution of Reuters Limited content, including by framing or similar means, is expressly prohibited without prior written consent of Reuters Limited. Reuters Limited shall not be liable for any error or delays in the content, or for any actions taken in reliance thereon.
|
|
 Back To Transplant Wellness Center
| 
