BioWorld International Correspondent

TORONTO - Stem cell research offers exciting prospects for new treatments, but the challenge is to find safe and effective, but also scaleable, approaches that will be available a reasonable cost to the large number of patients who could benefit.

Not only that, those stringent requirements must be met in the least ethically challenging way, Simon Best, president and CEO of Ardana Biosciences Ltd. in Edinburgh, Scotland, told delegates at the BIO 2000 International Exhibition & Convention here Monday at a session titled "Frontiers in Stem Cell Research."

"The heat and emotion of debate on stem cell use is more heated [in the U.S.] than anywhere else," he said. But at this stage of the research it is necessary to explore all possible approaches to stem cell therapy, including using embryonic stem cells, he said.

Lord Sainsbury, the UK minister for science, said the UK government had recognized the potential contribution stem cell therapy could make to treat a range of diseases, but also acknowledged that there are differing views on the ethics of the research. Following extended debate the UK government decided to allow stem cell research using embryos.

"We therefore have a situation in the UK where we have a clear, stable regulatory framework which allows therapeutic cloning, because of the huge benefits," he said.

For now, researchers in the U.S. who want federal funding are limited to working with embryonic stem cell lines derived before Aug. 9, 2001. This so-called "Bush Database" now numbers 80 cell lines, according to Mark Rohrbaugh, head of technology transfer at the National Institutes of Health, who is responsible for negotiating rights with the owners of the cell lines.

However, Alan Colman, of ES Cell International Pte. Ltd. in Singapore, one of the three companies currently supplying embryonic stem cell lines, said most of the 80 consist of a frozen cell mass and it is not clear if they will produce viable cell lines. "It sounds easy, but growing these cells is enormously difficult," he said. "Probably only 20 to 25 will make it through."

In addition, most of the cell lines in the Bush Database have been raised on a mouse cell substrate, meaning that if they do advance as far as therapeutic entities the FDA would treat them as xenotransplantation products.

ES Cell International recently succeeded in growing stem cell lines on human feeders, meaning they will not be treated as xenotransplant products and thus will supersede most of the 80 lines in the Bush Database.

Colman added that human embryonic stem cells are now showing the same versatility that has already been demonstrated using mouse embryonic stem cells, animal models have shown the efficacy of the approach, and therapeutically acceptable human stem cell lines are now being made.

Despite this encouraging progress, Martin Edwards, CEO of ReNeuron Ltd., a stem cell company in Guildford, UK, said there remains significant hurdles in product development of stem cells. "The lack of precedent leads to uncertainty," he said.

In particular, GMP issues are not defined, there is concern at the possibility of tumor formation, and although the in vivo models are good it is not certain they will be valid in human therapy.