ByPeter Winter

BioWorld International Correspondent

KINGSTON, Ontario - Male erectile dysfunction (MED) is one of the largest growing markets for pharmaceuticals. Current estimates indicate that 66 million men worldwide suffer from some degree of MED, and by 2002 the market is expected to be worth approximately US$5 billion.

However, the sexual-dysfunction market is still at a comparatively early stage, and estimates indicate that less than 5 percent of men with erectile dysfunction are receiving some form of therapeutic intervention. Nevertheless, MED was dramatically brought to worldwide attention with the launch of New York-based Pfizer Inc.'s Viagra, the first FDA-approved oral therapy to treat this condition, earlier this year.

Now, a Canadian biotech company, Vaxis Therapeutics Corp., is hoping to capture a share of this huge sector. Vaxis plans to develop several products for treating male erectile dysfunction that will possess distinct competitive advantages over existing therapies.

Their technology was developed by researchers at Queen's University of Kingston, in Ontario, and, according to Michael Adams, a Queen's professor of pharmacology and toxicology and vice president of research at Vaxis, is based on an entirely new understanding of how blood circulation is controlled.

Viagra has provided welcome relief to millions of men. Vaxis says its approach goes beyond addressing just the immediate problem. Concerned with the underlying physiology rather than symptoms, the aim is to restore normal functioning and halt progression of the condition.

For many years, scientists have believed that the production of nitric oxide, a small gaseous molecule that is released from the endothelial cells lining the blood vessels, is responsible mainly for relaxing blood vessels. For example, studies showed that blocking nitric oxide production correlated with dramatically higher blood pressure levels.

However, Adams, Jeremy Heaton, Jim Banting and their research group have discovered that the change in blood pressure was not connected to the lack of nitric oxide, but to an unexpected increase in endothelin, a powerful vasoconstrictor.

When the levels of nitric oxide levels were lowered, the researchers discovered that the effects of endothelin went up, and accounted for about 90 percent of the blood pressure change, Adams said.

The Queen's scientists applied these basic research findings to their work on erectile dysfunction and found that a prolonged increase in the level of endothelin in the vasculature of the penis results in a constriction of blood vessels, thereby restricting blood flow. This cycle can exacerbate erectile dysfunction to the point that can ultimately lead to chronic impotence.

The team has demonstrated this causal relationship in laboratory studies and has shown that the effect can be reversed by using drugs to block the actions of endothelin. Vaxis controls U.S. and international patents based on this research, and is able to use the method to treat MED.

Vaxis has just signed a C$5 million investment deal with two of Canada's leading venture funds that target the healthcare sector: the Canadian Medical Discoveries Fund (CMDF), of London, Ontario; and Working Ventures Canadian Fund, of Toronto. Vaxis is testing drug compounds to determine which ones are best suited for use in treatment of MED. n