New class of drugs for erectile dysfunction unveiled

Scientists at Bristol-Myers Squibb have identified a promising new class of drugs that may yield strong candidates for the treatment of erectile dysfunction (also known as impotence) that may be more potent and have fewer side effects than the popular Viagra®, they say. The findings will appear in the April 6 print issue of the peer-reviewed Journal of Medicinal Chemistry, published by the American Chemical Society, the world's largest scientific society.

Although none of these compounds has been tested in humans, the researchers believe that the current study points toward promising new treatments for erectile dysfunction.

The first reliable oral medication for the treatment of erectile dysfunction, Viagra® (known generically as sildenafil) has surged in popularity since its introduction two years ago. It helps maintain an erection by blocking the action of an enzyme called phosphodiesterase type 5 in penile tissue.

Phosphodiesterase has several different forms. Researchers believe that sildenafil lacks specificity for certain forms of the enzyme -- notably, type 1 and type 6 -- and that non-selective blockade of these enzymes may trigger some of the drug's adverse side effects, especially facial flushing and visual disturbances.

In an effort to create a better drug, the researchers identified a novel class of phosphodiesterase inhibitors that act on the same target as sildenafil. Using an animal tissue model for erectile dysfunction, the researchers tested these compounds in the laboratory and found that they were as potent as sildenafil in achieving relaxation of the smooth muscle tissues. This corresponds to improved erectile function in humans, they say.

When tested against isolated phosphodiesterase enzymes, this series of drug candidates was more potent than sildenafil against phosphodiesterase type 5 as well as more selective against other phosphodiesterase enzymes, the researchers say. "More potency" means that less of the drug can be given to patients while achieving the same therapeutic effect; "more specificity" means that fewer side effects are likely to occur.