NEW
DRUGS FOR IMPOTENCE 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 appear in a recent 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.
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