Race Is Under Way In Bid To Top Viagra's Enormous Success
June 02, 1998 12:05 AM
By Robert Langreth and Rochelle Sharpe, Staff
Reporters of The Wall Street Journal
SAN DIEGO -- Viagra is just the beginning.
In the wake of the impotence pill's enormous success,
drug and biotechnology companies are racing to develop
a slew of new products that have fewer side effects than
Viagra or could offer treatments to people who can't use
the drug or don't respond to it.
Despite its reputation as a miracle pill, Pfizer Inc.'s
Viagra works for only about 70% of those who take it.
Many others who would like to take Viagra cannot
because they are also using nitrates, common heart
medications that can cause serious cardiovascular side
effects when combined with Viagra.
But impotence experts at the annual meeting of the
American Urological Association here said help is on the
way. Several drugs under development work by
completely different mechanisms than does Viagra. They
include an old blood-pressure medication that is being
resurrected as an impotence pill by Zonagen Inc. of The
Woodlands, Texas, and another drug, apomorphine,
being developed by TAP Holdings Inc., of Deerfield,
Ill., that, unlike Viagra, acts directly on the brain to
facilitate erections.
Either might be combined with Viagra to make erections
last longer. Both these drugs may also work more
quickly than Viagra, which takes about 45 minutes to
kick in.
In the long term, scientists at the conference said the
brave new world of gene therapy might someday allow
doctors to cure impotence for months at a time with one
injection of new genes into the penis. The researchers'
exuberance about future treatments was so strong that at
times they sounded as if they were starring in an
infomercial for impotence drugs.
Still, urologists conceded that it will be hard to top
Viagra. "Viagra isn't the perfect drug, but it is pretty
close," said urologist Ira Sharlip, a leading impotence
expert based in San Francisco. He said the most
important use of the new drugs would most likely be in
combination therapies with Viagra. "If you can take two
or three drugs with different mechanisms of action you
might be able to take a lower dose of each and have an
enhanced effect," he said.
Results of human studies of several new medications are
scheduled to be disclosed today. Researchers are
expected to announce that Zonagen's Vasomax
produced significantly better results in about 40% of the
several hundred patients who have tried it, and scientists
testing the drug say it can be used in patients taking
nitrates. Vasomax works by relaxing muscle cells in the
groin, easing blood flow to the penis. Zonagen, which is
collaborating with Schering-Plough Corp. to develop the
drug, is expected to file for government marketing
approval this month. (The drug was approved for use in
Mexico last week.)
But Zonagen's clinical trials have been controversial, and
some short sellers of the stock have attacked the tests as
flawed. Moreover, at high doses the drug can cause low
blood pressure.
Researchers at the conference were also intrigued by
TAP Holdings' apomorphine. This oral drug acts directly
on the brain, stimulating nerve signals to produce
erections. It is effective on roughly 60% of those who try
it, researchers said. The main drawback of the drug,
used as a vomit-inducing agent in higher doses, is that it
nauseates some patients -- a big deterrent to romance.
TAP, a joint venture of Abbott Laboratories and
Takeda Chemical Industries Ltd., of Japan, plans to file
for approval of the drug by 1999.
Other impotence drugs include IC-351, a direct
competitor to Viagra, being developed by Icos Corp. in
Bothell, Wash. The company says the drug, in
early-stage human efficacy testing, appears to be even
more specific to the penis than Viagra and so may be
less likely to affect vision. Viagra produces a temporary
blue-green tinge in the vision of some patients.
Topical gels also were touted as alternatives to Viagra.
Some researchers claimed that MacroChem Corp.'s
experimental Topiglan caused erections just as
frequently as Viagra. But others worried that the gel
could affect women, because it would probably rub off
on them during intercourse if the man wasn't wearing a
condom.
Researchers also said they were experimenting with a
gene treatment that could be injected into the penis
every several months to enhance blood flow. So far the
therapy has produced erections only in laboratory
animals, but if it works in humans "it will be a quantum
leap over anything we have now," said Arnold Melman,
an impotence researcher at Albert Einstein College of
Medicine in New York who is helping to conduct the
research. He cautioned that more animal tests would
have to be completed before human tests can begin.
Separately, impotence doctors at the conference
expressed dismay at recent reports about women
experimenting with Viagra, and strongly advised women
not to do so until studies being sponsored by Pfizer are
completed.
"There are big unanswered questions about the safety
and efficacy of the drug in women," said Dr. Sharlip. In
particular, the San Francisco urologist noted that just
because the drug is safe on men doesn't mean it couldn't
have an adverse effect on a woman's reproductive
system.
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