New Inhaled Impotence Drug Shows Promise

Backers Say PT-141 Is Effective and Safe

From the WebMD Archives

Nov. 6, 2003 - A new type of erectile dysfunction drug that is delivered by nasal spray shows promise in early clinical trials. Instead of directly affecting blood vessels in the penis as the currently available drugs do, the novel treatment targets the brain -- specifically, the region of the brain that regulates sexual response.

In a Thursday morning news conference, officials with New Jersey manufacturer Palatin Technologies Inc. said they plan to study the treatment in men who either don't respond to or cannot take Viagra or similarly acting drugs for erectile dysfunction. They also plan to test it for sexual dysfunction in women and are searching for a corporate partner to help them develop and market the drug, now known as PT-141.

Few Side Effects at Low Doses

More trials of the drug in men with erectile dysfunction are scheduled for completion late in 2006, and the company hopes to win FDA approval within the following year. If that happens, PT-141 could be the first drug approved for erectile dysfunction that acts on the central nervous system.

Another central nervous system-acting drug, Uprima, was slated to become the first real competitor to Viagra until its manufacturer withdrew its application for FDA approval in the summer of 2000. According to news accounts, one in 30 men who took the optimal dosage of Uprima fainted or suffered severe low blood pressure as a result.

Urologist and impotence researcher Harin Padma-Nathan, MD, who led trials for both Uprima and PT-141, says low blood pressure was not seen as a side effect in the 271 men taking part in the newly reported PT-141 trial.

"It was very clear that (PT-141) was very different from any other centrally acting agent," he said Thursday.

He added that side effects with the lowest doses of PT-141 were very similar to what has been seen with Viagra, Levitra, and another drug expected to win approval for the treatment of erectile dysfunction called Cialis. All three drugs work by increasing blood flow to the penis, creating an erection.

PT-141 is in a new class of drugs that works on the part of the brain involved in sexual function.

GI Problems Seen at Higher Doses

The men in the PT-141 trial who took the highest doses of the drug did have an unacceptably high incidence of gastrointestinal side effects, including nausea. They made up almost all of the roughly 12% of patients who dropped out of the trial, and one researcher says future studies will not include these higher doses.

Those included in the trial had mild to severe erectile dysfunction, and all had taken Viagra prior to enrollment and had responded well to it. The men took PT-141 via nose sprays at least three times, and some took it as many as 10 times before reporting improved erections.

One in 10 men who received placebo treatments reported restoration of normal erectile function, compared with roughly one in three patients treated with the lowest dosage of PT-141 and one in two patients treated with the highest dosage.

Palatin Technologies CEO Carl Spana, PhD, said men taking part in future studies will be started off at the lowest dosage and dosages will be increased gradually, if needed, to minimize side effects.

The company is also planning drug interaction studies evaluating the safety of PT-141 in men using nitrate medications for heart disease. Viagra and similar drugs are not recommended for these patients, and Spana says they account for roughly 10% of men with erectile dysfunction.

"We have no reason to expect that PT-141 will interact with nitrates," he says. "This represents a significant potential advantage."

San Francisco urologist Ira Sharlip, MD, who researches new impotence treatments but was not involved with the PT-141 study, tells WebMD that it is too soon to know whether the new drug will end up being an important new treatment.

"Right now in the United States we have Viagra and Levitra, and I expect that Cialis will soon be available," he says. "These are good drugs, but they aren't perfect. They don't work for everybody, so having a drug that works by a completely different mechanism of action is an attractive prospect."

Show Sources

SOURCES: Palatin Technologies Inc. news conference. Carl Spana, PhD, president and CEO, Palatin Technologies, Cranbury, N.J. Perry Molinoff, MD, former Palatin executive vice president of research and development; vice provost for research, University of Pennsylvania. Harin Padma-Nathan, MD, clinical professor of urology, University of Southern California; director, The Male Clinic, Beverly Hills, Calif. Ira Sharlip, MD, spokesman, American Urological Association; private practice, San Francisco.
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