Intranasal Melanocortin Receptor Agonist Effective in Erectile Dysfunction

An investigative intranasal melanocortin receptor agonist - PT-141 - is effective for treatment of erectile dysfunction (ED), according to findings presented here May 11th at the 2004 American Urological Association Annual Meeting.

"This treatment is unique because it requires no stimulation for the erection to occur," said Hunter Wessells, MD, Associate Professor of Urology, University of Washington, Seattle, Washington. "It has a different mechanism [of action] than agents like sildenafil, and may become a first-line therapy."

He and his co-investigators were interested in this therapy because melanocortin receptors located in the central nervous system are involved in sexual arousal, Dr. Wessells said. The study drug is a peptide analog of alpha-melanocyte-stimulating hormone that induces erections in both normal men and those with ED (Int J Impot Res. 2004 Feb;16(1):51-9).

In the current study, Dr. Wessells and his team evaluated the safety and efficacy of intranasal PT-141 for the treatment of male ED in the at-home environment.

The study, a multicenter, double blind study with a placebo-control and parallel groups, enrolled 271 men with ED who were responsive to sildenafil. The men had an International Index of Erectile Function (IIEF) erectile function (EF) domain score of 6 to 21 and their average score on this domain was 14.2.

After a 2-week period in which they got no treatment, patients received an intranasal in-clinic dose to assess exposure levels and tolerability. The investigators then randomized the men to PT-141 at a dose of 5 mg, 10 mg, 15 mg or 20mg or to placebo for 10 at-home administrations. The investigators followed patients for a 4-week treatment period, assessing the change in IIEF-EF domain score and patient responses to the General Assessment Questionnaire (GAQ) and the Sexual Encounter Profile (SEP).

Of the 203 patients who completed at least 3 at home attempts, the mean IIEF-EF score increased in a dose-dependent fashion. Functional erections were achieved by 10% of men in the placebo group, 30% of men in the 5 mg group, 36% of men in the 10 mg group, 53% of men in the 15 mg group, and 50% of men in the 20 mg group. Improved erections as documented on the GAQ were reported by 17% of men in the placebo group, 49% of men in the 5 mg group, 67% of men in the 10 mg group, and 66% each in the 15 mg and 20 mg groups.

There were no episodes of syncope or hypotension. There was 1 serious adverse event - a case of prolonged, painless erection that resolved spontaneously. In the 2 highest dose groups, gastrointestinal adverse effects (nausea and vomiting) were the primary reasons for discontinuation and were reported by 12 men as the reason for discontinuation. Others reported some nasal symptoms such as post-nasal drip.

"This at-home study showed PT-141 to be safe and highly effective in inducing high-quality erections in men with ED," said Dr. Wessells.