Self-Administered Injection Boosts Low Sex Drive in Women

Fran Lowry

May 30, 2013

HOLLYWOOD, Florida — Subcutaneous injections of the melanocortin receptor agonist bremelanotide effectively and safely treat premenopausal women suffering from female sexual dysfunction, new research shows.

Self-administered at home, right before sex, both 1.25-mg and 1.75-mg SC doses decreased distress, increased arousal and desire, and enhanced the women's enjoyment of sex, lead researcher Anita H. Clayton, MD, David C. Wilson Professor in the Department of Psychiatric Medicine at the University of Virginia Health System, Charlottesville, told Medscape Medical News.

The study was presented here at the New Clinical Drug Evaluation Unit (NCDEU) 53rd Annual Meeting.

Enhances Dopamine

"Female sexual dysfunctions, including hypoactive sexual desire or low sexual desire that causes distress, and female sexual arousal disorder are common, and currently there are no approved drug therapies for these conditions," said Dr. Clayton.

"The women in this study have a primary sexual disorder, and women who have sexual dysfunction because they are depressed or on antidepressant therapy were excluded from the trial," she said.

As a melanocortin receptor agonist, bremelanotide enhances dopamine, which excites or enhances sexual functioning, Dr. Clayton explained.

The current study included 327 women with hypoactive sexual desire or female sexual arousal disorder, or both, for at least 6 months, as diagnosed by a qualified clinician. All the women were in a stable relationship and were willing to be sexually active at least once a month.

All women received a placebo dose in the clinic and then self-injected with placebo for the following 4 weeks. They were then randomly assigned in a double-blind fashion to placebo or bremelanotide 0.75, 1.25, or 1.75 mg, which was given at 2 clinic visits a week apart. This was followed by 12 weeks of at-home subcutaneous injections.

The syringes were prefilled, and the women were instructed to self-inject 45 minutes prior to sexual activity and to use only 1 dose per day and no more than 16 doses during a 4-week period.

The main outcome was the number of satisfying sexual events.

"A lot of women with low sexual desire will participate in sexual activity anyway because their partner wants it or out of obligation, but they are not interested or into it," said Dr. Clayton.

"They still could get aroused and even have an orgasm, but they still might not feel that connectedness or feel satisfied with the whole outcome. That is why we wanted to use this satisfying sexual events, or SSE, measure, which looks at how many times the woman had sex and how many times it was satisfying," she added.

Well Tolerated

The study also looked at changes in the Female Sexual Function Index (FSFI) and the Female Sexual Distress Scale–Desire/Arousal/Orgasm (FSDS-DAO).

Treatment with bremelanotide resulted in improvement in all 3 outcome measures, with the 1.75-mg dose resulting in the greatest improvements, Dr. Clayton said.

Dr. Anita Clayton

For women randomly assigned to placebo, the mean (standard deviation [SD]) increase in SSEs was 0.2 (2.3) and 0.6 (3.6) for the 0.75-mg dose (P = .4430).

In keeping with the linear dose response curve, women who were randomly assigned to bremelanotide 1.25 mg showed a mean increase in SSEs of 0.7 (1.8, P = .0807 vs placebo), and those who received the 1.75-mg dose showed a mean increase in SSEs of 0.8 (2.9, P = .0215 vs placebo).

The FFSI score similarly increased with bremelanotide.

The mean change in FSFI total score was 1.88 (5.92) for placebo vs 2.75 (5.70) for 1.25-mg (P = .279) and 4.36 (5.58) for the 1.75-mg dose (P = .0021).

Distress about sexual function also decreased. The mean change in the FSDS-DAO total score was -6.8 (13.6) with placebo, vs -9.2 (10.8) for 1.25 mg (P = .0508) and -13.1 (12.9) for 1.75 mg (P = .0005).

The drug was "very well tolerated," Dr. Clayton said.

"We looked at blood pressure very intensely because there used to be an intranasal product that seemed to have some erratic absorption and therefore elevated blood pressures. But this is now a subcutaneous injection on demand, and it does not look as if there will be any issues about this going forward."

Nausea was the most common side effect, but this occurred early after the injection, was mild, and stopped with continued use. Other side effects were flushing and headache.

Phase 3 trials are currently planned, Dr. Clayton said.

A "Deal Breaker"

R. Michael Allen, MD, a psychiatrist at the Richfield Institute, New Smyrna, Georgia, provided independent comment on the study for Medscape Medical News.

"It's great that they are studying this. Sexual dysfunction is a big problem among my patients who are depressed or who are on medication for depression," he said.

"It's true that they excluded women who have sexual dysfunction from depression or antidepressant therapy from this study, which was a dose-ranging study, but the fact that it shows some efficacy in the women who have primary sexual disorder is very encouraging and hopefully will be useful in cases where the sexual dysfunction is medication induced.

"A lot of people say to just live with the side effect of sexual dysfunction, because it's better than being depressed, but for many of my patients, it's a deal breaker. They get better from their depression and now can't enjoy sex. They've lost a very important part of their life," Dr. Allen said.

This study was funded by Palatin Technologies Inc. Dr. Clayton reports financial relationships with Palatin Technologies Inc., Ballantine Books/Random House, Changes in Sexual Functioning Questionnaire, Guilford Publications, BioSante Pharmaceuticals, Inc., Euthymics Bioscience, Forest Research Institute, Inc., Lundbeck, Inc., Pfizer Inc, S1 Biopharma, Sprout Pharmaceuticals, Takeda Global Research & Development, and Trimel Pharmaceuticals. Dr. Allen reports no relevant financial relationships.

New Clinical Drug Evaluation Unit 53rd Annual Meeting. Abstract 90. Presented May 29, 2013.

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