Women suffering from a worrisome decline in their desire for sex — the most common form of female sexual dysfunction — may soon have a new drug to help combat this disorder. A New Jersey-based biopharmaceutical company recently completed Phase 3 clinical trials on a promising peptide drug known as bremelanotide that increases sexual desire and arousal among premenopausal women suffering from these forms of female sexual dysfunction.
Bremelanotide has been developed by Palatin Technologies, which is based in Cranbury, New Jersey. The biopharmaceutical company’s research efforts have been focused on the development of “targeted, receptor-specific peptide therapeutics for the treatment of diseases with significant unmet medical need and commercial potential.”
Addyi Sales Disappointing
In October 2015, Addyi, the first FDA-approved drug designed to increase sexual desire in women suffering from hypoactive sexual desire disorder, or HSDD, came on the market but thus far has failed to generate the sort of sales that were forecast for it. Addyi’s active ingredient is a compound known as flibanserin, which can produce serious adverse side effects. So concerned was the FDA about such side effects that it mandated the inclusion of a black box warning on packaging materials for Addyi.
Unlike Addyi, which must be taken daily to produce positive results, bremelanotide is designed for use as needed. It is an injectable drug that thus far has a better safety profile than Addyi, which can cause extreme dizziness and loss of consciousness and must not be taken by anyone who consumes alcohol.
Satisfying Sexual Events
Both drugs measure their efficacy in terms of the increase in satisfying sexual events (SSEs) that they produce among the female participants in their respective clinical studies. Although Addyi’s backers originally boasted that women taking their drug experienced an increase between 0.5 and 1.0 satisfying sexual event per month, subsequent analyses of the test data placed the actual number of additional SSEs at the low end of that range.
In its clinical tests, bremelanotide produced an average increase of 0.7 SSE among study participants taking the drug, compared with those given a placebo during clinical trials. While these marginal increases in the number of SSEs in women taking Addyi or bremelanotide are not all that different, it should be noted that Addyi must be taken daily to produce and maintain an increase in sexual desire, while bremelanotide is designed for use on demand. Women on Addyi must discontinue all alcohol use, while such a prohibition is not necessary for women taking bremelanotide.
Side Effects Generally Mild
As with most medications, bremelanotide has some side effects, although most are mild and tend to lessen upon continued use of the drug. Nausea, flushing, and headache were the most commonly reported side effects of bremelanotide use. Also reported, but to a lesser extent, were injection-site pain or itching and upper respiratory tract infection.
Among women using Addyi, the most widely reported side effects are dizziness, dry mouth, fatigue, insomnia, nausea, and sleepiness. As mentioned earlier, the drug has also been associated with instances of loss of consciousness. So concerned was the FDA about Addyi’s side effects and interaction with alcohol that it approved the drug under its REMS (Risk Evaluation and Mitigation Strategy) program. Physicians who seek to prescribe the drug and pharmacists interested in dispensing the medication must first take brief online courses designed to familiarize them with the drug’s side effects. These instructional courses are designed to equip both doctors and pharmacists with the knowledge they would need to expertly advise women who are considering taking the drug.
7.4% of Adult Women Affected
According to data supplied by Anita H. Clayton, M.D., lead author on the most recent bremelanotide study, HSDD affects 7.4 percent of all adult women in the United States. However, only about half of those women are premenopausal and thus suitable for treatment with bremelanotide. Dr. Clayton is the chair of psychiatry and neurobehavioral sciences at the University of Virginia Medical School.
Dr. Clayton explained that like Addyi, bremelanotide modifies brain chemistry to increase sexual desire in women whose desire for sex has declined sharply. As explained by Dr. Clayton, the key players in the brain pathways involved in sexual response include both excitatory and inhibitory signals. Among the former, dopamine and melanocortins stimulate attention and desire, while norepinephrine and oxytocin stimulate sexual arousal.
Inhibitory Signals
Among the inhibitory signals are serotonin, opioids, and endocannabinoids. Serotonin regulates satiety, opioids manage sexual rewards, and endocannabinoids play a role in sedation. Bremelanotide rebalances the delicate chemistry within the brain to promote the function of the excitatory signals while temporarily restraining the effects of the inhibitory signals.
Bremelanotide is designed to be injected subcutaneously 45 minutes before the start of sexual activity. In this respect, it is more similar to the male erectile dysfunction drugs, which also are designed to be taken 30 to 60 minutes before the beginning of sexual activity.
As to when bremelanotide might become available to U.S. women suffering from HSDD, Palatin announced in early November 2016 that it hoped to submit a new drug application for the medication to the FDA sometime during the second half of 2017.
Sale or Licensing Deal Sought
According to a report from Reuters on November 2, 2016, Palatin has hired an investment bank to explore the possibilities for a sale or licensing agreement for bremelanotide. According to an anonymous source, Greenhill & Company Inc., a New York-based investment bank, will conduct such a review on Palatin’s behalf to determine the potential for such a sale or licensing deal. The source emphasized that Palatin’s arrangement with Greenhill is no guarantee that this review will result in a deal.
Although clinical tests have shown that bremelanotide’s increase in SSEs is not that much different than those claimed for Addyi, the former’s advantage lies in a purportedly less problematic safety profile. Spokesmen for Palatin believe that their drug can be marketed without the extensive precautionary measures imposed on Addyi, which some have cited as one of the reasons Addyi sales have been slow to take off.
CEO Optimistic
After receiving the latest results on bremelanotide’s efficacy in clinical trials, Carl Spana, Ph.D., president and chief executive officer of Palatin, expressed optimism about the outlook for the drug. “Women with HSDD using bremelanotide had clinically meaningful and statistically significant improvements in their desire and associated distress, which are the defining clinical issues for an HSDD diagnosis.”
Johna D. Lucas, M.D., chief medical officer of Palatin, emphasized that the Phase 3 clinical trials “demonstrated that bremelanotide provided a meaningful benefit for those patients who responded to the drug candidate.” She said that Palatin looks forward to the opportunity to supply “a new and differentiated treatment option to the many women suffering from HSDD.”
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