Bremelanotide

Bremelanotide (formerly PT-141) is the generic term for a new medication for use in treating sexual dysfunction in men (erectile dysfunction or impotence) as well as sexual dysfunction in women (sexual arousal disorder). It is the only known synthetic aphrodisiac. Unlike Viagra and other related medications, it does not act upon the vascular system, but directly increases sexual desire. Bremelanotide is a spray introduced nasally.

Development
Originally, the peptide Melanotan II that bremelanotide was developed from was tested as a sunless tanning agent. In initial testing, Melanotan II did induce tanning but additionally caused sexual arousal and spontaneous erections as unexpected side effects in nine out of the ten original male volunteer test subjects. In clinical studies, bremelanotide has been shown to be effective in treating male sexual and erectile dysfunction as well as female sexual dysfunction. It is currently being tested by Palatin Technologies.

A Phase III clinical trial was scheduled to begin in the first half of 2007, but was delayed until August 2007. On August 30th, Palatin announced that the FDA had expressed serious concerns regarding the benefit/risk ratio of bremelanotide  with regards to the side effect of increased blood pressure. The FDA also stated that they would consider alternate uses for bremelanotide, including as a treatment for individuals who do not respond to more established ED treatments.

Structure
Bremelanotide is a cyclic hepta-peptide lactam analog of alpha-melanocyte-stimulating hormone (alpha-MSH) that activates the melanocortin receptors MC3-R and MC4-R in the central nervous system. It has the amino acid sequence Ac-Nle-cyclo[Asp-His- D -Phe-Arg-Trp-Lys]-OH or cyclo-[Nle4, Asp5, D -Phe7, Lys10]alpha-MSH-(4-10). PT-141 is a metabolite of Melanotan II that lacks the C-terminal amide function. Its molecular formula is C50H68N14O10 with a molecular weight of 1025.2.