PT-141 (Bremelanotide)

Bremelanotide, also known as PT-141, is a cyclic synthetic peptide composed of seven amino acids.(1) The synthetic peptide PT-141 appears to be an agonist of melanocortin receptors, similar to the natural hormone alpha-MSH.(2) It is a metabolite of another synthetic analog called Melanotan II. Initial studies suggested that melanocortin hormones primarily affect melanocyte receptors responsible for skin pigmentation. However, further studies in mouse models indicated that a select group induced sexual arousal, leading to the development of Bremelanotide. Cyclic synthetic analogs of alpha-MSH, like PT-141, are potent agonists believed to act on MC3 and MC4 receptors in the central nervous system, thus potentially affecting sexual behavior.(3)

Chemical Composition(4)

• Molecular Formula: C50H68N14O10
• Molecular Weight: 1025.2 g/mol
• Other Titles: Bremelanotide, PT-141
• PubChem ID: 9941379
• CAS Number: 189691-06-3

Early research on alpha-MSH analogs observed unexpected effects on sexual function. Originally intended to study sunless tanning and pigmentation, the administration of Melanotan-II in male test subjects resulted in spontaneous erections. This led to the isolation of the active metabolite, which became PT-141 (Bremelanotide), focusing on its potential aphrodisiac properties.

Research has widely suggested that the PT-141 peptide may act as a potential treatment for sexual dysfunction in both men (erectile dysfunction or impotence) and women (sexual arousal disorder). Studies in male rats showed that systemic administration initiated erection. Unlike other sexual enhancers, research suggests the peptide does not act on the vascular system. Instead, PT-141 might work on the central nervous system (brain) to directly activate dopamine receptors and awaken sexual arousal.(5)

Given that PT-141 is a synthetic analog of the alpha-MSH hormone, it is postulated to interact predominantly with central melanocortin receptors MC3 and MC4. Although alpha-MSH is a non-selective agonist of melanocortin receptors MC1-5, the cyclic structure and properties of PT-141 limit its interactions. Studies in rodents have suggested that PT-141 induces lordosis in females and potentiates erection in males through central actions, specifically in regions of the hypothalamus associated with sexual behavior.(6) This central action contrasts with PDE5 inhibitors (like sildenafil) which primarily act on peripheral vascular mechanisms.

In addition to sexual function, MC4 receptor agonists are implicated in the regulation of food intake and energy balance. Some preclinical studies have observed that the activation of these receptors by analogs like PT-141 could suppress appetite and influence metabolism, although these effects are secondary to its primary investigated impact on sexual function.