PT-141

PT-141, also known as Bremelanotide, is a synthetic cyclic heptapeptide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH) derived from the melanocortin peptide Melanotan II. PT-141 is the active metabolite of Melanotan II that was isolated specifically for its effects on sexual function after clinical trials of Melanotan II unexpectedly revealed potent pro-sexual effects independent of its tanning activity. PT-141 is classified as a melanocortin-4 receptor (MC4R) agonist and is the first peptide to address sexual dysfunction through a central nervous system mechanism rather than a peripheral vascular mechanism (as with PDE5 inhibitors like sildenafil).

PT-141 activates the melanocortin-4 receptor (MC4R) in the hypothalamus, specifically in the medial preoptic area and paraventricular nucleus — brain regions that regulate sexual arousal, desire, and motivation. MC4R activation triggers downstream signaling through the dopaminergic and oxytocinergic pathways that mediate sexual desire and arousal at the neurobehavioral level. This is fundamentally different from PDE5 inhibitors, which increase blood flow to erectile tissue but do not affect desire, arousal, or motivation. PT-141 addresses the "wanting" component of sexual function, not just the mechanical "performing" component.

Clinical trials of PT-141 (branded as Vyleesi) demonstrated statistically significant improvements in sexual desire, arousal, and overall satisfaction in both male and female subjects with hypoactive sexual desire. It received FDA approval in 2019 for premenopausal women with hypoactive sexual desire disorder (HSDD), making it one of the few peptides with full regulatory approval for its primary indication. Research has shown efficacy in both male and female sexual dysfunction, including cases where PDE5 inhibitors were ineffective — confirming its CNS mechanism is complementary to, not redundant with, vascular approaches.

PT-141 is suited for researchers investigating sexual desire and arousal, melanocortin receptor biology, hypothalamic regulation of reproductive behavior, and central mechanisms of sexual function. It is the only peptide compound that addresses the neurological (desire/motivation) rather than vascular (blood flow) component of sexual response.

Reconstitute the 10mg vial with 2ml bacteriostatic water (yielding 5mg/ml). Administer via subcutaneous injection, typically 1-2mg per dose, approximately 45-60 minutes before anticipated research activity. PT-141 has an onset of action of 30-60 minutes and effects lasting 6-12 hours. The half-life is approximately 2.7 hours. Dosing frequency should not exceed once every 24 hours, and most research protocols limit use to 2-3 times per week. The most common side effect is transient nausea, which can be mitigated by starting at lower doses (0.5-1mg). Store at 2-8C after reconstitution.