PT-141 (Bremelanotide): Melanocortin Receptor Agonism and Sexual Function Research
PT-141 (bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist originally developed from Melanotan II. It is the first FDA-approved centrally acting treatment for hypoactive sexual desire disorder — and a key subject in CNS and sexual physiology research.
Dr. Marcus Chen
Senior Research Scientist
PT-141 (bremelanotide; cyclo-[Nle4,Asp5,D-Phe7]-α-MSH(4–10)) is a cyclic heptapeptide and potent agonist of melanocortin receptors MC3R and MC4R. It was derived from Melanotan II — a tanning peptide — after researchers noted its unexpected pro-erectile effect in a human volunteer study. PT-141 was subsequently developed by Palatin Technologies and received FDA approval in 2019 under the brand name Vyleesi® for premenopausal women with hypoactive sexual desire disorder (HSDD).
Mechanism of Action
Unlike PDE5 inhibitors (e.g., sildenafil) which act peripherally on vascular smooth muscle, PT-141 acts centrally in the hypothalamus and limbic system:
- MC3R/MC4R agonism: Activation of melanocortin receptors in the medial preoptic area (MPOA) and nucleus accumbens increases dopaminergic signalling associated with sexual motivation and arousal.
- Melanocortin pathway: PT-141 mimics α-MSH-mediated activation of the hypothalamic melanocortin system, which plays a well-established role in appetite, energy balance, and sexual behaviour.
- Nitric oxide pathway: Secondary effects on peripheral genital blood flow are mediated via neurogenic nitric oxide (nNOS) activation — distinguishing its mechanism from direct vasodilatory agents.
Clinical Research Highlights
PT-141 is one of the few peptides with substantial Phase II/III clinical trial data:
- In RECONNECT trials (Phase III, HSDD in premenopausal women), PT-141 1.75 mg subcutaneous self-administration increased satisfying sexual events (SSEs) by ~0.5 per month versus placebo and significantly improved desire scores.
- Earlier Phase II studies in men with erectile dysfunction (ED) unresponsive to sildenafil showed modest erection improvements, suggesting a complementary CNS mechanism.
- Onset of action is approximately 45 minutes post-administration with effects lasting 6–12 hours.
Researchers studying PT-141 in rodent models or cell lines can source PT-141 research peptide vials from Myotrope, available in 10 mg lyophilised format.
Research Considerations
The nausea and transient blood pressure elevation observed in clinical trials (reported by ~40% and ~15% of subjects, respectively) are attributed to broad melanocortin receptor activation. MC1R effects may also cause transient hyperpigmentation with repeated dosing. These considerations are important in designing animal tolerance studies.
Peptide Profile
| Property | Value |
|---|---|
| Sequence | Cyclo-[Nle4,Asp5,D-Phe7]-α-MSH(4–10) |
| Molecular weight | 1025.2 g/mol |
| FDA approval | June 2019 (HSDD in premenopausal women) |
| Route (approved) | Subcutaneous auto-injector |
| Half-life | ~2.7 hours |
References
- Simon JA, et al. (2019). Efficacy and safety of bremelanotide for premenopausal women with HSDD. Obstetrics & Gynecology, 134(4), 899–908.
- Diamond LE, et al. (2004). PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Annals of the New York Academy of Sciences, 1007, 282–290.
- Molinoff PB, et al. (2003). PT-141: A melanocortin agonist for the treatment of erectile dysfunction. Annals of the New York Academy of Sciences, 994, 96–102.
