Overview
PT-141, known by its generic name Bremelanotide, is a synthetic cyclic heptapeptide derived from Melanotan II. It functions as a melanocortin receptor agonist with primary affinity for the melanocortin-4 receptor (MC4R), alongside secondary activity at MC1R and MC3R. Bremelanotide is notable for having achieved genuine medicinal approval: the U.S. Food and Drug Administration approved it in 2019 under the brand name Vyleesi, for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women, administered as a self-injected subcutaneous dose.
It is important to distinguish the regulatory picture for an Irish/EU audience. Vyleesi (bremelanotide) is an FDA-approved medicinal product in the United States for HSDD only. It has not received European Medicines Agency (EMA) approval and is not licensed by the Health Products Regulatory Authority (HPRA) for any indication in Ireland or the wider EU. In an Irish/EU regulatory context, therefore, bremelanotide remains an unlicensed, off-label/research compound rather than an approved medicine — a materially different status from its US approval. This guide addresses PT-141/bremelanotide strictly from a research and educational perspective.
Clinical & Research Status
| Evidence Type |
Status |
| Human RCT |
✔ |
| Observational |
✔ |
| Animal Studies |
✔ |
| In Vitro |
✔ |
| Regulatory Approval |
✔ (FDA, US — Vyleesi, HSDD only. Not EMA/HPRA approved in Ireland/EU.) |
Mechanism of Action
Bremelanotide acts as an agonist at melanocortin receptors, with its therapeutic activity primarily attributed to MC4R activation within the hypothalamus, particularly in and around the paraventricular nucleus. This is a centrally-mediated mechanism, meaning it acts on brain signalling pathways associated with sexual arousal and desire, rather than acting peripherally on vascular tissue. This distinguishes it conceptually from phosphodiesterase type 5 (PDE5) inhibitors such as sildenafil, which work by increasing blood flow at the level of peripheral vasculature and smooth muscle, rather than modulating central arousal circuitry.
Research into the melanocortin system indicates that MC4R activation in the hypothalamus is linked to descending neural pathways implicated in sexual motivation and arousal in both sexes. Because PT-141 acts upstream of the vascular response, its effects have been studied as complementary to, rather than a replacement for, peripherally-acting agents. Its secondary affinity for MC1R also accounts for observed effects on skin pigmentation, a shared characteristic with other melanocortin analogues such as Melanotan II.
Research Areas & Reported Effects
Female Sexual Arousal and Hypoactive Sexual Desire Disorder
The most extensively studied application of bremelanotide is in female HSDD. Palatin Technologies-sponsored Phase 2b and Phase 3 trials, including the pivotal RECONNECT studies, evaluated self-administered subcutaneous bremelanotide in premenopausal women reporting low sexual desire with associated distress. These trials form the basis of the eventual FDA approval of Vyleesi in 2019.
Male Erectile Dysfunction Research (Early Development)
Before Palatin Technologies focused later-stage development on the female HSDD indication, PT-141 was originally investigated for male erectile dysfunction. Early Phase 2 research, including work associated with Diamond LE and colleagues, explored intranasal and subcutaneous bremelanotide as a centrally-acting alternative or adjunct to peripherally-acting PDE5 inhibitors.
Melanocortin System and Appetite/Energy Homeostasis
Because MC4R is a key node in hypothalamic appetite regulation, preclinical research has examined bremelanotide's effects on feeding behaviour and energy homeostasis. This research is largely exploratory and preclinical in nature, reflecting the broader role of the melanocortin system in metabolic regulation rather than a developed clinical indication.
Skin Pigmentation and Cardiovascular Signals
Secondary MC1R activity has been associated with mild pigmentation changes in some research and clinical trial participants, generally to a lesser degree than seen with Melanotan II. Clinical trial data has also consistently flagged transient increases in blood pressure and corresponding decreases in heart rate following dosing, an important safety signal that has been tracked closely across the Vyleesi development programme.
Research Data Summary
| Study / Model |
Reported Effect |
| Palatin Technologies Phase 3 RECONNECT Studies (Kingsberg SA et al.) |
Statistically significant improvements in Female Sexual Function Index (FSFI) desire domain scores and reductions in Female Sexual Distress Scale-Desire/Arousal/Orgasm (FSDS-DAO) scores versus placebo. |
| Clayton AH et al. Phase 2b dose-ranging trial |
Dose-dependent improvement in self-reported sexual desire and reduced associated distress, informing selection of the 1.75 mg dose taken forward to Phase 3. |
| Diamond LE et al. early male ED trial |
Increased rates of erectile response reported in a subset of men with mild-to-moderate erectile dysfunction following intranasal/subcutaneous administration. |
| Safarinejad MR & Hosseini SY 2008 |
Reported improvement in erectile function scores in men with psychogenic erectile dysfunction in a placebo-controlled trial. |
| Cardiovascular safety monitoring (pooled trial data) |
Transient, generally self-limiting increases in blood pressure and decreases in heart rate observed post-dose, monitored closely due to cardiovascular relevance. |
Stack Combinations Studied
- PT-141 + PDE5 inhibitors (e.g. sildenafil, tadalafil) → Research rationale: Investigated conceptually due to complementary mechanisms — PT-141 acts centrally on arousal pathways via MC4R, while PDE5 inhibitors act peripherally on vascular smooth muscle, suggesting a theoretically additive approach studied in some sexual health research contexts.
- PT-141 + Melanotan II → Research rationale: Both are melanocortin receptor agonists derived from related synthesis pathways; research interest has focused on comparing MC1R/MC3R/MC4R selectivity profiles between the two compounds rather than recommending combined use.
- PT-141 + testosterone research protocols → Research rationale: Explored in the context of multifactorial models of low sexual desire, where central melanocortin signalling and gonadal hormone status are both studied as contributing physiological variables.
⚠️ Stack combinations listed for research reference only. Not safety or efficacy guidance.
Research Protocol Reference
experimental research protocols only — not dosing recommendations.
| Protocol |
Dose (experimental model only) |
Duration (experimental model only) |
Frequency (experimental model only) |
Research Context |
| Low-Range Research Protocol |
0.5-1 mg |
Single-dose / short trial |
As needed, prior to activity |
Early dose-finding and tolerability studies. |
| Standard Research Protocol (Vyleesi trial dose) |
1.75 mg |
Up to 8 doses per month studied |
As needed, at least 45 min prior to anticipated activity |
Phase 2b/3 HSDD trials — the approved US dosing regimen for Vyleesi. |
| Historical Male ED Research Protocol |
2-4 mg (intranasal, early studies) |
Single-dose trials |
As needed |
Early Phase 2 erectile dysfunction research prior to indication shift. |
Observed Side Effects in Research
- Nausea (very common; dose-limiting in several trials)
- Flushing
- Headache
- Injection site reactions
- Transient increases in blood pressure and decreases in heart rate
- Skin and gum hyperpigmentation with repeated use (melanocortin-related)
- Vomiting
Nausea and transient blood pressure changes are the most consistently reported findings across the bremelanotide clinical trial programme and are actively monitored in research and clinical settings.
Compound Data
- CAS Number
- 189691-06-3
- Molecular Formula
- C50H68N14O10
- Molecular Weight
- Approximately 1025.2 g/mol
- Half-Life
- Approximately 2.7 hours (subcutaneous administration)
- Synonyms
- Bremelanotide, PT-141, Vyleesi (brand name, US-approved product)
- Research Classification
- Melanocortin receptor agonist (MC4R-selective, cyclic heptapeptide)
Scientific References
- [Clayton AH et al. 2016] — Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. — Women's Health / Journal of Sexual Medicine — [Human RCT]
- [Kingsberg SA et al. 2019] — Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials (RECONNECT). — Obstetrics & Gynecology — [Human RCT]
- [Diamond LE et al. 2004] — An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. — Journal of Sexual Medicine — [Human RCT]
- [Safarinejad MR & Hosseini SY 2008] — Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study. — Journal of Urology — [Human RCT]
- [Molinoff PB et al. 2003] — PT-141: a melanocortin agonist for the treatment of sexual dysfunction. — Annals of the New York Academy of Sciences — [Pharmacology Review]
*This compliance check is automated and does not constitute legal advice. No Nonsense Fitness recommends independent legal review for all published content.*