- Generic name: Bremelanotide
- Brand name: Vyleesi (FDA approved, HSDD)
- Sequence: Cyclic heptapeptide, melanocortin analogue of Melanotan II
- Molecular weight: 1,025.2 Da · CAS: 189691-06-3
- Targets: MC3R, MC4R (CNS; hypothalamus)
- FDA status: Approved June 2019 (Vyleesi, HSDD in premenopausal women)
01 What Is PT-141?
PT-141, known generically as Bremelanotide and commercially as Vyleesi, is a synthetic cyclic heptapeptide derived from Melanotan II. It is one of the very few research peptides that has progressed all the way through clinical development to FDA approval — a status that lends it a stronger clinical evidence base than almost any other peptide in the research market.
PT-141 was developed by Palatin Technologies after observations that Melanotan II — originally studied for its tanning and UV-protective properties — unexpectedly produced sexual arousal as a side effect in early human trials. Palatin's researchers identified MC3R and MC4R as the relevant receptors, stripped out the tanning activity, and optimised the compound into the cyclic form that became Bremelanotide.
Its mechanism is fundamentally different from all existing treatments for sexual dysfunction: rather than acting on peripheral vascular tissue (PDE5 inhibitors) or on hormonal levels (testosterone supplementation), PT-141 acts centrally in the hypothalamus to modulate the neurological circuits governing sexual desire and arousal.
02 Mechanism of Action
PT-141 activates melanocortin receptors MC3R and MC4R expressed in the paraventricular nucleus (PVN) and medial preoptic area (MPOA) of the hypothalamus — brain regions that are central regulators of sexual behaviour in mammals. MC4R activation in the PVN triggers dopamine release in the mesolimbic pathway, which is the primary neurochemical mediator of sexual motivation and reward.
This mechanism is upstream of both peripheral vascular and hormonal pathways — it essentially activates the desire-initiation circuitry at its neurological source rather than facilitating execution of arousal that has already been initiated. This explains why PT-141 is effective in patients where PDE5 inhibitors and hormone therapy have failed, and why it produces subjective desire (not just physiological response).
MC4R / MC3R
Hypothalamic melanocortin receptor activation in PVN and MPOA
Dopamine Release
Mesolimbic DA pathway activation; mediates sexual motivation and reward
Central Arousal
Acts on desire-initiation circuitry; independent of vascular mechanisms
NO Pathway
Secondary: MC4R-mediated NO signalling supports penile and clitoral engorgement
03 PT-141 vs PDE5 Inhibitors
| Property | PT-141 | Sildenafil / Tadalafil |
|---|---|---|
| Site of action | CNS (hypothalamus) | Peripheral (genital vasculature) |
| Target | MC3R / MC4R | PDE5 enzyme |
| Effect on libido | Yes — central desire | No |
| Works without stimulation | Yes | No — requires arousal |
| Effective in women | Yes (FDA approved) | Limited evidence |
| Cardiovascular interaction | Transient BP increase | BP decrease (nitrate contraindication) |
04 Male Sexual Dysfunction Research
Early human trials of PT-141 in men with erectile dysfunction (ED) — including men who had failed PDE5 inhibitor therapy — showed statistically significant improvements in erectile function scores (IIEF) at doses of 4–20 mg subcutaneous injection. Importantly, the compound produced improvements in sexual desire scores alongside erectile function, consistent with its central mechanism.
A key study in 65 men with psychogenic ED (no organic vascular cause) demonstrated PT-141 produced robust erectile responses in 80% of subjects at 7 mg dose. This psychogenic ED population is specifically poorly-served by PDE5 inhibitors, making PT-141's central mechanism particularly relevant.
05 Female Sexual Dysfunction & FDA Approval
The FDA approval pathway for PT-141 focused on hypoactive sexual desire disorder (HSDD) in premenopausal women — a condition affecting approximately 10% of women and characterised by persistently low sexual desire causing distress. Unlike male ED, HSDD has no effective peripheral treatment because desire cannot be mechanically facilitated; it requires central neurological intervention.
Phase III trials (RECONNECT studies, n=1,267) in premenopausal women with HSDD showed Bremelanotide (1.75 mg SC auto-injector) significantly increased the number of satisfying sexual events per month and reduced FSDS-DAO (Female Sexual Distress Scale) scores compared to placebo, leading to FDA approval in June 2019.
06 Clinical Trials Summary
- Phase I: Safety in healthy volunteers — well-tolerated; transient nausea and blood pressure elevation noted
- Phase II (male ED): Significant IIEF improvements including PDE5-failure patients
- Phase III RECONNECT (female HSDD): n=1,267; statistically significant endpoints → FDA approval June 2019
- Post-approval: Vyleesi (1.75 mg/0.3 mL auto-injector) available by prescription in USA for premenopausal HSDD
07 Safety Profile
The most common adverse effect is nausea (40% of subjects in Phase III), which is dose-dependent and transient (typically resolving within 2 hours). Facial flushing and transient systolic blood pressure increases of 6–10 mmHg were also reported. PT-141 is contraindicated with cardiovascular disease due to the blood pressure effect. The FDA label recommends not using more than once every 24 hours and no more than once per 8 weeks in clinical use.
No effects on sex hormone levels, gonadotropins, or cortisol were observed in chronic dosing studies. The compound has a clean organ safety profile in preclinical toxicology.
08 Protocol Notes (Preclinical)
- Rodent sexual behaviour studies: 0.1–1 mg/kg SC; endpoints measured at 30–90 min post-injection
- Phase II human dose range: 4–20 mg SC (clinical doses; not for non-clinical research)
- Approved clinical dose: 1.75 mg SC auto-injector (Vyleesi)
Reconstitute lyophilised powder in bacteriostatic water. Store at −20°C. Cyclic peptide structure is relatively stable; avoid strongly acidic or alkaline buffers.
09 FAQ
What is PT-141?
PT-141 (Bremelanotide/Vyleesi) is an FDA-approved cyclic melanocortin peptide that activates MC3R/MC4R in the hypothalamus to modulate central sexual arousal. Approved for HSDD in premenopausal women.
Is PT-141 FDA approved?
Yes — as Vyleesi (1.75 mg SC) for HSDD in premenopausal women, approved June 2019. One of very few peptides with full FDA approval.
How does PT-141 differ from PDE5 inhibitors?
PDE5 inhibitors work peripherally on vascular tissue and require prior arousal. PT-141 acts centrally in the hypothalamus to generate sexual desire, making it effective independently of peripheral vascular function and in women.
PT-141 — Lyophilised Research Powder
≥98% purity · Endotoxin tested · COA included · Ships within 24 h