◆ Sexual Health · Melanocortin Agonist · Cyclic Peptide
PT-141 (Bremelanotide): Melanocortin Agonist Research Summary
A verified research summary of bremelanotide — the cyclic heptapeptide melanocortin-receptor agonist approved by the FDA as Vyleesi, and its regulatory status in Australia.
Silverback Research Team
Independent Literature Review
Compound Data
✓ Research Grade| Compound Name | PT-141 (Bremelanotide) |
| CAS Number | 189691-06-3 (free base) |
| Molecular Weight | 1025.16 g/mol |
| Molecular Formula | C50H68N14O10 |
| Structure | Cyclic heptapeptide: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH |
| Receptor Targets | Melanocortin receptors (MC1R > MC4R > MC3R > MC5R) |
| Elimination Half-life | ~2.7 hours (range 1.9–4.0 h) |
| Developer | Palatin Technologies, Inc. |
| Form (Silverback) | Lyophilised powder, 10mg/vial |
| Purity (Silverback) | ≥99% by HPLC |
| Storage | −20°C sealed · 2–8°C post-reconstitution |
| Regulatory Status | FDA-approved (Vyleesi, 2019) · AU: Schedule 4, unregistered (SAS only) |
Research use only. All information is sourced from published literature for informational purposes. Silverback Peptides products are strictly for laboratory research. Not for human consumption, therapeutic use, or veterinary use.
Overview
Key Takeaways
- PT-141 (bremelanotide) is a synthetic cyclic heptapeptide analogue of α-melanocyte-stimulating hormone (α-MSH).
- It is FDA-approved as Vyleesi (2019) for acquired, generalised hypoactive sexual desire disorder (HSDD) in premenopausal women.
- In Australia it is Schedule 4 but NOT on the ARTG — accessible clinically only via the Special Access Scheme. Silverback supplies it for research only.
PT-141 (bremelanotide) is a synthetic cyclic heptapeptide lactam analogue of endogenous α-melanocyte-stimulating hormone (α-MSH). It is a structured metabolite of melanotan II that lacks the C-terminal amide function, which alters its systemic side-effect profile.
It was developed by Palatin Technologies as a first-in-class melanocortin-receptor agonist targeting central nervous system pathways. It received US FDA marketing approval on 21 June 2019 under the brand name Vyleesi, for acquired, generalised HSDD in premenopausal women.
In Australia, bremelanotide is listed under Schedule 4 (Prescription Only) but is not registered on the Australian Register of Therapeutic Goods. It is an unregistered therapeutic substance, accessible clinically only through the Special Access Scheme (SAS Category B) or specific compounding pathways. Silverback Peptides supplies it for laboratory research only.
Mechanism of Action
Bremelanotide acts as a non-selective agonist of melanocortin receptors, with an activation-potency order of MC1R > MC4R > MC3R > MC5R. Its effect in HSDD is mediated primarily through MC4R activation in the medial preoptic area of the hypothalamus.
Unlike peripheral vasodilators such as PDE5 inhibitors, bremelanotide does not act directly on the vascular system. It crosses the blood-brain barrier to stimulate hypothalamic pathways, triggering dopamine efflux in the nucleus accumbens and medial preoptic area — measured in animal models at 150–200% above baseline — and modulating serotonin pathways involved in sexual motivation.
Key Published Studies
Approval was supported by two identical Phase 3 double-blind, placebo-controlled trials (Study 301 and 302, the RECONNECT trials) in 1,247 premenopausal women with acquired, generalised HSDD over 24 weeks, using 1.75 mg subcutaneously on an as-needed basis. Both co-primary endpoints (desire and distress) reached statistical significance.
“The most common adverse event was nausea, reported by 40% of patients receiving 1.75 mg versus 1.3% on placebo, with a median onset of 30 minutes.”
| Endpoint | Study 301 | Study 302 |
|---|---|---|
| FSFI desire domain (active vs placebo) | +0.32 vs +0.17 | +0.35 vs +0.20 |
| FSDS-R distress score change | −5.7 vs −3.8 | −5.9 vs −3.5 |
| Statistical significance | p < 0.001 | p < 0.001 |
Storage & Handling
Lyophilised bremelanotide should be stored desiccated at −20°C or −80°C. Once reconstituted with sterile 0.9% sodium chloride or sterile water, store at 2–8°C and use within 30 days.
Inspect solutions visually for discoloration or particulate matter before use.