A cyclic heptapeptide derived from alpha-MSH that activates melanocortin receptors in the hypothalamus and limbic system - the first compound ever approved that targets sexual desire through brain pathways rather than peripheral vascular mechanisms.
Compound characterisation data. For Research Use Only. Not the FDA-approved drug Vyleesi®.
Manufactured in US
US-formulated & filled
Endotoxin Tested
<0.05 EU/mL verified
Independently Tested
Freedom Diagnostic · 6-panel COA
Same Day Shipping
Order by 3PM PST
Found while
studying
tanning.
PT-141 wasn’t designed to target sexual desire. It emerged from research into skin pigmentation - specifically from studies of Melanotan II, a melanocortin agonist being investigated for tanning. Researchers noticed an unexpected side effect: sexual arousal. That serendipitous observation led Palatin Technologies to engineer a cleaner derivative, eventually yielding the first FDA-approved drug targeting desire through brain pathways.
1990s
Melanotan II - Tanning Research
Researchers studying melanocortin agonists for skin pigmentation notice an unexpected side effect: spontaneous sexual arousal in study participants. The compound lacked specificity and caused significant nausea.
2000
PT-141 Synthesized - Palatin Technologies
Palatin Technologies engineers a cyclic heptapeptide derived from Melanotan II by removing the C-terminal amide. This eliminates the potent tanning effect while preserving and refining the sexual response activity. PT-141 = cleaner, more selective.
2004–2008
Formulation Change
Early formulation work moved away from the nasal route following blood-pressure findings, and the development programme was redirected toward a different indication.
June 2019
Vyleesi® Approved as a Pharmaceutical
Bremelanotide was approved under the brand name Vyleesi® as a finished pharmaceutical. That approval covers the licensed medicine only, and does not extend to this research material.
Every established sexual health compound before PT-141 worked peripherally - dilating blood vessels, increasing blood flow to genital tissue. PT-141 is mechanistically different: it operates centrally, in the hypothalamus and limbic system, activating the neural circuits that generate desire itself. This distinction is why it works in PDE5 inhibitor-resistant populations and why it addresses desire (not just physical response).
The FDA prescribing information notes that the exact mechanism by which Vyleesi improves HSDD is not fully characterized - an honest acknowledgment that MC4R agonism’s downstream pathway to desire is complex. What is established: MC4R knockout mice show markedly impaired sexual function, and MC4R is concentrated in hypothalamic and limbic regions governing arousal and motivation.
Mechanism Comparison
PT-141 activates melanocortin-3 and melanocortin-4 receptors in the hypothalamus and limbic system. MC4R is a Gαs-coupled GPCR - receptor binding raises intracellular cAMP, which activates downstream signaling cascades that influence dopaminergic neurotransmission and nitric oxide release. The downstream pathway from MC4R to desire involves neural circuits in the hypothalamic preoptic area, nucleus accumbens, and amygdala.
MC3R / MC4R Binding → Gαs Activation
PT-141 binds MC3R and MC4R in the hypothalamus and limbic regions. MC4R is highly expressed in the hypothalamic preoptic area and paraventricular nucleus - both established regulators of sexual behavior. Ki = 10 nM at human MC4R (competitive binding against NDP-α-MSH in HEK-293 cells). MC4R couples to Gαs protein.
cAMP Accumulation → PKA → Downstream Cascades
Gαs activation → adenylate cyclase → ↑cAMP → PKA. PT-141 induces cAMP accumulation in hMC4R-expressing HEK-293 cells (documented pharmacological assay endpoint). Parallel activation of phospholipase C → IP3/DAG → Ca2+ also documented for MC3R.
Dopamine Release → Reward Circuit Activation
MC4R activation in hypothalamic circuits enhances dopaminergic neurotransmission - the same reward circuitry underlying motivation and desire. Dopamine pathway activation in the nucleus accumbens and mesolimbic system generates the subjective experience of wanting/desire. NO (nitric oxide) release also documented as a downstream mediator.
Limbic System Activation → Sexual Arousal & Desire
Neural signal propagation through amygdala, nucleus accumbens, and cortex generates desire and arousal independent of genital stimulation or vascular events. In rodent models, PT-141 has been studied for arousal-related behaviours through activation of neurons in brain regions associated with sexual function.
Research Endpoint Areas
Hypoactive Sexual Desire Disorder - Female Models
MC4R agonism in female models is an area of ongoing research interest. FSDS-DAO and FSFI are standard validated instruments used in this research domain.
Erectile Dysfunction - Including PDE5-Resistant
MC4R agonism is studied as a central pathway distinct from the peripheral vascular mechanism of PDE5 inhibitors. Research interest centres on models where the vascular route is not the limiting fDE5-resistant population (Safarinejad & Hosseini 2008). IIEF and nocturnal penile tumescence are standard endpoints.
Melanocortin Receptor Pharmacology - CNS Biology
PT-141 is the primary research tool for MC4R pharmacology studies. cAMP HTRF assay in MC4R-expressing HEK-293 cells. Receptor binding competition assays against NDP-α-MSH. MC4R knockout phenotype comparison. Behavioral paradigms in rodent models.
SSRI-Induced Sexual Dysfunction Models
PT-141 is studied in models of SSRI-induced sexual dysfunction - a common adverse effect of antidepressants that operates through serotonergic suppression of MC4R signaling. Research into melanocortin system modulation as a reversal mechanism for iatrogenic sexual dysfunction.
Molecular and analytical data from Eon Peptides batch records.
Long-term
-20°C
Lyophilized sealed. Stable 24 months. Avoid frost-free freezers.
Short-term
2–8°C
Sealed and desiccated. Appropriate for near-term holding.
Solubility
Water-soluble
Soluble in water and in PBS at pH 7.0–7.4.
Avoid
Oxidants
Protect from light. Cyclic peptide backbone is sensitive to oxidative degradation.
For Research Use Only - Not for Human Consumption. Not Vyleesi® or any approved drug. Supplied exclusively for in vitro laboratory research by qualified researchers.
| Common Name | PT-141 / Bremelanotide |
| Brand Name | Vyleesi® (bremelanotide injection) - FDA-approved drug. Not Eon Peptides’ product. |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH |
| CAS Number | 189691-06-3 |
| Molecular Formula | C50H68N14O10 |
| Molecular Weight | 1,025.16 Da |
| Structure | Cyclic heptapeptide · lactam ring · N-terminal acetylated norleucine · D-Phe pharmacophore |
| Primary Targets | MC3R, MC4R (melanocortin receptors) - hypothalamus and limbic system |
| Receptor Affinity | MC4R Ki = 10 nM (HEK-293 competitive binding vs NDP-α-MSH) |
| Signaling | MC4R → Gαs → ↑cAMP → PKA → dopamine → arousal circuits |
| PK Peak (Tmax) | ~1 hr reported for the licensed pharmaceutical |
| Plasma t½ | 2.7 hr (range 1.9–4.0 hr) |
| Bioavailability | ~100% reported for the licensed pharmaceutical |
| Form | Lyophilized powder · sealed glass vial |
| Purity | ≥99% HPLC · Mass Spec verified · 6-panel COA · Freedom Diagnostic |
| Endotoxin | <0.05 EU/mL · LAL-tested · Freedom Diagnostic |
| Regulatory | RUONot Vyleesi® - In Vitro Research Use Only |