PT-141, known by its international nonproprietary name Bremelanotide, is a synthetic cyclic heptapeptide melanocortin receptor agonist that acts centrally on MC3R and MC4R receptors in the brain to modulate sexual arousal pathways. Developed originally as a tanning agent from the earlier compound Melanotan II, PT-141 was discovered to produce sexual arousal as an off-target effect during tanning research — an observation that redirected its development toward sexual dysfunction pharmacology. It received FDA approval in 2019 as Vyleesi for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women, providing a regulatory validation that distinguishes it from most research peptides.
For researchers studying the melanocortin system, central versus peripheral mechanisms of sexual function, or the pharmacology of MC3R and MC4R in behavioral neuroscience, PT-141 is a well-characterized tool compound with a defined mechanism, a clinical evidence base, and published pharmacokinetic data across multiple research models.
PT-141 (Bremelanotide) is a cyclic peptide derived from Melanotan II through removal of the C-terminal amide and cyclization of the backbone — structural modifications that reduced the melanogenic (skin-darkening) activity of the parent compound while preserving its central MC3R/MC4R agonism. The cyclic structure confers proteolytic stability and a well-defined three-dimensional receptor-binding conformation.
The melanocortin system — the receptor family that PT-141 acts on — is a network of five receptor subtypes (MC1R through MC5R) with diverse physiological roles. MC1R mediates skin pigmentation; MC2R is the ACTH receptor mediating adrenal cortisol secretion; MC3R and MC4R are expressed in the hypothalamus and limbic system, where they regulate energy balance, sexual function, and behavior; MC5R is expressed in exocrine glands. PT-141’s selectivity for MC3R and MC4R over MC1R and MC2R is the pharmacological basis for its ability to modulate sexual arousal without significant melanogenic or cortisol-stimulating effects at research doses.
| Property | Value |
|---|---|
| Full name | Bremelanotide (PT-141) |
| Also known as | PT-141, Vyleesi |
| Molecular formula | C₅₀H₆₈N₁₄O₁₀ |
| Molecular weight | 1,025.17 g/mol |
| CAS number | 189691-06-3 |
| Purity (Official Peptides) | >99% by HPLC |
| Physical form | White lyophilized powder |
| Solubility | Water soluble |
| Half-life (clinical data) | ~2.7 hours |
| Storage (lyophilized) | 2–8°C, protected from light |
| Storage (reconstituted) | 4°C, use within 30 days |
PT-141’s central mechanism operates through melanocortin 3 and 4 receptors expressed in hypothalamic nuclei — particularly the paraventricular nucleus (PVN) and medial preoptic area (MPOA) — regions with well-established roles in sexual behavior regulation. Research has characterized PT-141’s binding affinities at each melanocortin receptor subtype, establishing its relative selectivity for MC3R and MC4R over MC1R and MC2R and quantifying the receptor activation kinetics underlying its pharmacodynamic profile.
MC4R in particular has received substantial research attention as the receptor mediating PT-141’s pro-sexual effects. Studies using selective MC4R antagonists and MC4R knockout animal models have confirmed that MC4R activation in the hypothalamus is necessary and sufficient for the behavioral effects observed with PT-141 and related melanocortin agonists. Research has also examined MC4R’s role in the integration of sexual arousal signaling with energy balance circuits — MC4R’s dual function in sexual behavior and feeding behavior creates research intersections between sexual function, metabolic state, and hypothalamic signaling.
One of the most pharmacologically significant distinctions between PT-141 and conventional sexual function pharmacology (particularly PDE5 inhibitors such as sildenafil) is the level of the neural hierarchy at which each acts. PDE5 inhibitors act peripherally — in vascular smooth muscle of the corpus cavernosum and equivalent penile/clitoral tissue — to enhance nitric oxide-driven vasodilation and blood flow during sexual arousal. They require that central arousal and the peripheral neurovascular response are both present, and they do not affect desire or arousal at the central level.
PT-141, in contrast, acts in the hypothalamus and limbic system to modulate the central arousal signal itself — the neurological state of sexual desire and motivation — independently of peripheral vascular responses. Research has examined whether this central mechanism allows PT-141 to produce pro-sexual effects in models where PDE5 inhibitors are ineffective, such as in subjects with absent or reduced central arousal signal due to HSDD or in experimental conditions of reduced peripheral blood flow.
Studies examining the interaction between central melanocortin arousal signaling and peripheral vascular responses have characterized how CNS MC4R activation connects to spinal cord erection centers and efferent pathways to genital vasculature. This central-to-peripheral signal transduction involves dopaminergic and oxytocinergic pathways as intermediaries — research has documented that PT-141’s effects on behavior are blocked by dopamine receptor antagonists and that oxytocin release in the PVN is involved in the downstream behavioral response.
The clinical research program that led to PT-141’s FDA approval focused on premenopausal women with HSDD — a condition defined by reduced sexual desire causing personal distress, without another medical or psychiatric cause. The Phase III RECONNECT trials documented that Bremelanotide auto-injected subcutaneously approximately 45 minutes before anticipated sexual activity produced statistically significant improvements in both desire and distressing low sexual desire scores compared to placebo over 24-week treatment periods.
Research examining the RECONNECT trial data has noted that the effect sizes, while statistically significant and clinically meaningful in some subjects, were modest at the population level — a finding that has motivated research into identifying subject subpopulations where MC4R-driven central arousal augmentation produces the largest clinical benefit. Biomarker research examining baseline melanocortin tone, MC4R polymorphisms, and hormonal milieu as predictors of PT-141 response represents an active area of translational investigation.
While PT-141’s clinical approval is in women, research has examined its effects in male sexual dysfunction models with historically encouraging results. Early clinical studies documented PT-141’s ability to produce erections in men with psychogenic and organic erectile dysfunction, including subjects with inadequate responses to PDE5 inhibitors. The mechanism — central MC4R activation driving spinal pro-erectile signaling — operates in males as well as females, and research has examined PT-141 as a potential complement or alternative to PDE5 inhibitor therapy for men in whom the peripheral vascular mechanism is insufficient.
PT-141’s research utility extends beyond sexual function into energy homeostasis, given MC4R’s dual role in regulating both sexual behavior and food intake. MC4R mutations are the most common single-gene cause of monogenic human obesity, and MC4R signaling is a central target in appetite regulation research. Studies examining PT-141 in obesity and energy balance models have helped characterize the overlap and separation of MC4R-mediated sexual and feeding behaviors — research that has implications for the development of more selective melanocortin ligands targeting specific behavioral outputs without cross-effects.
The melanocortin system centers on endogenous ligands derived from the pro-opiomelanocortin (POMC) precursor peptide. POMC-expressing neurons in the arcuate nucleus of the hypothalamus produce α-MSH, β-MSH, and γ-MSH (agonists at MC3R/MC4R) and ACTH (agonist at MC2R/cortisol axis). These are opposed by agouti-related peptide (AgRP)-expressing neurons that produce the endogenous MC3R/MC4R inverse agonist AgRP, creating a push-pull system regulating both energy balance and behavior.
PT-141 enters this system as an exogenous MC3R/MC4R agonist, mimicking the effect of α-MSH at hypothalamic and limbic receptors. Its cyclic structure stabilizes the active binding conformation — the “message” sequence His-D-Phe-Arg-Trp derived from α-MSH’s core pharmacophore — and its higher metabolic stability compared to linear peptides extends its duration of receptor engagement. Receptor activation drives Gs-mediated cAMP increase in MC3R/MC4R-expressing neurons, regulating downstream neurotransmitter release and circuit activity in ways that collectively enhance the motivational and arousal state associated with sexual desire.
Nausea as a research confound: PT-141 produces nausea as a consistent dose-dependent side effect in human research subjects and in rodent models (assessed by pica behavior — consumption of kaolin clay). Research designs examining PT-141 behavioral effects should include nausea monitoring and consider whether nausea independently affects the behavioral endpoints being measured. Lower doses that produce pro-sexual effects without maximal nausea have been characterized in the clinical literature.
Transient blood pressure changes: PT-141 produces transient blood pressure increases in human subjects, attributed to peripheral vascular effects. Research designs examining cardiovascular parameters should include blood pressure monitoring as a standard safety endpoint when using PT-141 at doses above threshold.
Cyclic peptide handling: The cyclic backbone of PT-141 requires standard peptide handling precautions. Reconstitute in bacteriostatic water and store reconstituted solutions at 4°C; use within 30 days. The cyclic structure confers greater proteolytic resistance than linear peptides — PT-141 is relatively stable in serum-containing biological media compared to most linear research peptides.
Official Peptides supplies research-grade PT-141 (Bremelanotide) at >99% purity verified by HPLC and confirmed by mass spectrometry, with batch-specific certificates of analysis available for every purchase. We maintain US-based inventory with cold pack shipping and same-day dispatch on qualifying orders.
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