PT-141 For Lab Research

PT-141 Peptide | Buy PT-141 UK | Research Use Only

PT-141 — also known as Bremelanotide and Vyleesi (FDA-approved pharmaceutical formulation) — is a synthetic cyclic heptapeptide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, MW 1,025.2 Da) originally derived as an active metabolite of Melanotan II and engineered as a non-selective melanocortin receptor agonist with highest affinity for MC4R, acting centrally in the medial preoptic area and paraventricular nucleus of the hypothalamus to modulate dopaminergic, noradrenergic, and serotoninergic neurotransmission governing sexual desire and arousal — making it the only CNS-acting melanocortin system research tool with a full Phase II and Phase III clinical evidence base, FDA approval (2019) as Vyleesi for hypoactive sexual desire disorder in premenopausal women, and a pharmacological profile mechanistically distinct from PDE5 inhibitors — operating upstream on the neural circuitry of desire rather than downstream on vascular nitric oxide pathways. Buy PT-141 in the UK from Peptides Lab UK with >99% HPLC-verified purity, batch-specific COA, and fast UK dispatch for laboratory and in vitro research use only.

Distributed by Peptides Lab UK in lyophilised format for controlled laboratory research. Each batch is independently verified for purity. This compound is handled strictly in pre-clinical settings and is distinct from the licensed pharmaceutical formulation Vyleesi.

What Is PT-141?

PT-141 (Bremelanotide) is a synthetic cyclic heptapeptide melanocortin receptor agonist first synthesised in 2000 as an active metabolite and structural refinement of Melanotan II — itself a synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH) originally developed as a sunless tanning agent. Early clinical studies with Melanotan II unexpectedly identified potent pro-sexual and pro-erectile effects in male volunteers — effects mediated centrally through the melanocortin system rather than through peripheral vascular mechanisms — which prompted the development of PT-141 as a purpose-designed, more selective CNS melanocortin agonist optimised for sexual behaviour research and clinical application.

PT-141’s cyclic heptapeptide structure — incorporating a D-Phe residue at position 4 and a cyclised structure via an Asp-Lys lactam bridge — confers greater receptor binding stability and metabolic resistance than linear melanocortin peptides, while its chemical modification relative to α-MSH shifts selectivity away from MC1R (peripheral pigmentation) toward central MC3R and MC4R, the receptors most relevant to sexual behaviour circuitry.

In 2019, the US FDA approved bremelanotide subcutaneous injection (Vyleesi, AMAG Pharmaceuticals) for the treatment of acquired, generalised hypoactive sexual desire disorder (HSDD) in premenopausal women — making it only the second approved pharmacotherapy for female sexual dysfunction and the first melanocortin-based medicine to reach clinical approval. The research-grade PT-141 supplied by Peptides Lab UK is a distinct non-pharmaceutical material.

Also Known As

• Bremelanotide
• Vyleesi (AMAG Pharmaceuticals — US FDA approved pharmaceutical, 2019)
• Melanotan II metabolite / PT-141
• Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH
• CAS No. 189691-06-3

PT-141 vs Melanotan II — Critical Research Distinction

PT-141 is frequently confused with Melanotan II in lay and research literature. The two compounds are related but pharmacologically distinct:

Property	PT-141 (Bremelanotide)	Melanotan II (MT-II)
Structure	Cyclic heptapeptide — lactam bridge Asp-Lys	Linear cyclic — disulphide bridge
MC1R Activity	Lower — less pigmentation effect	Higher — significant tanning effect
MC4R Selectivity	Higher — more CNS-focused	Lower — broader MCR activation
Pressor Activity	Mild transient	More pronounced
Pro-sexual Research	Primary research application	Incidental discovery (tanning agent)
FDA Approval	Yes — Vyleesi (HSDD, 2019)	No
Research Use	Melanocortin CNS biology, sexual function, MC4R pharmacology	Pigmentation, MC1R biology, broad melanocortin

How Does PT-141 Work?

Melanocortin Receptor Pharmacology — MCR Binding Profile

PT-141 is a non-selective melanocortin receptor agonist with affinity across the MCR family in the following order of potency: MC1R > MC4R > MC3R > MC5R > MC2R. At therapeutically and research-relevant doses, MC4R is the primary pharmacologically active receptor — both because it has the highest CNS expression density in regions governing sexual behaviour and because MC1R-mediated pigmentation effects (the basis of the tanning response to MT-II) are substantially attenuated in PT-141’s cyclic structure.

The melanocortin receptors are Gs-coupled GPCRs — receptor engagement activates adenylyl cyclase, increases intracellular cAMP, and drives PKA-mediated downstream signalling. In MC4R-expressing hypothalamic neurons, this signalling cascade modulates neurotransmitter release patterns governing sexual desire, arousal, and the psycho-physiological sexual response cycle.

MC4R — The Primary Target in Sexual Behaviour Circuitry

MC4R is expressed at highest density in the medial preoptic area (mPOA) of the hypothalamus — a region universally recognised as a master regulatory centre for sexual motivation and behaviour across mammalian species. Activation of presynaptic MC4Rs in the mPOA by PT-141 is proposed to increase dopamine release — a mechanistic model consistent with the role of dopaminergic neurotransmission in sexual motivation, reward anticipation, and arousal initiation. MC4R activation also modulates noradrenergic and serotoninergic neurotransmission, reflecting the multi-neurotransmitter landscape of hypothalamic sexual behaviour regulation.

This CNS-mediated pro-sexual mechanism is mechanistically upstream of, and independent from, the nitric oxide/cGMP/PDE5 pathway targeted by sildenafil (Viagra), tadalafil (Cialis), and other PDE5 inhibitors — which act at the vascular/penile smooth muscle level as downstream effectors of a pre-existing arousal signal. PT-141 does not require pre-existing arousal to initiate its effects; it acts at the level of desire generation itself.

Paraventricular Nucleus Activation — c-Fos Neuronal Mapping

Systemic administration of PT-141 in rats activates neurons in the paraventricular nucleus (PVN) of the hypothalamus, demonstrated by increased c-Fos immunoreactivity — the standard molecular marker of acute neuronal activation. Notably, pseudorabies virus studies have confirmed that neurons in the same PVN region that PT-141 activates are trans-synaptically connected to the corpus cavernosum — directly linking PT-141’s hypothalamic activation to the neural pathways governing penile erection. This anatomical connectivity provides mechanistic support for PT-141’s ability to generate erections without requiring peripheral sexual stimulation.

Oxytocin and Dopamine Release — Reward Pathway Integration

PT-141’s activation of hypothalamic MC4R circuits includes stimulation of oxytocin-releasing neurons in the PVN — providing a mechanistic basis for affective dimensions of PT-141’s pro-sexual effects beyond simple arousal, including enhanced bonding, intimacy experience, and positive hedonic valence. Dopamine release in the medial preoptic area and nucleus accumbens integrates the PT-141 signal into the brain’s reward and motivation circuits — explaining observations that PT-141’s effects include qualitative sexual desire enhancement and motivational approach behaviour rather than simply facilitating a physical response.

Melanocortin System Context — Excitatory/Inhibitory Balance

Current neuroendocrinological models of female sexual desire characterise the brain’s sexual response system as a balance between excitatory (dopamine, norepinephrine, oxytocin, melanocortins) and inhibitory (serotonin, opioids, prolactin, endocannabinoids) neurotransmitter pathways. HSDD — the condition for which Vyleesi is FDA-approved — is conceptualised as an imbalance toward excessive inhibition relative to excitation. PT-141 acts specifically on the excitatory arm of this system via melanocortinergic activation, providing the mechanistic rationale for its research application in models of central sexual desire dysregulation.

Peripheral Contributions — MC3R and Nitric Oxide

Beyond the central MC4R mechanism, MC3R activation and possible peripheral melanocortin receptor engagement may contribute to PT-141’s effects through nitric oxide-related mechanisms in peripheral sexual tissue — complementing rather than duplicating the central mechanism. Some literature describes PT-141-mediated nitric oxide release as a secondary pathway contributing to smooth muscle relaxation in erectile tissue — but this is considered a downstream consequence of central neural activation rather than a primary mechanism.

What Does PT-141 Do in Research?

In laboratory and pre-clinical settings, PT-141 (Bremelanotide) is studied as the defining CNS melanocortin agonist for sexual behaviour neuroscience and melanocortin receptor pharmacology:

• MC4R pharmacology — receptor binding kinetics, Gs/cAMP/PKA signalling, hypothalamic expression mapping, and MC4R-selective research design
• Melanocortin receptor profiling — MC1R/MC3R/MC4R/MC5R binding affinity, SAR studies, and MCR subtype selectivity research
• Central sexual behaviour neuroscience — mPOA and PVN neuronal activation, c-Fos immunoreactivity, and hypothalamic circuit mapping
• Dopamine system modulation — mPOA dopamine release, nucleus accumbens reward integration, and monoaminergic neurotransmitter crosstalk
• Oxytocin circuit activation — PVN oxytocin neuron stimulation and affective/bonding dimension of sexual response
• HSDD research models — female sexual desire deficiency models, melanocortin excitatory pathway engagement, and excitation/inhibition balance
• Erectile dysfunction research — MC4R-mediated erectile pathway, PVN-corpus cavernosum neural connectivity, and PDE5-independent erection modelling
• CNS vs peripheral mechanism dissection — central melanocortin pathway vs nitric oxide/PDE5 axis; independent and additive mechanism studies
• Sildenafil-resistant erectile dysfunction — MC4R agonism as an alternative mechanism in PDE5-nonresponsive research models
• Female sexual arousal disorder (FSAD) — vaginal vasocongestion, subjective arousal, and genital sensory response research models
• Melanotan II comparative pharmacology — MC1R vs MC4R selectivity, structural modification effects, and pro-sexual vs tanning activity dissection
• Melanocortin system neuroendocrinology — α-MSH/β-MSH/γ-MSH comparative binding, ACTH-melanocortin crosstalk, and hypothalamic regulation
• Energy homeostasis and appetite research — MC3R/MC4R’s dual role in sexual function and feeding behaviour; obesity-sexual function crosstalk
• Pigmentation research — residual MC1R activity of PT-141 relative to MT-II; focal hyperpigmentation as pharmacodynamic biomarker
• Transient hypertension mechanism — pressor activity, cardiovascular monitoring research, and dose-dependent blood pressure profiling
• Melanocortin peptide drug design — cyclic vs linear α-MSH analogues, lactam bridge effects, SAR for MC4R selectivity improvement
• Vyleesi pharmacokinetics — Tmax 1 hour, Cmax 72.8 ng/mL, AUC 276 hr·ng/mL, urinary excretion 64.8%, faecal research applications 22.8%

What Do Studies Say About PT-141?

The Original Erectile Activity Study — Molinoff et al. 2003

The landmark 2003 study by Molinoff, Shadiack, Earle, Diamond, and Quon published in Annals of the New York Academy of Sciences confirmed that PT-141 administration to normal men and patients with erectile dysfunction produced a rapid, dose-dependent increase in erectile activity — establishing the foundational clinical pharmacodynamic data for PT-141’s erectile research application and confirming that the CNS melanocortin pathway generates erectile responses independently of peripheral vascular mechanisms.

Subcutaneous PT-141 in Men — Rosen et al. 2004

The pivotal study by Rosen, Diamond, Earle et al. published in the International Journal of Impotence Research evaluated subcutaneous PT-141 (0.3–10 mg) in healthy male subjects and in men with inadequate Viagra response. The study confirmed dose-dependent improvement in erectile activity using RigiScan monitoring, established the subcutaneous route as the most appropriate delivery form for controlled dosing, and documented the pressor activity profile — a transient blood pressure increase — that informed subsequent dose refinement and the nasal spray formulation’s eventual discontinuation in clinical development.

Female Sexual Arousal Disorder — Diamond et al. 2006

The 2006 randomised, double-blind, placebo-controlled study by Diamond, Earle, Heiman, Rosen, Perelman, and Swabb published in the Journal of Sexual Medicine evaluated intranasal PT-141 in 18 premenopausal women with primary female sexual arousal disorder. Significantly more women reported moderate or high sexual desire following bremelanotide vs placebo (p = 0.0114), and among women attempting intercourse within 24 hours of treatment, significantly more reported satisfaction with their level of sexual arousal following bremelanotide vs placebo (p = 0.0256) — providing the foundational female sexual dysfunction dataset that directed PT-141 toward HSDD clinical development.

Phase IIb Dose-Finding — Clayton et al. 2016

The Phase IIb randomised, placebo-controlled dose-finding trial by Clayton, Althof, Kingsberg et al. published in Women’s Health evaluated bremelanotide across three doses (0.75 mg, 1.25 mg, 1.75 mg) in premenopausal women with HSDD. All active doses produced statistically significant improvements in satisfying sexual events, Female Sexual Function Index desire domain scores, and Female Sexual Distress Scale scores compared to placebo — establishing the dose-response data that determined the final 1.75 mg dose selected for Phase III pivotal trials and FDA submission.

Phase III RECONNECT Trials — FDA Approval Dataset

The Phase III RECONNECT trials (RECONNECT-1 and RECONNECT-2) — a pair of randomised, double-blind, placebo-controlled, multicentre studies — enrolled approximately 1,247 premenopausal women with HSDD across North America and confirmed statistically significant improvements in the number of satisfying sexual events and reduction in distress from low sexual desire with bremelanotide 1.75 mg subcutaneous vs placebo. This Phase III dataset formed the primary evidence basis for the FDA’s June 2019 approval of Vyleesi — making PT-141/bremelanotide the first and only approved melanocortin-based medicine in human clinical use.

Sildenafil-Resistant ED — Safarinejad and Hosseini 2008

The 2008 placebo-controlled crossover study by Safarinejad and Hosseini evaluated PT-141 in 180 men with sildenafil-resistant erectile dysfunction. The PT-141 group demonstrated 62% improvement in erectile function vs 21% in the placebo group (p < 0.001) — directly establishing PT-141’s utility as a mechanistically distinct alternative for PDE5-nonresponsive research models, and confirming that the CNS melanocortin pathway is not downstream of or dependent on the nitric oxide/PDE5 axis.

Key Cited Studies

• Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY (2003) — PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci 994:96–102. DOI: 10.1111/j.1749-6632.2003.tb03167.x. PMID: 12851303
• Rosen RC, Diamond LE, Earle DC et al. (2004) — Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res 16(2):135–142. DOI: 10.1038/sj.ijir.3901200. PMID: 14963477
• Diamond LE, Earle DC, Heiman JR, Rosen RC, Perelman MA, Swabb E (2006) — An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med 3(4):628–638. DOI: 10.1111/j.1743-6109.2006.00268.x. PMID: 16839319
• Clayton AH, Althof SE, Kingsberg S et al. (2016) — Bremelanotide for female sexual dysfunctions in premenopausal women: a randomised, placebo-controlled dose-finding trial. Womens Health 12(3):325–337. DOI: 10.2217/whe-2016-0001. PMC5066811
• Simon JA, Kingsberg SA, Portman D et al. (2019) — Long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder. Obstet Gynecol 134(5):909–917. DOI: 10.1097/AOG.0000000000003514. PMID: 31568259
• Safarinejad MR & Hosseini SY (2008) — Salvage of sildenafil failures with bremelanotide: a randomised, double-blind, placebo controlled study. J Urol 179(3):1066–1071. DOI: 10.1016/j.juro.2007.10.063. PMID: 18206921
• Kingsberg SA, Clayton AH, Portman D et al. (2019) — Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomised Phase 3 trials. Obstet Gynecol 134(5):899–908. DOI: 10.1097/AOG.0000000000003500. PMID: 31568257

PT-141 vs Other Sexual Function and Melanocortin Research Compounds

Feature	PT-141 (Bremelanotide)	Melanotan II (MT-II)	Sildenafil (PDE5i — reference)	Kisspeptin-10
Compound Type	Cyclic synthetic heptapeptide	Cyclic synthetic α-MSH analogue	Small molecule phosphodiesterase-5 inhibitor	Kisspeptin fragment — neuropeptide
Primary Target	MC4R (CNS — mPOA/PVN)	MC1R > MC4R > MC3R (broader)	PDE5 (penile smooth muscle)	Kiss1R on GnRH neurons
Site of Action	Central — hypothalamus, limbic system	Central and peripheral — broader	Peripheral — penile smooth muscle/vasculature	Central — hypothalamic GnRH neuron
Mechanism	MC4R-mediated dopamine/oxytocin release; desire initiation	Broad melanocortin activation; pigmentation + pro-sexual	cGMP preservation; smooth muscle relaxation; NO pathway	GnRH pulse stimulation; LH/FSH release; indirect pro-sexual
FDA Approval	Yes — Vyleesi (HSDD, premenopausal women, 2019)	No	Yes — multiple indications (ED)	No
Pro-Sexual Evidence	Extensive — Phase II and III clinical trials	Pre-clinical and early clinical (penile erections)	Extensive — global clinical data	Emerging — human and rodent studies
Sexual Desire (Libido)	Yes — primary mechanism	Yes — incidental finding	No — arousal/erection only	Yes — upstream HPG axis
Erection Without Stimulation	Yes — c-Fos PVN activation	Yes	No — requires arousal signal	Indirect via LH/testosterone
Female Sexual Dysfunction	Yes — HSDD, FSAD clinical data	Limited	Not indicated	Limited
Pigmentation Effect	Mild (reduced vs MT-II)	Significant (primary original target)	None	None
Pressor Activity	Transient mild blood pressure increase	More pronounced	Mild hypotension (vasodilation)	None
Half-Life	~1–2 hours	~1–2 hours	4–5 hours (sildenafil)	~10–28 minutes
Research Use	MC4R pharmacology, CNS sexual behaviour, dopamine/oxytocin circuits	Broad MCR pharmacology, pigmentation	PDE5 pathway reference compound	HPG axis, reproductive neuroendocrinology

Quality & Purity Assurance

Every batch of PT-141 from Peptides Lab UK is:

• >99% pure — HPLC and mass spectrometry verified
• Supplied with a full Certificate of Analysis (COA) on request
• Lyophilised powder for maximum stability and long shelf life
• Manufactured under strict, controlled laboratory conditions
• Consistent batch-to-batch quality for reproducible research results

Buy PT-141 UK — Product Specifications

Property	Detail
Full Name	PT-141 / Bremelanotide
Also Known As	Vyleesi (pharmaceutical), Melanotan II metabolite, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH
Sequence	Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH
Structure	Cyclic heptapeptide — lactam bridge (Asp-Lys)
Amino Acids	7 (cyclic heptapeptide)
Molecular Weight	1,025.2 Da
Molecular Formula	C₅₀H₆₈N₁₄O₁₀
CAS Number	189691-06-3
MCR Potency Order	MC1R > MC4R > MC3R > MC5R > MC2R
Primary Research Target	MC4R (medial preoptic area / paraventricular nucleus)
Half-Life	~1–2 hours
Tmax (SC)	1.0 hour (0.5–1.0 h)
Bioavailability (SC)	~100%
Purity	>99% (HPLC verified)
Form	Lyophilised powder
Storage	Store dry at -20°C; protect from light
Solubility	Sterile water or bacteriostatic water; well-soluble

PT-141 Research Applications

PT-141 (Bremelanotide) UK is supplied strictly for the following in vitro and pre-clinical research uses:

• MC4R binding kinetics, Gs/cAMP/PKA signalling, and hypothalamic MCR expression mapping
• Melanocortin receptor subtype selectivity research — MC1R/MC3R/MC4R/MC5R affinity profiling
• Central sexual behaviour neuroscience — mPOA/PVN circuit mapping, c-Fos neuronal activation, and corpus cavernosum connectivity
• Dopaminergic neurotransmission — mPOA dopamine release, nucleus accumbens reward integration
• Oxytocin system activation — PVN oxytocin neuron stimulation and affective sexual response dimensions
• HSDD pre-clinical models — melanocortin excitatory pathway, excitation/inhibition balance research
• Erectile dysfunction research — PVN-corpus cavernosum neural pathway, PDE5-independent erection models
• CNS vs peripheral mechanism dissection — melanocortin/central vs NO/PDE5/peripheral axis
• Sildenafil-resistant ED research models — MC4R agonism as alternative mechanism
• Female sexual arousal and desire disorder models — subjective arousal and genital response research
• Melanotan II comparative pharmacology — cyclic peptide modification effects on MCR selectivity
• Melanocortin system neuroendocrinology — α-MSH, ACTH crosstalk, and hypothalamic regulation
• Energy homeostasis and appetite — MC4R dual role in sexual function and feeding behaviour
• Pigmentation biology — MC1R residual activity, focal hyperpigmentation as pharmacodynamic biomarker
• Melanocortin peptide drug design — SAR for MC4R selectivity; cyclic vs linear α-MSH analogue comparison
• PT-141 pharmacokinetics — Tmax, Cmax, AUC, urinary excretion profiling

Why Buy PT-141 UK from Peptides Lab UK?

Peptides Lab UK is a trusted UK peptides supplier providing research-grade compounds verified by independent HPLC testing. When you buy PT-141 in the UK from us, you receive:

99% purity, HPLC and MS verified, third-party tested

• Full COA documentation per batch
• Fast same-day UK dispatch with tracked delivery
• Competitive pricing with bulk research discounts available
• Trusted by researchers across the UK and Europe

Research Disclaimer

All products supplied by Peptides Lab UK are intended strictly for in vitro laboratory research and scientific study use only. They are not intended for human consumption, veterinary use, or any medical or therapeutic application. The research-grade lyophilised PT-141 (Bremelanotide) supplied by Peptides Lab UK is not a pharmaceutical product and is distinct from the FDA-approved pharmaceutical Vyleesi (bremelanotide injection, AMAG Pharmaceuticals) approved for HSDD in premenopausal women. PT-141 is not approved by the MHRA for any therapeutic indication in the UK. Researchers should note that PT-141 produces a transient, dose-dependent increase in blood pressure — it must not be used by individuals with cardiovascular disease, uncontrolled hypertension, or high cardiovascular risk, and must not be self-administered or used outside a controlled laboratory environment. All citations on this page refer to published pre-clinical and peer-reviewed clinical research and do not constitute a claim of safety or therapeutic efficacy for the research compound supplied herein. Peptides Lab UK accepts no liability for any misuse of research compounds. By purchasing, you confirm that you are a qualified researcher and that the product will be used solely within a controlled laboratory environment in compliance with all applicable UK laws, regulations, and institutional guidelines.