// Compound Reference · Melanocortin Receptor Agonist

PT-141

Bremelanotide · CAS 189691-06-3 · MW 1025.2 g/mol · Cyclic Heptapeptide

A synthetic cyclic heptapeptide derived from the C-terminal hydroxyl variant of Melanotan II. PT-141 acts as a selective agonist at central melanocortin receptors — principally MC3-R and MC4-R — and is studied for its role in neuroendocrine signalling, autonomic arousal pathways, and CNS-mediated physiological responses independent of gonadal hormone activity.

MC3-R / MC4-R Agonist
≥99.2% HPLC Purity
Cyclic Heptapeptide
5 mg / vial
CoA Included
Cold Shipped

Purity

≥99.2%

Molecular Weight

1025.2 g/mol

Structure

Cyclic, 7 AA

Testing Lab

Freedom Diagnostics

01 Mechanism of Action

PT-141 (bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist. Its primary pharmacological distinction lies in its CNS-centric activity profile: rather than acting peripherally through vascular or hormonal pathways, PT-141 engages melanocortin receptors within the hypothalamus and limbic system to influence autonomic and neuroendocrine output.

The compound binds selectively to MC3-R and MC4-R subtypes, both densely expressed in hypothalamic nuclei involved in energy balance, autonomic tone, and reward circuitry. MC4-R activation in the paraventricular nucleus and medial amygdala has been linked to modulation of dopaminergic projections and downstream physiological arousal responses.

Structurally, PT-141 is the des-hydroxyl metabolite of Melanotan II — it retains the cyclic lactam bridge (Asp–Lys) but carries a free C-terminal hydroxyl group rather than an amide, conferring slightly altered receptor selectivity and metabolic stability.

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Research Note: PT-141’s CNS-mediated mechanism is pharmacologically distinct from PDE5 inhibitors and hormonal therapies. It does not directly modulate cGMP pathways or systemic sex hormone levels, making it a useful research tool for isolating central melanocortin contributions to autonomic arousal physiology.

02 Research Applications

CNS Melanocortin Signalling

PT-141 is a well-characterised pharmacological tool for probing MC3-R and MC4-R function in hypothalamic circuits. Researchers have used it to examine the role of central melanocortin tone in autonomic arousal, dopamine release dynamics, and the interaction between melanocortin and opioid receptor systems.

Hypoactive Sexual Desire Research

Phase 3 data (RECONNECT trials) demonstrated statistically significant improvements in satisfying sexual events and desire scores versus placebo. This research pathway led to FDA approval of the 1.75 mg subcutaneous formulation (Vyleesi) in 2019.

Trial	Population	Duration	Primary Endpoint	Outcome
RECONNECT-1	Premenopausal women, HSDD	24 weeks	eDiary SSE count	Significant improvement vs placebo
RECONNECT-2	Premenopausal women, HSDD	24 weeks	FSDS-DAO desire subscale	Significant improvement vs placebo
Phase 2 (NCT00463086)	Mixed, HSDD / ED	12 weeks	Sexual response endpoints	Dose-dependent responses observed

PT-141 vs. Melanotan II — Structural Comparison

// Bremelanotide

PT-141

C-terminus–OH (free acid)

Primary ReceptorsMC3-R, MC4-R

PigmentationMinimal

CNS SelectivityHigh

MW1025.2 g/mol

// α-MSH Analog

Melanotan II

C-terminus–NH₂ (amide)

Primary ReceptorsMC1-R through MC5-R

PigmentationPronounced (MC1-R)

CNS SelectivityModerate

MW1024.2 g/mol

03 Observed Research Effects

Nausea (most frequent, ~40%)

Flushing / facial warmth

Headache

Vomiting

Transient blood pressure elevation

Transient heart rate decrease

Fatigue / somnolence

Injection-site reactions

Nasal congestion

Dizziness / lightheadedness

Signals Requiring Monitoring

Transient hypertension — Clinically meaningful blood pressure elevations observed in a subset of trial participants. Self-limiting but warrants baseline cardiovascular characterisation.
Hyperpigmentation — Focal darkening of skin reported with repeated administration. Attributable to off-target MC1-R activity on melanocytes and may be irreversible with prolonged exposure.
Bradycardia — Transient slowing of heart rate post-injection, likely via autonomic reflex.
Drug absorption interactions — PT-141 slows gastrointestinal transit, potentially delaying absorption of orally administered co-compounds.
Reproductive toxicity (preclinical) — Animal studies identified embryofetal developmental concerns at supratherapeutic doses.

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Research Use Only. Peplix supplies PT-141 exclusively for in-vitro laboratory and preclinical research. This data does not constitute medical guidance.

04 Contraindication Profile

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Clinical Contraindications (Vyleesi prescribing data): Known cardiovascular disease; uncontrolled hypertension; concurrent use of naltrexone; pregnancy (embryofetal toxicity in animal studies); and use in postmenopausal women (indication not established).

These contraindications provide useful pharmacological framing for researchers designing studies involving PT-141.

05 Chemical & Physical Profile

Full NameBremelanotide (PT-141)

CAS Number189691-06-3

Molecular Weight1025.2 g/mol

StructureCyclic heptapeptide, lactam bridge Asp³–Lys⁷

SequenceAc-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH

Key ModificationsN-terminal Nle; D-Phe at position 4; cyclic lactam; C-terminal –OH

Parent CompoundMelanotan II (C-terminal amide variant)

Half-life~2.7 hours (subcutaneous)

Physical FormLyophilized white powder

SolubilitySoluble in bacteriostatic water or sterile saline (~1 mg/mL)

Storage−20°C (lyophilized); 2–8°C reconstituted; protect from light

Peplix Purity≥99.2% by HPLC

Testing LabFreedom Diagnostics

Lot Number2603

06 Reconstitution Reference

BAC Water Added	Concentration	Vol per 500 µg	Doses / Vial
1.0 mL	5,000 µg/mL	100 µL	10
2.0 mL	2,500 µg/mL	200 µL	10
5.0 mL	1,000 µg/mL	500 µL	10

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Protocol Note: PT-141 is a cyclic peptide with good aqueous solubility. Reconstitute by injecting bacteriostatic water slowly along the vial wall and swirling gently. Use the Reconstitution Calculator for precise volumes.

07 Research Literature

Simon JA et al. Efficacy and Safety of Bremelanotide for Hypoactive Sexual Desire Disorder. Obstet Gynecol. 2019;134(5):899–908.

Clayton AH et al. Bremelanotide for Female Sexual Dysfunctions in Premenopausal Women. Obstet Gynecol. 2016;128(6):1160–1164.

Safarinejad MR. Evaluation of Bremelanotide in Male Patients with Erectile Dysfunction. J Urol. 2008;179(3):1104–1108.

Pfaus JG et al. The Neurobiological Underpinning of Erotic Motivation by Melanocortins. Psychopharmacology. 2010;213(1):129–143.

Molinoff PB et al. PT-141: A Melanocortin Agonist for the Treatment of Sexual Dysfunction. Ann N Y Acad Sci. 2003;994:96–102.

Order PT-141 · 5 mg Vial

≥99.2% HPLC purity · CoA from Freedom Diagnostics · Cold shipped · Lot 2603

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