Peptide Research
PT-141 (Bremelanotide) Research: Melanocortin Receptor Pathways
⚠ FOR LABORATORY RESEARCH AND EDUCATIONAL PURPOSES ONLY — NOT FOR HUMAN OR ANIMAL CONSUMPTION.
Quick answer: PT-141 (bremelanotide) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that acts as a melanocortin receptor agonist, with research focus on the MC3R and MC4R subtypes expressed in hypothalamic and limbic tissue. Because it engages central rather than peripheral pathways, researchers use it as a tool compound for probing melanocortin signalling. It is supplied strictly as a research material.
Molecular Profile
- Name: PT-141 (bremelanotide)
- CAS Number: 189691-06-3
- Type: Synthetic cyclic heptapeptide (α-MSH analogue)
- Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH
- Molecular formula: C₅₀H₆₈N₁₄O₁₀
- Molecular weight: approximately 1025.2 g/mol
- Form: Lyophilized powder for reconstitution
The Melanocortin Receptor System
The melanocortin system comprises five G-protein-coupled receptor subtypes, each with distinct tissue distribution:
| Receptor | Primary Distribution | Research Association |
|---|---|---|
| MC1R | Melanocytes, immune cells | Melanogenesis, inflammatory signalling |
| MC2R | Adrenal cortex | Steroidogenesis (ACTH receptor) |
| MC3R | Hypothalamus, limbic system | Energy homeostasis, reward-related signalling |
| MC4R | Hypothalamic nuclei | Autonomic outflow, neuroendocrine regulation |
| MC5R | Exocrine tissue | Sebaceous and exocrine function |
In binding assays, PT-141 demonstrates activity across MC1R, MC3R, MC4R, and MC5R.1 However, published research concentrates on MC3R and MC4R, since these subtypes are most densely expressed in central nervous tissue.2
Why PT-141 Is Used as a Research Tool Compound
Two properties account for its position in the literature. First, PT-141 crosses the blood-brain barrier, which distinguishes it from many peripherally acting peptides. Second, its mechanism is centrally mediated rather than vascular — a distinction that has made it useful for investigators separating central neural pathways from peripheral mechanisms in comparative study designs.3
When bremelanotide binds MC4R, published work describes a Gs-protein-coupled cascade producing downstream cAMP accumulation, which is why cAMP quantification appears frequently as a readout in in-vitro melanocortin assays.4
Note on study design: the literature commonly recommends including a melanocortin antagonist control such as SHU-9119 when attributing observed effects specifically to MC4R activation.
Relationship to Melanotan-2
PT-141 originated from α-MSH analogue research conducted at the University of Arizona in the 1980s under Mac Hadley and Victor Hruby.5 Structurally, PT-141 is a metabolite of Melanotan-2, formed through hydrolysis of the MT-2 lactam bridge.
Consequently, researchers at Palatin Technologies characterised PT-141 as a more selective derivative: reduced activity at peripheral MC1R (the subtype associated with melanogenesis) while retaining central MC3R and MC4R engagement. For that reason, the two compounds are frequently examined in parallel to identify which structural features drive receptor subtype selectivity.
Published Research Findings
- Receptor pharmacology: binding and functional assays have characterised subtype selectivity across the melanocortin family1,2
- Preclinical models: MC4R agonism has been associated with autonomic and behavioural endpoints in rodent and primate studies6
- Genetic validation: loss-of-function models provided direct evidence identifying MC4R as the mediating receptor target7
- Clinical development: bremelanotide progressed through Phase 3 trials (the RECONNECT programme, reported 2019), which supported an approved pharmaceutical formulation8
Regulatory Status
This point requires explicit statement. The bremelanotide molecule exists in an FDA-approved prescription pharmaceutical formulation, approved in 2019 for a specific clinical indication. The research-grade PT-141 discussed here is not that product. It is a laboratory research material, not manufactured or approved for pharmaceutical or clinical use, not a substitute for any prescription medication, and not intended for human or animal administration. No comparison to any approved pharmaceutical product is made or implied.
Handling and Storage
- Store lyophilized vials refrigerated at 2–8°C, protected from light and heat; longer-term storage at −20°C is common practice
- Reconstitute with bacteriostatic water; reconstituted material has a considerably shorter storage window
- Cyclic peptides are sensitive to repeated freeze-thaw cycling — aliquot accordingly
- Follow your laboratory’s standard handling and disposal protocol
Why Purity Matters in Melanocortin Research
Receptor-binding studies depend on precise sequence identity, because closely related melanocortin analogues produce measurably different subtype selectivity profiles — the very distinction between PT-141 and Melanotan-2 illustrates the point. Additionally, residual endotoxin can activate inflammatory signalling that overlaps with MC1R pathways, confounding results.
For these reasons, laboratories require documented HPLC purity, mass-spectrometry identity confirmation, and LAL endotoxin testing. LiveWell manufactures its research peptides in our own cGMP facility in Dallas, Texas — we are the manufacturer, not a reseller — and publishes batch-specific documentation on our COA page rather than supplying it on request only.
Frequently Asked Questions
What is PT-141?
PT-141, systematically named bremelanotide, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone. CAS 189691-06-3, molecular weight approximately 1025.2 g/mol. In research contexts it functions as a melanocortin receptor agonist and is supplied as a lyophilized powder for laboratory use only.
Which melanocortin receptors does PT-141 engage?
Binding assays report activity at MC1R, MC3R, MC4R, and MC5R. Published research concentrates on MC3R and MC4R, the subtypes most densely expressed in hypothalamic and limbic tissue, with MC4R identified as the primary mediating target in preclinical models.
How does PT-141 differ from Melanotan-2?
PT-141 is a metabolite of Melanotan-2, formed by hydrolysis of the MT-2 lactam bridge. It shows reduced activity at peripheral MC1R while retaining central MC3R and MC4R engagement, which is why the two are often studied in parallel to map structure-selectivity relationships.
Is PT-141 an approved medication?
The bremelanotide molecule exists in an FDA-approved prescription formulation approved in 2019 for a specific clinical indication. Research-grade PT-141 is a separate laboratory material — not manufactured or approved for pharmaceutical use, and not a substitute for any prescription medication.
What controls are recommended in MC4R studies?
The literature commonly recommends a melanocortin antagonist control such as SHU-9119 when attributing observed effects specifically to MC4R activation, alongside cAMP quantification as a functional readout in in-vitro assays.
How should PT-141 be stored for research use?
Store lyophilized material refrigerated at 2–8°C protected from light, or at −20°C for longer-term storage. Reconstitute with bacteriostatic water and aliquot to minimise freeze-thaw cycling, since cyclic peptides are sensitive to repeated cycling.
Related Research
Research compounds: KPV (α-MSH fragment) · All research vials · Certificates of Analysis
Continue the series: Sleep and Stress Peptide Research · Mitochondrial Peptides in Research · Antimicrobial Peptides in Research
External context: PubMed
References
- Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones. Peptides. 2006;27(4):921–930.
- Gantz I, Fong TM. The melanocortin system. Am J Physiol Endocrinol Metab. 2003;284(3):E468–E474.
- Molinoff PB, et al. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96–102.
- Yang Y, et al. Molecular determinants of ligand binding at melanocortin receptors. Biochemistry. 2000;39(48):14900–14911.
- Hruby VJ, et al. Cyclic lactam α-melanotropin analogues. J Med Chem. 1995;38(18):3454–3461.
- King SH, et al. Melanocortin receptor agonists and central pathways in preclinical models. Peptides. 2007;28(12):2490–2497.
- Van der Ploeg LH, et al. A role for the melanocortin 4 receptor in sexual function. PNAS. 2002;99(17):11381–11386.
- Kingsberg SA, et al. Bremelanotide for hypoactive sexual desire disorder: two randomized Phase 3 trials. Obstet Gynecol. 2019;134(5):899–908.
For research and educational purposes only. This article summarises published literature as a scientific reference for qualified researchers. It does not describe effects in humans, is not medical or health advice, and contains no dosing guidance. Research-grade material is not a drug, is not approved for pharmaceutical use, and is not a substitute for any prescription medication. All LiveWell products are supplied strictly for in-vitro laboratory research and are not for human or animal consumption.