Melanotan II Research: Mechanism, Studies & Protocols | QSC Peptides
Melanotan II is a research compound studied for its role in cosmetics peptides research. This page covers mechanism of action, published studies, preclinical protocols, and analytical specifications.
Quick Reference: Melanotan II
CAS Number
121062-08-6
Molecular Formula
C50H69N15O9
Molecular Weight
1024.2 g/mol
Sequence / Structure
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH (cyclic lactam analog of α-MSH)
Physical Form
Lyophilized powder
Purity (QSC)
≥99%
Storage
Store lyophilized at -20°C. Reconstituted: 4°C, use within 28 days. Light-sensitive — protect from UV.
Reconstitution
Add 2ml bacteriostatic water per vial. Inject slowly, swirl gently. Protect from light.
Mechanism of Action
Melanotan II (MT-II) is a cyclic lactam analog of alpha-melanocyte-stimulating hormone (α-MSH), itself a melanocortin peptide derived from POMC (pro-opiomelanocortin). MT-II was developed at the University of Arizona as a more potent, metabolically stable analog of α-MSH for research into melanocortin receptor biology.
Broad Melanocortin Receptor Agonism: MT-II is a non-selective melanocortin agonist with high affinity at all five melanocortin receptor subtypes (MC1R–MC5R), distinguishing it from PT-141 (which has relative selectivity for MC3R/MC4R). The receptor distribution and their research implications:
MC1R (Melanocortin 1 Receptor): Expressed on melanocytes in skin and hair follicles. MC1R activation by MT-II stimulates melanogenesis — the production of eumelanin (dark/brown pigment) via cAMP-CREB-MITF signalling cascade. This is the basis for MT-II’s skin tanning research applications.
MC3R and MC4R: Expressed in the CNS, particularly the hypothalamus and limbic system. MC4R activation regulates appetite (POMC/AgRP balance), energy expenditure, and autonomic sexual responses. This CNS activity produces the appetite-suppressing and pro-erectile/pro-lubrication effects documented in MT-II research — the same mechanism exploited by the derived compound PT-141 (bremelanotide).
MC5R: Expressed in exocrine glands. MC5R activation by MT-II influences sebaceous gland secretion and lacrimal gland function — an active area of dry eye and skin condition research.
Research Applications
Melanocortin Receptor Pharmacology: MT-II is the standard broad-spectrum melanocortin agonist used in receptor binding, signalling, and functional assays across all five MC receptor subtypes simultaneously.
Skin Pigmentation Research: MC1R biology is studied using MT-II in melanocyte cell cultures and in vivo mouse models to examine melanogenesis pathway activation, eumelanin vs phaeomelanin production, and UV-protective pigmentation mechanisms.
Appetite Regulation Research: MC4R’s role in hypothalamic energy homeostasis makes MT-II a research tool for appetite suppression and anti-obesity pathway studies — though its broad receptor activity means observed effects require careful attribution between MC subtypes.
Sexual Function Research: MT-II was the parent compound of the PT-141 (bremelanotide) development programme. Research on MT-II’s pro-erectile and pro-lubrication effects in animal models established the CNS melanocortin sexual function mechanism.
Structure-Activity Relationship Studies: Comparison between MT-II (non-selective), PT-141 (MC3R/MC4R selective), and MT-I (MC1R preferring) allows researchers to map specific receptor subtypes to specific biological outcomes — a critical SAR methodology in peptide drug discovery.
Key Published Research
Primary publications relevant to Melanotan II research. Full citations available via PubMed. QSC does not endorse or make claims based on this research.
Comprehensive history of the melanotan development programme, MT-II characterisation, and the downstream PT-141/bremelanotide drug development.
Van der Ploeg et al. (2002)
“Role of Alpha-Melanocyte-Stimulating Hormone MC4 Receptor in Febrile Responses” — PNAS
Establishes MC4R signalling biology relevant to MT-II’s hypothalamic effects, providing mechanistic context for CNS melanocortin research.
Wikberg (2001)
“Melanocortin Receptors: Perspectives for Novel Drugs” — European Journal of Pharmacology
Reviews the MC receptor family pharmacology using MT-II as the reference agonist, establishing the research framework for melanocortin drug development.
Acute single-dose; behavioural endpoints at 30–90 min post-injection; MC4R antagonist controls
Frequently Asked Questions
What is Melanotan II?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of α-MSH (alpha-melanocyte-stimulating hormone). It is a non-selective melanocortin receptor agonist with activity at MC1R (pigmentation), MC3R/MC4R (CNS appetite and sexual function), and MC5R (exocrine glands). It is used in melanocortin receptor pharmacology research.
What is the difference between Melanotan II and PT-141?
PT-141 (bremelanotide) was derived from Melanotan II by removing the C-terminal amide group. PT-141 has modified receptor selectivity — relatively more CNS-selective (MC3R/MC4R) with less peripheral MC1R activity than MT-II. MT-II’s broader receptor profile produces stronger tanning (MC1R) alongside CNS effects; PT-141 focuses on CNS melanocortin pathways.
What is the difference between Melanotan I and Melanotan II?
Melanotan I (afamelanotide) is a linear analog with relative MC1R selectivity and minimal CNS effects. It was developed specifically for skin tanning and photoprotection research. Melanotan II is cyclic with non-selective activity across all MC receptors. Melanotan I has EU approval for erythropoietic protoporphyria; Melanotan II does not.
How should Melanotan II be stored?
Lyophilized at -20°C, protected from UV light. After reconstitution, store at 4°C and use within 28 days. Melanotan II is light-sensitive — minimise exposure to direct light during handling.
What purity is QSC Melanotan II?
≥99% by HPLC and mass spectrometry. COA on product page, Janoshik-verified.
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