Melanotan II (MT-II) – Synthetic Cyclic α-MSH Analog & Non-Selective Melanocortin Agonist
Chemical Identity
Chemical Name: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Synonyms: MT-II, Melanotan II
Molecular Formula: C50H69N15O9
Molecular Weight: 1024.2 Da
CAS Number: 121062-08-6
Structure Type: Cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH)
Pharmacological Classification
Melanotan II is a **non-selective melanocortin receptor agonist**, primarily targeting **MC1R**, **MC3R**, **MC4R**, and **MC5R**. It was developed to stimulate melanogenesis, leading to increased skin pigmentation, and has been investigated for its effects on sexual function and appetite regulation.
Mechanism of Action
- MC1R Activation: Stimulates melanocytes to produce eumelanin, resulting in skin darkening.
- MC3R and MC4R Activation: Influences sexual arousal and appetite suppression through central nervous system pathways.
- MC5R Activation: Potentially affects exocrine gland function, though its role is less well-defined.
β-Arrestin Recruitment
As a **G protein-coupled receptor (GPCR)** agonist, Melanotan II's activation of melanocortin receptors may involve β-arrestin-mediated pathways, contributing to receptor desensitization and internalization. However, specific data on β-arrestin recruitment for MT-II is limited.
Melanocortin Receptor Affinity Profile
| Receptor | Affinity | Physiological Role |
|---|---|---|
| MC1R | High | Pigmentation |
| MC3R | Moderate | Energy homeostasis, sexual function |
| MC4R | High | Sexual behavior, appetite regulation |
| MC5R | Low | Exocrine gland function |
Pharmacokinetics
- Administration: Subcutaneous injection
- Bioavailability: High
- Time to Peak Concentration (Tmax): Approximately 1 hour
- Half-Life: Approximately 1.5 hours
- Metabolism: Hepatic
- Excretion: Primarily renal
Biological Effects
Melanotan II has been shown to induce skin tanning through melanogenesis, enhance sexual arousal, and suppress appetite. Side effects may include nausea, flushing, and increased libido. Long-term safety data is limited, and its use is not approved by regulatory agencies for general use.
Stability and Storage
- Form: Lyophilized powder
- Solubility: Water, saline
- Storage: –20°C; protect from light and moisture
- Reconstitution: Use sterile water; avoid repeated freeze-thaw cycles