What is Melanotan II?
Melanotan II is a cyclic seven-residue analogue built from the α-MSH signalling region. An aspartate–lysine side-chain lactam bridge constrains the chain, while norleucine and D-phenylalanine further distinguish it from the native hormone. The ring changes how the receptor-facing residues are presented; it is not simply a shortened version of linear Melanotan I.
Early structure–activity experiments found that ring size and the assay species changed biological potency. Small human studies later recorded pigmentation and erectile responses, alongside nausea and other systemic observations. These responses underline the breadth of melanocortin biology rather than demonstrating a narrowly selective action. The clinical samples were extremely small, so receptor and structure experiments remain important for understanding the molecule without treating early pilot findings as a settled safety or efficacy profile.
Related scientific guides: Melanotan I and II: structural differences.
Melanotan II Research Areas
Increased pigmentation was recorded in two of three men in an early Melanotan II pilot, alongside nausea, fatigue, yawning and spontaneous erections. The breadth of responses is consistent with a compound acting across melanocortin biology. Three participants are far too few to establish a dependable efficacy or safety profile.
Dorr et al. · Life Sci · 1996PubMed
Melanotan II produced clinically apparent erections in eight of ten men in a placebo-controlled crossover experiment, with longer periods of high tip rigidity. Nausea, yawning, stretching and reduced appetite were more frequent after the peptide. The six-hour recordings provide a specific physiological observation in a small selected group, with little information about longer-term outcomes.
Wessells et al. · J Urol · 1998PubMed
Molecular profile
- Compound
- Melanotan II
- Amount
- 10 mg
- Sequence
- Ac-Nle-cyclo[Asp-
His-D-Phe- Arg-Trp-Lys]-NH2 - Residue count
- 7
- Molecular formula
- C50H69N15O9
- Molecular weight
- 1024.2 g/mol
- CAS number
- 121062-08-6
- Chemical class
- Synthetic cyclic alpha-melanocyte-stimulating hormone analogue
- Classification
- Research peptide
- Parent molecule
- Melanotan II
- Available vial sizes
- 10 mg
Analytical verification
- Lynx report reference
- UKLY-850
- Reported purity
- 99.759%
- Analysis method
- RP-HPLC + ESI-MS
- Identity result
- Confirmed: Melanotan II
- Analysis date
- 4 Sept 2026
- Report date
- 4 Sept 2026
Storage & Reconstitution
Store in appropriate cool, dry conditions. Refer to product-specific storage information when published.
Vials are supplied separately from bacteriostatic water and other preparation supplies.
For laboratory handling context, read Research peptide storage and stability. Product-specific information and the laboratory method take precedence.
For laboratory preparation, allow the sealed vial to reach room temperature before opening. Wipe the vial stopper and bacteriostatic-water stopper with an alcohol wipe. Add bacteriostatic water slowly down the inside wall of the vial, then swirl gently until dissolved. Do not shake.
Research literature
- Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Dorr et al. · Life Sci · 1996PubMed
- Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study.Wessells et al. · J Urol · 1998PubMed
Melanotan II Price (UK)
Melanotan II is supplied in 10 mg vials for laboratory research. The current price is £24.99.
Current availability is shown below. UK orders of £49.99 or more qualify for free standard shipping. Eligible working-day orders placed before 4 PM are dispatched the same day.
| Vial size | Current price | Price / mg | Status |
|---|---|---|---|
| 10 mg | £24.99 | £2.50/mg | Checking stock |
Common questions about Melanotan II
What is Melanotan II?
Melanotan II is a synthetic, cyclic alpha-MSH analogue containing seven amino acids. It is studied at several melanocortin receptor subtypes, including MC1, MC3, MC4 and MC5. Its compact ring-shaped design distinguishes it from the longer, linear Melanotan I, giving researchers a different molecular structure for comparing receptor binding and cellular responses.
How does Melanotan II differ from Melanotan I?
Melanotan II is a shorter, cyclic alpha-MSH analogue, while Melanotan I has a linear 13-amino-acid chain. The different shapes and substitutions change how they interact with melanocortin receptors. Melanotan II is studied across MC1, MC3, MC4 and MC5, while Melanotan I is closely associated with MC1-related pigmentation research; results depend on the receptor and assay being compared.
Why is Melanotan II described as cyclic?
A bond between aspartate and lysine side chains closes part of the peptide into a ring. The ring limits how freely the chain can move, changing the way its receptor-facing amino acids are presented. Researchers use that difference to explore molecular shape and receptor recognition, not simply to compare a seven-amino-acid chain with a longer one.
Which receptors are studied with Melanotan II?
Melanotan II is studied at MC1, MC3, MC4 and MC5 melanocortin receptors. These are separate receptor subtypes, not four names for the same target. Comparing them helps show whether a response is shared across the receptor family or differs by subtype; activity in one receptor assay does not describe every melanocortin-related measurement.
Is Melanotan II a blend of different peptides?
No. Melanotan II is supplied as an individual compound, not a mixture of several melanocortin peptides. Its 10mg strength describes the amount of that molecule. It can be studied at several receptor subtypes because one molecular structure can interact with more than one target, not because the vial contains a separate peptide for each receptor.
What does alpha-MSH analogue mean for Melanotan II?
It means Melanotan II is designed from the melanocortin signalling framework of alpha-MSH, but is not the complete natural hormone. Its shorter, cyclic structure presents a modified set of residues to melanocortin receptors. Researchers compare those designs to understand receptor recognition, rather than assuming that every analogue keeps exactly the parent's activity profile.
Can I buy Melanotan II in the UK for research?
Yes. Lynx supplies 10mg Melanotan II vials for laboratory and in-vitro work in the UK. Live availability is shown on this product page.
How is the Melanotan II batch tested?
UKLY-850 reports 99.759% purity for the 10mg Melanotan II sample, with testing by RP-HPLC + ESI-MS.
