Melanotan II (MT-2) is a synthetic cyclic peptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH) that activates several melanocortin receptors. It has been studied in research on pigmentation, energy balance and melanocortin signaling in the brain, and its chemistry led directly to the development of bremelanotide. This guide explains what Melanotan II is, what researchers have investigated, and how it is handled in the lab.
What is Melanotan II?
Melanotan II is a seven-residue peptide built around the core sequence that alpha-MSH uses to bind melanocortin receptors. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. Two design choices set it apart from the natural hormone: a lactam bridge between aspartic acid and lysine that locks the peptide into a ring, and a D-phenylalanine in place of the natural L-form. Together these changes make the molecule more resistant to enzymatic breakdown and more potent at melanocortin receptors than native alpha-MSH in experimental systems.
Melanotan II came out of academic research into synthetic melanocortin analogs. A different, linear analog from the same line of work, afamelanotide (sometimes called Melanotan I), later became an approved medicine under the name Scenesse. Melanotan II itself is not an approved medicine in the US or elsewhere, and regulators in several countries have issued public warnings about unlicensed products marketed to consumers. PRIME supplies Melanotan II (MT-2) strictly as a research compound for laboratory use.
How Melanotan II works: mechanism studied in research
The melanocortin system includes five receptors, MC1R through MC5R. Alpha-MSH and related peptides act on these receptors to influence a range of processes. Melanotan II is described in the research literature as a non-selective agonist, meaning it activates several of these receptor subtypes rather than one.
- MC1R: expressed on melanocytes. Activation is linked to production of eumelanin, the darker pigment, which is why MT-2 has been studied in pigmentation research.
- MC3R and MC4R: expressed in the central nervous system and involved in energy balance, food intake and other behaviors in animal studies.
- MC5R: found in peripheral tissues, including exocrine glands; its role is less well characterized.
Because it acts on multiple receptors, Melanotan II produces a broad set of effects in experimental models. That lack of selectivity is a key point in the literature. It is one reason researchers went on to develop more selective melanocortin ligands, and it explains why MT-2 remains useful as a reference tool for probing the melanocortin system as a whole.
Melanotan II is also closely tied to bremelanotide (PT-141). Bremelanotide shares the same cyclic structure but ends in a free carboxylic acid instead of an amide at the C-terminus. It was developed after observations in MT-2 research pointed to central melanocortin effects on sexual function, and it is now FDA-approved as Vyleesi.
Areas of Melanotan II research
Published research on Melanotan II falls into several broad areas:
- Melanogenesis and MC1R signaling in melanocytes
- Pigmentation responses and photobiology in experimental models
- MC4R signaling, food intake and energy balance in rodent models
- Central melanocortin pathways involved in sexual behavior in animal studies
- Structure-activity relationships and receptor selectivity of melanocortin analogs
- Use as a reference agonist in melanocortin receptor pharmacology
Much of this work is preclinical or pharmacological. Melanotan II is not approved to treat any condition, and findings from receptor and animal studies should not be read as evidence of benefit or safety in people.
Melanotan II key facts
| Property | Detail |
|---|---|
| Class | Synthetic cyclic melanocortin peptide (alpha-MSH analog) |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 |
| Other names | MT-2, MT-II, Melanotan 2 |
| Target | Non-selective agonist at melanocortin receptors (MC1R, MC3R, MC4R, MC5R) |
| Form supplied | Lyophilized powder in a sealed vial |
| Research status | Research compound; not an approved medicine |
| Related compounds | Bremelanotide (PT-141), afamelanotide, alpha-MSH |
| Storage | Lyophilized: cold, dry and dark. Reconstituted: refrigerated and protected from light |
Handling and storage of Melanotan II in the lab
Melanotan II is supplied as a lyophilized powder, the most stable form for shipping and storage. Unopened vials are best kept cold and protected from light. Tryptophan-containing peptides such as MT-2 can be sensitive to light and oxidation, so amber storage or a closed box is a sensible habit.
When a solution is needed for an experiment, researchers commonly reconstitute with bacteriostatic water using sterile technique. General practice includes letting the vial reach room temperature, swabbing the stopper, adding diluent slowly down the vial wall, and swirling gently rather than shaking. Reconstituted material is generally stored refrigerated, clearly labeled with the date and concentration, and used within the period set by the lab's own procedures. Repeated freeze-thaw cycles of solutions are best avoided. Our bacteriostatic water guide covers diluent handling in more detail.
Quality and lab results
With a cyclic peptide, confirming that the ring structure and sequence are correct is as important as purity. Every PRIME batch of Melanotan II has a published certificate of analysis, and you can check each batch report on the lab results page. A COA typically confirms identity by mass spectrometry and reports purity by HPLC. Match the lot number on your vial to the report before use and keep it on file with your experiment records.
Related research
Researchers comparing melanocortin compounds will want to read PT-141 vs Melanotan II, which sets out the structural difference and the selectivity question in detail. The PT-141 (bremelanotide) research guide covers the approved derivative on its own, and PRIME also carries PT-141 for melanocortin research.
Melanotan II FAQ
What is the difference between Melanotan I and Melanotan II?
Melanotan I (afamelanotide) is a linear alpha-MSH analog, while Melanotan II is a smaller cyclic peptide. Melanotan II acts more broadly across melanocortin receptors. Afamelanotide is an approved medicine; Melanotan II is a research compound.
Is Melanotan II the same as PT-141?
No, but they are closely related. PT-141 (bremelanotide) has the same cyclic core but a free acid at the C-terminus instead of an amide. PT-141 is FDA-approved as Vyleesi; Melanotan II is not approved.
Which receptors does Melanotan II act on?
Research describes MT-2 as a non-selective agonist at MC1R, MC3R, MC4R and MC5R. Its MC1R activity is linked to pigmentation research, and its MC3R and MC4R activity to studies of energy balance and behavior in animal models.
Is Melanotan II legal or approved?
Melanotan II is not an approved medicine, and regulators in several countries have warned about unlicensed products sold to consumers. PRIME sells it only as a research compound for laboratory use, not for human consumption.
How should Melanotan II be stored?
Keep lyophilized MT-2 cold, dry and away from light. After reconstitution for lab use, store solutions refrigerated, protected from light, and use them within the period defined by your lab's procedures.
For laboratory research use only. Not for human consumption. Not a drug, food or cosmetic.