Melanotan 2 20 mg PEN

MELANOTAN 2 20 mg PEN — α-MSH analogue in a pre-dissolved pen for laboratory research

MELANOTAN 2 20 mg PEN is a research reagent (Research Use Only) in a pre-dissolved pen format. Melanotan 2 (MT-2) is not authorised as a medicine in any major jurisdiction (EMA, FDA). It is a synthetic α-MSH analogue intended solely for laboratory research into the pharmacology of melanocortin receptors. It is not a cosmetic product, a tanning agent, a supplement or a product for use in humans. Related, authorised melanocortin analogues (afamelanotide, bremelanotide) are distinct molecules with their own narrow medical indications — they are not identical to MT-2.

Melanotan 2 is one of the most extensively described synthetic analogues of the melanotropic hormone α-MSH (alpha-melanocyte-stimulating hormone) in the literature. The molecule was developed at the University of Arizona during the 1980s and 1990s as part of the work carried out by the teams of Victor Hruby and Mac Hadley on the pharmacology of pigmentation. MT-2 is a non-selective melanocortin receptor agonist — it binds and activates the MC1R, MC3R, MC4R and MC5R receptors, which makes it a valuable tool for studying the entire family of these receptors.

In the One Peptides catalogue, Melanotan 2 functions as an RUO chemical reagent in a pre-dissolved pen format. This format simplifies laboratory work: it does not require reconstitution of a lyophilisate and allows precise withdrawal of the peptide under controlled conditions. It is a technical solution for researchers working with the melanocortin system in in vitro and in vivo models — not a form for administration to humans.

What Melanotan 2 is — sequence and class

Melanotan 2 is a cyclic α-MSH analogue — a synthetic peptide designed as a more stable and more potent counterpart of the natural melanotropic hormone. Natural α-MSH has a very short serum half-life (minutes); cyclisation and amino-acid substitutions in MT-2 extend its stability and increase its affinity for melanocortin receptors.

Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂ — a cyclic heptapeptide core with a D-phenylalanine residue and a lactam bridge stabilising the conformation. These modifications account for its resistance to enzymatic degradation and its high receptor activity towards α-MSH.

Chemical characterisation

Mechanism of action in research

Melanotan 2 activates the family of melanocortin receptors — G protein-coupled receptors whose stimulation increases the intracellular concentration of cAMP. The individual subtypes are responsible for the various physiological effects studied in the literature.

MC1R — melanogenesis. The MC1R receptor on the surface of melanocytes regulates eumelanin synthesis. Activation of MC1R triggers the cAMP → MITF → tyrosinase pathway, leading to the production of dark pigment. In cellular and animal models, MT-2 stimulates melanogenesis more strongly than native α-MSH — this is the basis for using MT-2 as a tool for studying pigmentation.

MC4R — central signalling. The MC4R receptor in the central nervous system is involved in the regulation of appetite, energy expenditure and pathways related to sexual function. It was on the basis of selective MC4R stimulation that a separate, authorised molecule was developed — bremelanotide. In research, MT-2 serves as a reference agonist for this receptor.

MC3R and MC5R. MC3R takes part in the regulation of energy homeostasis and in inflammatory processes; MC5R is associated with the function of exocrine glands. The non-selectivity of MT-2 means that it stimulates all four subtypes — an advantage in studies of the entire receptor family, and a limitation where selectivity for a single subtype is required.

The reference data on MT-2 derive mainly from cellular models (melanocyte cell lines), animal models of pigmentation and early pharmacological studies of the melanocortin system.

Melanotan 2 (RUO) vs authorised melanocortin analogues

Conceptual confusion has built up around MT-2, because molecules authorised as medicines also derive from melanocortin chemistry. These are, however, distinct substances with a distinct status.

Melanotan 2 is none of the authorised melanocortin medicines. Afamelanotide and bremelanotide are different molecules, with a different selectivity profile, authorised for narrow, specific indications under medical supervision. As an RUO reagent, MT-2 does not have the status of a medicinal product and is not intended for any use in humans.

Applications in scientific research

As an RUO reagent, Melanotan 2 finds use in several directions.

Pharmacology of melanocortin receptors. Analyses of receptor activity across the four MCR subtypes, EC50 measurements in cell cultures with cAMP reporters, agonist profiling and comparisons with selective ligands. The non-selectivity of MT-2 makes it a useful reference agonist for the entire family.

Melanogenesis studies. Cellular melanocyte models and melanoma cell lines (B16) for studying the tyrosinase/MITF pathway, the regulation of eumelanin synthesis and the pigmentation response to MC1R agonists.

Models of central energy regulation. Studies of the role of MC4R and MC3R in energy homeostasis, appetite and energy expenditure — MT-2 as a tool for stimulating melanocortin pathways in animal models.

Comparative analyses of melanocortin ligands. Comparisons with selective agonists (for example MC4R-selective compounds) and antagonists in work on structure–activity relationships (SAR) within the melanocortin system.

One Peptides quality specification

Each Melanotan 2 pen undergoes a five-stage analytical control process.

• HPLC ≥98% — the area of the main peak is ≥98% of the total peak area (liquid chromatography with UV detection).
• MS confirmation — confirmation of peptide identity by molecular mass (~1024 Da).
• COA per batch — a public certificate of analysis for each batch (theoretical/measured mass, HPLC profile, synthesis date, batch number).
• Cold chain 2–8°C — a monitored cold chain from synthesis to delivery.
• Batch traceability — the batch number in three places: pen label, invoice and COA.

Working with the pre-dissolved pen in a laboratory protocol

The following guide describes the technical handling of the pen in the context of a laboratory research reagent. It does not constitute instructions for administration to humans or animals — a pen traded as RUO is not a pharmaceutical dosage form.

Pen contents. The Melanotan 2 PEN contains 20 mg of pre-dissolved MT-2 in solution (the volume configuration may vary depending on the batch — see the COA for details).

Working with the pen. The solution is withdrawn using a laboratory syringe or a dosing applicator with microlitre precision. The solution should be clear — cloudiness, sediment or a change in colour are a signal that the batch is not suitable for further work.

Working solutions. For in vitro receptor assays, the picomolar to nanomolar scale is used as standard. Working solutions are prepared by serial dilutions in PBS at pH 7.4 or in buffers compatible with the specific experimental system.

Stability. Unopened pen: typically up to 24 months at 2–8°C, protected from light (see the COA for details). After first opening: typically up to 28 days at 2–8°C. Freeze–thaw cycles should be avoided. MT-2 is light-sensitive — the solution is stored in a vial protected from UV exposure.

The peptide calculator makes it easier to convert the starting concentration from the pen to the desired working concentration when planning serial dilutions.

Safety and limitations in the light of research

Melanotan 2 is a pharmacologically active substance with a broad, non-selective profile of action on melanocortin receptors. The literature and reports document a number of effects relevant to risk awareness when working with the reagent:

• Darkening of naevi and freckles. Stimulation of MC1R intensifies melanogenesis not only in the skin generally, but also in existing pigmented naevi — enlargement and darkening of pigmented lesions has been documented. This warrants legitimate oncological vigilance: case reports of melanoma and dysplastic lesions have appeared in the literature in the context of MT-2 use in humans. The causal relationship has not been established, but the signal calls for caution.
• Nausea and facial flushing — frequently reported effects of melanocortin activation, particularly on first exposure.
• Spontaneous erections — a consequence of MC4R stimulation; this is the same mechanism on which the selective medicine bremelanotide was based.
• Reduced appetite — a result of central action on MC4R/MC3R.
• No authorisation and no long-term data. MT-2 has not undergone full regulatory studies — its long-term safety profile in humans remains undetermined.

This information is scientific and cautionary in character and concerns risk awareness, not instructions for use. Working with MT-2 in a research setting requires the standard precautions for biologically active peptides.

Frequently asked questions

How does Melanotan 2 differ from melanocortin medicines (Scenesse, Vyleesi)?
They are distinct molecules. Melanotan 2 is a non-selective agonist of all four melanocortin receptors and has the status of an RUO reagent. Afamelanotide (Scenesse) acts predominantly on MC1R and is authorised for erythropoietic protoporphyria; bremelanotide (Vyleesi) acts predominantly on MC4R and is authorised for HSDD. MT-2 is not identical to any of them and does not have medicine status.

Is Melanotan 2 a tanning agent?
No. It is a chemical reagent for laboratory research into the pharmacology of melanocortin receptors and melanogenesis. It is not a cosmetic product or a tanning agent and is not intended for use in humans.

Why is MT-2 called non-selective?
Because it activates all four subtypes of the melanocortin receptors (MC1R, MC3R, MC4R, MC5R), unlike ligands designed to stimulate a single subtype. Non-selectivity is an advantage in studies of the entire receptor family, and a limitation where selectivity is required.

What is the molecular formula and mass of Melanotan 2?
The molecular formula is C₅₀H₆₉N₁₅O₉, with a molecular mass of approximately 1024.2 Da. The molecule is a cyclic α-MSH analogue with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂. The identity of each batch is confirmed by mass spectrometry.

How long does the pen retain activity after first opening?
Typically up to 28 days at 2–8°C from the first withdrawal. Detailed stability data are in the batch COA. MT-2 is light-sensitive — the solution should be protected from UV exposure. Freeze–thaw cycles should be avoided.

Is Melanotan 2 on the WADA list?
Melanotan 2 does not appear as a separate entry on the current WADA prohibited list. Its status may change — verification of current guidance rests with the researcher.

Bibliography

1. Hadley ME, Hruby VJ et al. Discovery and development of novel melanogenic drugs — Melanotan-I and -II
2. Dorr RT et al. (1996). Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study
3. Wessells H et al. (2000). Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction
4. King SH et al. (2007). Melanocortin receptors, melanotropic peptides and penile erection

Research Use Only chemical reagent. Melanotan 2 20 mg PEN in the One Peptides catalogue is not a medicinal product, a cosmetic, a dietary supplement or a foodstuff. It is not intended for administration to humans or animals outside a controlled experimental setting, nor for any application in tanning, skin pigmentation or the modulation of sexual function in humans. Melanotan 2 holds no EMA or FDA authorisation as a medicine. The authorised melanocortin analogues (afamelanotide, bremelanotide) are distinct molecules with a distinct status. The information in this description is educational and scientific in character and refers to results reported in the literature — it does not constitute medical or cosmetic advice or instructions for administration.