Melanotan II 10mg (MT-II)

Melanotan II (MT-2) is a synthetic analogue of the alpha-melanocyte-stimulating hormone (α-MSH), initially developed in the 1980s at the University of Arizona. This peptide was designed to mimic the effects of α-MSH, primarily focusing on inducing skin pigmentation without the need for UV exposure. MT-2 has since been the subject of extensive research due to its ability to bind to melanocortin receptors, particularly MC-1R and MC-4R, which are involved in a variety of physiological processes.

Research has demonstrated that Melanotan II can influence several biological functions beyond skin pigmentation. These include modulation of sexual arousal, appetite suppression, and potential anti-diabetic effects. The peptide exerts its effects by interacting with melanocortin receptors, which are part of the G protein-coupled receptor family, playing crucial roles in energy homeostasis, sexual function, and pigmentation.

Melanotan II is a cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone. Two structural changes define it. The sequence is cyclised through a lactam bridge between an aspartate and a lysine side chain, which locks the His-Phe-Arg-Trp pharmacophore into the conformation that melanocortin receptors recognise, and the phenylalanine is the D-isomer, which resists proteolysis. Together these give far greater potency and duration than the native hormone, which is degraded within minutes.

The pharmacologically important property, and the source of its effect profile, is that it is non-selective. Melanotan II is an agonist at melanocortin receptors broadly rather than at one subtype. MC1R mediates pigmentation, MC3R and MC4R are central receptors involved in energy balance and sexual function, and MC5R has exocrine roles. A non-selective agonist engages several of these at once, which is why its reported effects span pigmentation, sexual arousal, appetite suppression and nausea in the same molecule.

That lack of selectivity is the reason the compound was not developed further while a selective derivative was. Bremelanotide, the metabolite in which the C-terminal amide is replaced by a free acid, retains melanocortin activity with a different profile and was developed for sexual dysfunction. Afamelanotide, a linear MC1R-preferring analogue, was developed for a photoprotection indication. Melanotan II sits between them and is selective for nothing.

Melanotan II primarily exerts its effects through binding to melanocortin receptors, namely MC-1R and MC-4R. MC-1R is predominantly expressed in melanocytes, where it plays a significant role in skin pigmentation by increasing melanin production. A study by Wakamatsu et al. (2006) demonstrated that MT-2 effectively stimulates melanogenesis, which can lead to enhanced skin tanning without UV exposure.

MC-4R, on the other hand, is involved in regulating energy homeostasis and sexual behavior. Research by Van der Ploeg et al. (2002) showed that activation of MC-4R by MT-2 can lead to increased sexual arousal and reduced food intake. These findings suggest a potential application of MT-2 in studying the regulation of appetite and sexual function through the melanocortin pathway.

Studies have shown that Melanotan II can influence appetite and energy regulation. In rodent models, MT-2 administration resulted in a decrease in food intake and a shift in dietary preferences away from high-fat foods. This effect is thought to be mediated through the activation of MC-4R, which plays a role in the leptin-independent satiety pathway (Fan et al., 1997).

The implications of these findings are significant for research into obesity and metabolic disorders. By modulating the melanocortin pathway, MT-2 provides a valuable tool for investigating the mechanisms underlying appetite control and energy expenditure.

Research indicates that Melanotan II may have anti-diabetic properties. A study by Cettour-Rose et al. (2005) found that MT-2 administration in animal models led to improved glucose tolerance and insulin sensitivity. These effects are believed to be mediated through melanocortin receptor pathways, which influence glucose metabolism and energy homeostasis.

These findings suggest that MT-2 could be a valuable research tool for exploring new therapeutic strategies for diabetes management, particularly in understanding how melanocortin receptors can be targeted to regulate glucose levels.

In addition to its metabolic effects, Melanotan II has been studied for its potential impact on behavior and neurological functions. Research by Modica et al. (2010) demonstrated that MT-2 could reverse autistic-like behaviors in mouse models by increasing oxytocin receptor expression in the brain. This highlights the peptide's potential in studying neurodevelopmental disorders.

Furthermore, MT-2 has shown promise in reducing compulsive and addictive behaviors. A study by Ploj et al. (2002) found that MT-2, in combination with naltrexone, significantly reduced binge-like ethanol intake in animal models. These findings underscore the peptide's potential utility in addiction research.

There are five melanocortin receptor subtypes with substantially different roles. MC1R on melanocytes controls pigmentation. MC2R is the adrenocorticotropic hormone receptor. MC3R and MC4R are central receptors involved in energy balance, and MC4R in particular in sexual function. MC5R has exocrine roles.

Melanotan II activates melanocortin receptors broadly rather than selectively. That single fact explains its entire effect profile: pigmentation from MC1R, sexual arousal and appetite suppression from central receptors, nausea and flushing from the same central engagement. These are not separable side effects of a pigmentary agent; they are parallel consequences of one non-selective agonist.

This is intrinsic to the molecule and not a matter of dose. A dose low enough to avoid central effects would also be too low for the pigmentary effect, because the same molecule reaches both receptor populations.

Melanotan II, bremelanotide and afamelanotide are related and are often conflated, including on product listings. They are different molecules with different regulatory histories.

Bremelanotide is the free-acid metabolite of melanotan II, differing at the C-terminus where the amide is replaced by a carboxylic acid. It was developed specifically for sexual dysfunction and reached approval in that indication. Afamelanotide is a linear alpha-MSH analogue with MC1R preference, developed and approved for photoprotection in erythropoietic protoporphyria.

Melanotan II itself was not developed to approval in any indication. Reading approval of a related compound as evidence for this one is an error the naming actively encourages, and the C-terminal difference between melanotan II and bremelanotide is a single functional group that changes the molecule's identity and its regulatory status entirely.

For most compounds in this catalogue the published safety record is thin because there has been little human exposure. Melanotan II is different: it has had substantial unsupervised human use, and a case-report literature has accumulated as a result, including reports of renal infarction and of changes in melanocytic naevi.

Case reports establish that something can happen, not how often it does. They cannot give incidence, and they are subject to reporting bias in both directions. They are nonetheless the only human safety information available for this compound, because no controlled programme generated any.

It has no marketing authorisation in any jurisdiction and has been the subject of regulatory warnings in several countries. Material supplied for research is for in-vitro laboratory use only and is not a medicine.

The lactam bridge makes this a cyclic peptide, and cyclisation is part of the identity rather than a refinement. A linear species of the same composition has the same amino acid content but differs in mass by the water lost on cyclisation, and it will not have the constrained conformation the receptors recognise.

The tryptophan residue is oxidation-prone and light-sensitive, which makes storage in the dark more than a formality for this sequence. The C-terminal amide is also specified; the free acid is bremelanotide, a different compound, so a mass reported one dalton higher is not an impurity but a different molecule.