Melanotan II

Melanotan II is a synthetic cyclic analogue of alpha-melanocyte-stimulating hormone (alpha-MSH) with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. Its cyclic structure gives it higher metabolic stability and broader melanocortin receptor affinity (MC1R, MC3R, MC4R, MC5R) compared to the linear Melanotan I. In preclinical research, Melanotan II has been studied for melanogenesis and skin pigmentation pathways, MC4R-mediated energy homeostasis, MC3R/MC5R receptor pharmacology, and sexual function and arousal research models. CAS: 121062-08-6; MW: 1024.18 Da. Supplied at 99.1% HPLC purity.

Legal status: Melanotan II is legal to purchase in Australia for legitimate laboratory research purposes. It is not listed as a scheduled substance under the Poisons Standard when sold for research use only. Purchasers must be 18+. Not for human consumption, therapeutic, cosmetic, or veterinary use — important note: Melanotan II is not approved for any therapeutic use in Australia and must not be represented as such. Quality: Batch PW-260309, independently verified at 99.1% HPLC purity. COA includes: HPLC purity %, mass spectrometry identity confirmation, and sterility screening. Full COA in our COA Library.

Reconstitution: Using a 31G syringe, draw 1–2mL of bacteriostatic water. Inject slowly down the inside glass wall of the vial — never directly onto the lyophilised cake. Gently swirl until fully dissolved. Solution should be clear and colourless. Common concentration: 1mL BAC water per 10mg = 10mg/mL. Storage: Lyophilised — store at −20°C, protected from light and moisture, for 12–24 months. Reconstituted — refrigerate at 2–8°C and use within 4 weeks. Melanotan II is light-sensitive in solution — wrap vial in foil or keep in a dark container after reconstitution.

While both are alpha-MSH analogues, they have important structural and pharmacological differences. Melanotan I is a linear peptide (MW 1646.87 Da) with selective MC1R affinity — making it a more targeted tool for pigmentation and photoprotection research. Melanotan II is a cyclic peptide (MW 1024.18 Da) with broader melanocortin receptor affinity (MC1R, MC3R, MC4R, MC5R), which means it engages a wider range of physiological pathways. For research specifically targeting pigmentation: Melanotan I is more selective. For broader melanocortin receptor pharmacology research: Melanotan II offers more receptor coverage. They are not interchangeable research tools.

Melanotan II is a non-selective melanocortin receptor agonist that binds to MC1R, MC3R, MC4R, and MC5R with nanomolar affinity. Reported Ki values: MC1R ~0.21 nM; MC3R ~0.66 nM; MC4R ~0.53 nM; MC5R ~1.7 nM. This broad receptor profile is in contrast to Melanotan I (afamelanotide), which has much greater selectivity for MC1R. The MC4R binding of Melanotan II is the basis for its research in energy homeostasis and MC4R pharmacology. MC5R binding is associated with exocrine gland function research models. Not for human consumption — for research use only.

MC4R (melanocortin-4 receptor) is expressed in the hypothalamus and other CNS regions and is one of the most studied GPCRs in metabolic and neuroscience research. Key research applications involving MC4R agonism (via Melanotan II or selective MC4R agonists) include: energy homeostasis research — MC4R is a central regulator studied in metabolic research models; sexual function and erectile function research in rodent models; gut motility and gastric emptying research; and autonomic nervous system regulation. MC4R is a major target in metabolic-pathway research. Not for human consumption — for research use only.

Melanotan II is a non-selective melanocortin agonist studied across several receptors, including MC1R (linked to pigmentation pathways) and MC4R (linked to central nervous-system pathways). This broad receptor activity distinguishes it from the more MC1R-selective Melanotan I in research models. Not for human consumption — for research use only.

Melanotan II is non-selective and shorter (a cyclic heptapeptide), engaging multiple melanocortin receptors, whereas Melanotan I is a linear, more MC1R-selective analogue. Researchers choose between them based on the receptor selectivity their protocol requires; they are distinct and non-interchangeable research tools. Not for human consumption — for research use only.

Store the lyophilised vial at −20°C for up to 24 months. After reconstitution in bacteriostatic water, refrigerate at 2–8°C, protect from light, and use within about 4 weeks, avoiding repeated freeze-thaw cycles. Confirm the solution is clear before use. Not for human consumption — for research use only.

Melanotan II is commonly written Melanotan 2, MT-2, MT-II or simply MT2. All of these refer to the same melanocortin (MC1R and MC4R) research peptide. For in-vitro research use only.