Melanotan II (CAS 121062-08-6, abbreviation MT-II) is a synthetic cyclic heptapeptide derived from α-MSH (α-Melanocyte Stimulating Hormone, 4-10 amino acid fragment of His-D-Phe-Arg-Trp-Gly-Lys sequence), with Asp-Lys lactam cyclisation conferring superior stability and pan-melanocortin agonism profile. It was developed by the University of Arizona in the 1990s (Dorr 1996) as a theoretical photoprotective agent.
Mechanism of action. MT-II non-selectively activates all four melanocortin receptors: MC1R (melanocytes → melanogenesis, pigmentation), MC3R and MC4R (hypothalamus → satiety, libido, sexual function), MC5R (exocrine glands, skeletal muscle). This pharmacological promiscuity explains its multiple effects profile: tanning (eumelanin), appetite reduction, erection (pro-erectile effect accidentally identified during trials leading to MC4R-selective spin-off PT-141/bremelanotide development).
Pharmacokinetics. MT-II exhibits 1-2 hour plasma half-life after subcutaneous injection, with progressive pigment effect (2-4 weeks to reach plateau). Induced pigmentation is eumelanin (vs phaeomelanin of UV), more protective against UV damage. Frequent adverse effects reported in clandestine use: nausea, hypertension, anorexia, darkening of pre-existing moles (potential interaction with atypical naevi).
Status and research uses. Not approved by FDA, EMA or any regulatory agency for human use. A selective MC1R analogue (afamelanotide, Scenesse®) obtained EMA marketing authorisation (2014) for erythropoietic protoporphyria. MT-II is classified RUO for melanogenesis, appetite regulation and sexual function studies (mouse and rat models). Lab Peptides France markets RUO MT-II in 10mg vials; its certificate of analysis is published on the product page.
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Système mélanocortine, récepteurs MC1R à MC5R, mécanismes pan-agoniste (Melanotan II) et sélectif MC4R (PT-141 bremelanotide, afamelanotide Scenesse), pharmacocinétique, protocoles de reconstitution RUO, stabilité, signaux de sécurité (pigmentation, fonction sexuelle, nausées). Le pilier scientifique de référence.