Melanotan I: Scientific Profile

Publicado el 12 de julio de 2026 · Actualizado el 28 de agosto de 2026

Melanotan I (Afamelanotide, NDP-MSH; CAS 75921-69-6) is a superpotent, proteolysis-resistant synthetic analog of alpha-melanocyte-stimulating hormone (α-MSH). It acts as an agonist of the melanocortin receptors, with predominant affinity for MC1R, stimulating the synthesis of eumelanin. Material intended exclusively for research use.

Melanotan I, known by its international common designation Afamelanotide and by the development code CUV1647, is a synthetic tridecapeptide (13 amino acids) that reproduces and enhances the structure of alpha-melanocyte-stimulating hormone (α-MSH), an endogenous melanocortin peptide derived from the post-translational processing of proopiomelanocortin (POMC). Its molecular formula is C78H111N21O19 and its molecular weight is 1646.85 g/mol (CAS 75921-69-6). In the literature it is also identified by the synonyms [Nle4, D-Phe7]-α-MSH and NDP-MSH, nomenclature that precisely describes the two key modifications introduced to the natural sequence. Melanotan I should not be confused with Melanotan II, a shorter cyclic analog with a distinct pharmacological profile; they are two different compounds.

From a structural standpoint, the native α-MSH sequence is Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. Melanotan I introduces two strategic substitutions: at position 4 the methionine is replaced by norleucine (Nle), a non-proteinogenic amino acid that eliminates the oxidation-susceptible sulfur, and at position 7 the phenylalanine is replaced by its D enantiomer (D-Phe). The peptide retains acetylation at the N-terminus and amidation at the C-terminus. These modifications are responsible for two properties that define the compound: on the one hand, notably greater resistance to enzymatic degradation (proteolysis) compared with natural α-MSH, which has a very short half-life; on the other, a substantial increase in agonist potency, which is why the compound has historically been described as a "superpotent" α-MSH analog. The chirality inversion at position 7 stabilizes the bioactive conformation of the His-Phe-Arg-Trp core, a pharmacophore shared by melanocortin ligands.

The mechanism of action of Melanotan I centers on the family of G-protein-coupled melanocortin receptors (MC1R to MC5R). Its main target, and the best characterized, is the melanocortin 1 receptor (MC1R), prominently expressed in epidermal melanocytes. Activation of MC1R stimulates adenylate cyclase, raises intracellular levels of cyclic AMP (cAMP) and activates the protein kinase A-dependent pathway. This cascade increases the expression of the transcription factor MITF and of key melanogenic enzymes such as tyrosinase, TRP-1 and TRP-2, shifting pigment synthesis toward eumelanin (the brown-black pigment) at the expense of pheomelanin. In research models, this induced melanogenesis has been studied in relation to cutaneous photoprotection, given that eumelanin absorbs and scatters ultraviolet radiation and helps to limit the oxidative damage derived from reactive oxygen species. In addition to MC1R, Melanotan I displays activity on other melanocortin receptor subtypes, which has motivated interest in its potential effects on anti-inflammatory and immunomodulatory pathways explored preclinically.

As for documented research applications, Afamelanotide occupies a particular position within this catalog because, unlike many obscure experimental peptides, it has been the subject of formal pharmaceutical development and of controlled clinical trials. The compound, in its sustained-release subcutaneous implant formulation, has been evaluated and approved by regulatory agencies (the European Medicines Agency and later the U.S. FDA) for the management of erythropoietic protoporphyria (EPP), a rare disease characterized by severe phototoxicity. This clinical context provides a relatively robust body of evidence on the pharmacology, pharmacokinetics, and safety profile of the molecule, which distinguishes it from analogs without clinical development. In the laboratory research field, the compound is used as a reference melanocortin agonist to study MC1R signaling, the regulation of melanogenesis in melanocyte cultures and melanoma cell lines, the mechanisms of pigment-mediated photoprotection, and the oxidative stress response pathways. It has also been explored in preclinical models for its possible anti-inflammatory and tissue-protective effects linked to the melanocortin axis.

The level of evidence for Melanotan I / Afamelanotide is considered clinical with respect to its pharmacological class and its approved application in EPP, with data from human trials and well-characterized pharmacology. Nonetheless, it is important to maintain rigor: much of the use of this material outside the approved regulated context lacks clinical validation, and many of the cosmetic or systemic effects popularly attributed to it do not have the same support. As a melanocortin agonist, it has been described as capable of inducing generalized darkening of the skin, appearance or change of moles and freckles, and transient gastrointestinal or cardiovascular effects in various models and contexts; these observations underscore the need to handle it strictly as a research reagent. Melanotan I is usually supplied as a lyophilized powder that requires reconstitution prior to experimental use.