Melanotan-1
[CAS 75921-69-6]

Identification

• Classification: Biochemical >> Peptide
• Name: Melanotan-1
• Synonyms: Melanotropin; 4-Nle-7-phe-alpha-msh; 4-Norleucyl-7-phenylalanine-alpha-msh
• Molecular Formula: C₇₈H₁₁₁N₂₁O₁₉
• Molecular Weight: 1646.85
• Protein Sequence: SYSXEHFRWGKPV
• CAS Registry Number: 75921-69-6
• SMILES: CCCC[C@@H](C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CC1=CN=CN1)C(=O)N[C@H](CC2=CC=CC=C2)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H](CC3=CNC4=CC=CC=C43)C(=O)NCC(=O)N[C@@H](CCCCN)C(=O)N5CCC[C@H]5C(=O)N[C@@H](C(C)C)C(=O)N)NC(=O)[C@H](CO)NC(=O)[C@H](CC6=CC=C(C=C6)O)NC(=O)[C@H](CO)NC(=O)C

Properties

• Density: 1.5±0.1 g/cm³ Calc.^*
• Index of refraction: 1.674 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

chemBlink Chemical Story

Melanotan-1 is an earlier name associated with afamelanotide, a defined analogue of alpha-melanocyte-stimulating hormone. It is not melanotan II, a distinct peptide. Afamelanotide retains a thirteen-residue chain and has two substitutions relative to the natural hormone, including D-phenylalanine in place of the corresponding L residue. Configuration is part of the chemical identity even where the two amino acids have the same elemental composition.

The biological target connects the peptide with pigmentation. Activation of the melanocortin 1 receptor can increase production of eumelanin. That receptor effect motivated research into photoprotection in erythropoietic protoporphyria, a condition in which accumulated protoporphyrin contributes to painful reactions to light. The condition provides the context for the clinical question: whether a defined formulation allows more time in light without pain, not whether a person can achieve a cosmetic tan.

Langendonk and colleagues reported randomized trials examining afamelanotide in that condition. The endpoint gives meaning to the evidence. Time spent in light without pain involves both the biological response and the opportunity to encounter light. It is distinct from a measurement of pigment alone. Clinical results therefore should be read in relation to the enrolled population and the endpoint used, rather than extended to general protection against sun exposure.

The U.S. prescribing information for SCENESSE identifies a regulated implant and an indication involving adults with a history of phototoxic reactions due to erythropoietic protoporphyria. The identity of its active substance does not authenticate other materials marketed under the historical name. A matching name cannot establish preparation quality, delivery characteristics, or safety. This is why both the chemical name and the clinical context belong in the account: a synthetic peptide helped test a specific response to a serious photosensitivity disorder, without establishing cosmetic or general preventive use.

References:
1. FDA GSRS. Afamelanotide, CAS 75921-69-6. https://precision.fda.gov/uniisearch/srs/unii/qw68w3j66u
2. Langendonk JG et al. Afamelanotide for erythropoietic protoporphyria. NEJM (2015). https://doi.org/10.1056/NEJMoa1411481
3. DailyMed. SCENESSE prescribing information. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=94f53286-11dd-7fbb-e053-2a95a90a7c48

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