Melanotan I (Afamelanotide)

Melanotan I is a synthetic analog of alpha-melanocyte-stimulating hormone (alpha-MSH). Its structure, [Nle4, D-Phe7]-alpha-MSH, keeps the 13-residue length of alpha-MSH with two substitutions that make it more stable and more potent at melanocortin receptors. It carries CAS number 75921-69-6 and the molecular formula C78H111N21O19, with a molecular weight of 1646.8 g/mol.

Under the name afamelanotide, this molecule reached approval for a specific medical use. It is supplied here as a research compound in lyophilized powder form for laboratory reconstitution.

Melanotan I came out of melanocortin research at the University of Arizona in the 1980s. A 2021 review by Wu and Cotliar in the Journal of Drugs in Dermatology described afamelanotide as an orphan drug with broad dermatologic research interest (PubMed 33683075).

A 2021 review by Searle and colleagues in Clinical and Experimental Dermatology placed it within systemic photoprotection research (PubMed 33872410), and a 2025 cohort study by Homey and colleagues in Photodermatology, Photoimmunology and Photomedicine reported longer-term observational data (PubMed 40082741).

Melanotan I acts as an agonist at melanocortin receptors, with activity at MC1R that is studied in connection with melanin production in skin models. The substitutions in its sequence slow its breakdown and increase receptor binding compared with natural alpha-MSH.

It is more receptor-broad than the cleaner melanocortin agonists and differs from PT-141, which is studied mainly for central MC4R signaling. For current findings, search PubMed directly.

Lyophilized Melanotan I is generally stored at -20°C for long-term holding, with stability reported around 24 months. Refrigeration at 2°C to 8°C suits shorter windows, away from light and moisture.

The lot-specific Certificate of Analysis is the authoritative reference for a given batch.

Reconstitution means returning a lyophilized compound to solution. This page gives no preparation procedure: solvent, concentration and handling steps belong to the methodology of the study being reproduced, not to a compound reference. Melanotan I is handled as aqueous-soluble material.

Lyophilized material is hygroscopic, so a sealed container is allowed to reach ambient temperature before it is opened. Solubility and water-content figures for a given lot appear on its Certificate of Analysis.

Identity and purity of research-grade Melanotan I are established analytically, by HPLC with mass spectrometric confirmation of the expected mass. Verified purity is documented per lot on the Certificate of Analysis.

Check HPLC purity, mass-spec identity, and net peptide content on the Certificate of Analysis. peptides.com publishes lot-specific lab reports for verification.

Melanotan I is grouped with the melanocortin receptor agonists:

• Melanotan II.
  A cyclic melanocortin agonist with broader receptor activity. 
• PT-141.
  A melanocortin agonist studied for central signaling. 
• GHK-Cu.
  A separate skin-context research peptide. 

Wu J, Cotliar R, et al. (2021). Afamelanotide: An Orphan Drug with Potential for Broad Dermatologic Applications. Journal of Drugs in Dermatology.
PubMed 33683075

Searle T, Ali FR, et al. (2021). Systemic photoprotection in 2021. Clinical and Experimental Dermatology.
PubMed 33872410

Homey B, Schelonke K, et al. (2025). German Cohort Observational Study of afamelanotide. Photodermatology, Photoimmunology and Photomedicine.
PubMed 40082741

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• Documentation: COA and Lab Testing.

These products are sold for Research Use Only and are not intended for human consumption.