Of the melanocortin analogues studied in the literature, MT-1 is the one with the clearest receptor story. Where related compounds hit several melanocortin receptors at once, MT-1 is comparatively selective, and that selectivity is the reason it has the research record it does.
If you are weighing MT-1 against MT-2, our Melanotan 1 vs Melanotan 2 comparison covers the differences side by side.
What MT-1 is
MT-1, also known as afamelanotide, is a synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH). The native hormone is a thirteen-residue peptide; the analogue carries substitutions that increase both its stability and its potency relative to the natural sequence.
It is worth being precise about naming, because the literature is inconsistent. Afamelanotide, melanotan I and MT-1 all refer to the same compound. MT-2 is a structurally distinct peptide with a different receptor profile and should not be treated as a variant of the same molecule.
The melanocortin receptor family
There are five melanocortin receptors, MC1R through MC5R, all G protein-coupled. They are distributed across very different tissues and mediate quite different processes. MC1R is associated principally with pigmentation; MC4R with energy balance and feeding behaviour.
Receptor selectivity is therefore the single most important property distinguishing one melanocortin analogue from another. A compound that activates MC1R alone will behave very differently in an experimental system from one that activates MC1R and MC4R together.
Structural basis
A 2021 paper in Cell Research resolved the structural mechanism of hormone recognition at the human MC1R, including the role of calcium in ligand binding.[3] Structural work of this kind is what allows selectivity to be understood in molecular terms rather than inferred from functional assays alone.
What the published research examines
MT-1 has an unusually substantial clinical literature for a compound in this class, because it progressed through formal development for erythropoietic protoporphyria, a rare photosensitivity disorder. Kim and Deeks reviewed that evidence in the American Journal of Clinical Dermatology.[1]
Minder and colleagues published a detailed pharmacokinetic and pharmacodynamic analysis in Clinical Pharmacokinetics, which remains the most complete account of how the compound behaves over time.[2] A 2024 review in Postepy Dermatologii i Alergologii extended the survey across protoporphyria and other dermatological contexts.[4]
For laboratory work this body of literature is useful mainly because it provides well-characterised reference data on a melanocortin agonist, which is comparatively rare in this compound class.
Handling and stability
MT-1 is supplied as a lyophilised solid, stored at −20°C and protected from light and moisture. Reconstitution follows the standard approach for peptides of this length: sterile solvent added slowly down the vial wall, gentle swirling, no vortexing or vigorous shaking.
Melanocortin analogues are sensitive to repeated freeze-thaw cycling. Where a reconstituted stock will be used across multiple experiments, aliquoting into single-use volumes at the point of reconstitution avoids degrading the whole stock through repeated cycles.
What the literature does not establish
Selectivity is relative, not absolute. MT-1 is more MC1R-selective than related analogues, but selectivity varies with concentration, and at sufficiently high concentrations most receptor-selective ligands lose that selectivity. Experimental designs that assume clean single-receptor activation without verifying concentration ranges are making an assumption the pharmacology does not support.
References
- Kim ES. Afamelanotide: A Review in Erythropoietic Protoporphyria. American Journal of Clinical Dermatology. 2016. PMID 26979527
- Minder EI. Pharmacokinetics and Pharmacodynamics of Afamelanotide and its Clinical Use in Treating Dermatologic Disorders. Clinical Pharmacokinetics. 2017. PMID 28063031
- Ma S. Structural mechanism of calcium-mediated hormone recognition and Gβ interaction by the human melanocortin-1 receptor. Cell Research. 2021. PMID 34453129
- Polańska A. Afamelanotide in protoporphyria and other skin diseases: a review. Postepy Dermatologii i Alergologii. 2024. PMID 38784937
Research use only
MT-1 is supplied by MMpeptides strictly for laboratory and in vitro research. It is not approved for human or veterinary use, is not a cosmetic or medicinal product, and nothing in this article should be read as describing use in people. Third-party studies are cited for scientific context only. Researchers are responsible for observing all applicable regulations in their jurisdiction.