Melanotan I (MT-1)

Melanotan I (MT-1), also known by the non-proprietary name afamelanotide in its approved form, is a synthetic peptide analogue of the endogenous hormone α-Melanocyte-Stimulating Hormone (α-MSH). It is a linear peptide composed of 13 amino acids.

The primary mechanism of action for Melanotan I is to function as an agonist for the melanocortin receptors, with a high affinity for the Melanocortin 1 Receptor (MC1R). The activation of the MC1R in melanocytes (skin pigment cells) stimulates the process of melanogenesis, which is the production of melanin, particularly the darker, more photoprotective eumelanin. This action results in increased skin pigmentation, or tanning, independent of significant UV radiation exposure.

Compared to its more well-known counterpart, Melanotan II (MT-2), Melanotan I is more selective for the MC1R and has a less pronounced effect on other melanocortin receptors that influence functions like libido and appetite. It was initially developed as a potential photoprotective agent, a concept that led to the development of the approved drug afamelanotide, which is used to treat erythropoietic protoporphyria, a rare photosensitivity disorder.