MT-1 vs MT-2: Why They're Different

Melanotan 1 and Melanotan 2 are often discussed together, but they are quite different molecules.

MT-1 (afamelanotide) is a linear 13-amino-acid α-MSH analog, selective for the MC1R receptor, and its biological activity is essentially melanin production. It is the FDA-approved form (for EPP).

MT-2 is a cyclic 7-amino-acid analog that is far less selective — it hits multiple melanocortin receptors (MC1R, MC3R, MC4R, MC5R), which is why it produces not just tanning but also significant aphrodisiac effects and appetite suppression, and a much rougher side-effect profile (nausea, mole darkening, priapism risk).

The selectivity difference is the whole story: MT-1 is a targeted photoprotection drug; MT-2 is a broad melanocortin agonist with a wide and unpredictable effect profile. The thread below unpacks the receptor pharmacology and why members treat the two peptides very differently.