What is Melanotan 2? Names and origins

Melanotan II and MT2

Melanotan 2, Melanotan II, MT2, MT-2, MT-II and MTII refer to the same synthetic peptide in this file. The broader word melanotan can also be used for Melanotan I, which creates plenty of room for confusion. The historical review of the peptide family describes Melanotan I as linear and Melanotan II as cyclic.

That extra character warrants some fuss because it changes which evidence applies. A result obtained with one member of the family has to travel with its own name.

Arizona’s cyclic peptide

Victor Hruby, Mac Hadley and colleagues at the University of Arizona designed Melanotan II in the late 1980s. It copies part of alpha-MSH, the body’s pigment-stimulating hormone, in a cyclic heptapeptide: seven amino acids held in a constrained structure by an internal lactam bridge. The development account describes the search for potent melanotropic activity and the clinical paths that followed.

The constraint increases resistance to enzymatic breakdown relative to the natural hormone. A small structural constraint with such broad consequences earns my admiration. Its broad receptor activity also means that pigmentation shares the story with appetite, heat production and sexual effects. The mechanism of action starts with those receptors.

Afamelanotide (Melanotan I)

Melanotan I is the linear analogue also called afamelanotide. It has an approved use for erythropoietic protoporphyria, or EPP, a rare inherited condition in which light causes painful skin reactions. Phase 3 trials in people with EPP found longer pain-free sun exposure and fewer phototoxic reactions with afamelanotide. An observational study of 115 patients followed its longer-term use in that condition.

Those are afamelanotide findings in EPP. Melanotan II remains a distinct compound with no approved indication. A family connection cannot transfer an approval or a safety record.

PT-141 and bremelanotide

Bremelanotide, also called PT-141, was developed from the Melanotan II scaffold with an emphasis on sexual-function effects and reduced pigmentation activity. The PT-141 development paper describes that direction. Bremelanotide subsequently became an approved treatment for hypoactive sexual desire disorder in premenopausal women; that approval covers bremelanotide.

The divergences are why I bother with the family tree at all. Combining every successful result under the casual name melanotan erases the useful distinctions.

Hair colour

The small human Melanotan II pigmentation study recorded skin pigmentation, with no controlled hair-colour result reported there. MC1R activity in pigment cells makes the question biologically plausible, but the claims about darker hair circulating among users remain anecdotal accounts. The hair-colour claim remains unsupported by a controlled human outcome.