Melanotan I

What it is

Melanotan I is built to act mainly on the MC1 receptor, the cell signal that tells skin cells called melanocytes to produce melanin. This selectivity for one receptor type is a feature researchers highlight when comparing it with other melanocortin peptides that act more broadly across several receptor types.

Doctors turn to an implant form of this molecule, marketed under the approved name SCENESSE, when treating a rare condition called erythropoietic protoporphyria, in which sunlight exposure causes severe pain. That approved use is distinct from the separate research question of whether an injectable, non-implant form of the same molecule can be used to study tanning and protection from ultraviolet light.

How it is studied

Human studies, mostly from one research group at the University of Arizona and a separate Australian group, have given repeated injections under the skin over one to three ten day courses, sometimes paired with a small, controlled amount of ultraviolet light, while tracking skin pigment changes, sunburn cell counts, and general tolerability. One early trial paired the peptide with sunscreen rather than intentional ultraviolet exposure, to see whether skin would darken without any light trigger at all.

What studies report

• Three small phase 1 trials, together covering 24 subjects, reported that melanotan I combined with UV-B light or sunlight was tolerated with only minor side effects, mainly nausea and temporary facial flushing, and no visible tissue damage at any treated site. [1]
• Those same trials reported that treated subjects tanned more than sunlight alone produced, needed roughly half as much sun exposure time for the same amount of tanning, and kept a darker tan for at least three weeks longer than untreated subjects. [1]
• A separate placebo-controlled trial in 65 fair skinned volunteers reported that melanin density in the skin rose significantly after treatment, and that a standard amount of UV light produced more than 50 percent fewer sunburned skin cells and 59 percent less UV-related DNA damage in treated skin. [2]
• An earlier randomized, placebo-controlled trial in 28 healthy men, conducted with subjects wearing high-potency sunscreen throughout, reported that the treated group's skin darkened measurably over several weeks while the placebo group's skin did not darken at all. [3]

What is not known

All of the human evidence located for this entry comes from small phase 1 style trials, run mostly by the same University of Arizona research group that first developed the peptide, so it is not known how well these findings would replicate in an independent, larger trial. How injectable, non-implant use compares with the approved implant's safety record over months or years is not addressed in these studies. Effects on existing moles or skin lesions over long term repeated use are not covered by the short studies cited, and whether tanning achieved this way changes long term skin cancer risk has not been studied in the material reviewed here.

Reported adverse findings

• Across the three phase 1 trials, the main side effects reported were mild nausea and transient facial flushing, with no pathological skin findings at any UV-exposed or sun-exposed site. [1]

Regulatory status

An implant form of this molecule, afamelanotide, marketed under the approved name SCENESSE, is approved by the United States Food and Drug Administration for a specific rare condition, erythropoietic protoporphyria. No regulator has cleared injectable, non-implant forms studied for tanning or photoprotection for ordinary human use.