MOLECULAR INFORMATION
Molecular information
- Weight
- 1,024.2 Da
- Length
- 10 amino acids
- Type
- Cyclic heptapeptide · non-selective melanocortin receptor agonist
- Formula
- C₅₀H₆₉N₁₅O₉
Amino acid sequence
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂ Melanotan II is a synthetic non-selective melanocortin receptor agonist originally developed at the University of Arizona as a sunless-tanning agent. Now sold illegally online for cosmetic tanning. Not authorised by any major regulator. Documented harms include rhabdomyolysis, acute kidney injury, malignant melanoma reactivation, and acute psychiatric effects.
Marketed use vs reality
- Cosmetic tanning — heavily marketed; the active mechanism (MC1R agonism) is real but the safety profile is unacceptable for cosmetic use
- Sexual function (erectile effects via MC4R) — marketed; one stopped Phase II trial under the related compound bremelanotide
Why we grade it F
Documented serious adverse events including hospitalisations and one EMA-issued falsified-medicines advisory. ANSM (FR) prohibited it in leave-on cosmetic products under Décret 2026-318. CBG/MEB (NL), BfArM (DE) and MHRA (UK) have issued enforcement actions against online sellers. The harm profile is established; the cosmetic benefit does not justify it.