Melanotan II — Non-Selective Melanocortin Agonist

Background

Melanotan II (MT-II) is a synthetic cyclic analogue of α-melanocyte-stimulating hormone (α-MSH) that binds non-selectively to all five melanocortin receptors (MC1R–MC5R). It was originally synthesised at the University of Arizona in the 1980s as part of a research program into UV-independent skin pigmentation for melanoma prevention.

The original academic program did not progress to approval — a later, more selective compound (afamelanotide / Scenesse®) targeting MC1R alone reached FDA and EMA approval for erythropoietic protoporphyria.

Mechanism

MT-II activates MC1R (melanogenesis in melanocytes), MC3R/MC4R (central appetite suppression and sexual arousal), and MC5R (exocrine gland effects). Its non-selectivity is the source of both its varied effects and its side-effect profile.

What is proven

MC1R-mediated melanogenesis produces measurable skin darkening independent of UV exposure. MC4R-mediated effects on sexual arousal and appetite are also well-characterised pharmacologically.

What is NOT proven (and established risks)

MT-II is not approved for any indication by any major regulator. Its supply through unregulated markets has been linked to multiple documented adverse outcomes including appearance of new naevi (moles), reports of melanoma in users with no other clear risk factor, persistent nausea, hypertension, focal hyperpigmentation, priapism, and rhabdomyolysis. The UK MHRA, Australian TGA, and other national regulators have issued specific public warnings against MT-II use.

Long-term oncological risk in users is not formally quantified by controlled studies but multiple case-series reports raise concern.

Open research questions

Whether selective MC1R agonists (afamelanotide and similar) deliver the desired pigmentation effect without the off-target MC3R/MC4R/MC5R risk; whether reported melanoma cases represent causation or coincidence.

Regulatory status

Not approved by any major regulator. Subject to explicit public-health warnings from the UK MHRA, Australian TGA, the Irish HPRA, and the Norwegian Medicines Agency, among others.

All Proteus® compounds are sold strictly for in-vitro research. Nothing on this page is medical advice, a treatment claim, or a recommendation for human use. Where compounds are licensed medicines in any jurisdiction, that approval applies to the licensed product supplied through a regulated pharmacy — not to research-grade material.