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Terminus Peptides
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  • 55 compound profiles, every source cited
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Research profile · Peptide

Melanotan II

Also known as MT-II

Early human — evidence level 3 of 4: Early human evidenceExperimental — UK regulatory status: Experimental — not authorised for human use in the UK

Overview

A non-selective melanocortin receptor agonist. The MHRA has repeatedly acted to remove products containing it from the UK market.

Category
Peptide
Highest evidence level identified
Early human evidence
Last scientifically reviewed
20 August 2026
Last regulatory review
20 August 2026

Mechanism under investigation

Melanotan II is a synthetic cyclic analogue of alpha-melanocyte-stimulating hormone acting as a non-selective agonist across melanocortin receptors. Activation of the MC1 receptor is the proposed basis for increased melanogenesis and skin darkening, while activity at the MC3 and MC4 receptors is the proposed basis for the effects on sexual arousal and appetite reported in early human work. Because it is non-selective its effects are diffuse, and the relative contribution of each receptor to any given effect in humans is not well characterised.

Research areas

  • Melanocortin signalling
  • Pigmentation research

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

Melanocortin receptor binding and melanogenesis assays support broad, non-selective agonism.

Animal evidence

Studies in living non-human animals.

Pigmentation, erectile and appetite-suppressant effects have been demonstrated across species, and this work drove wider interest in the melanocortin system.

Human observational evidence

Studies observing people without assigning an intervention.

No cohort or surveillance studies exist. What exists instead is an accumulating case-report literature on harms — a weaker form of evidence, though notably consistent in direction.

Clinical-trial evidence

Studies assigning an intervention to human participants.

Limited and historical. The principal example is a double-blind placebo-controlled crossover study in ten men with psychogenic erectile dysfunction, published in 1998, in which clinically apparent erections developed in eight of ten. Transient nausea, stretching, yawning and decreased appetite were reported more often than on placebo. No trial has ever been conducted for cosmetic tanning, which is the use the compound is actually sold for.

Study limitations

  • The only controlled human trial had ten participants, was conducted for erectile dysfunction, and dates from 1998. It says nothing about the cosmetic use for which the compound is sold.
  • There is no controlled safety data at all for repeated or long-term use, which is precisely the pattern of real-world use.
  • The harms literature is composed of individual case reports. These establish plausible association but cannot establish incidence or causation.
  • Products are unregulated and their actual content is unverified. A forensic analysis of a seized vial labelled as this compound determined its purity at 30 per cent.

UK regulatory context

Experimental — not authorised for human use in the UK

A compound appearing in research literature that holds no UK authorisation for human use in any indication.

Source: Freedom of Information response 24/274 — side effect reports for melanotan II products (opens gov.uk in a new tab) (Medicines and Healthcare products Regulatory Agency)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

The published harms literature includes reports of eruptive and atypical melanocytic naevi, melanoma, systemic toxicity with rhabdomyolysis, renal infarction and priapism, alongside a 2025 report of oral mucosal malignant melanoma following nasal spray use. These are individual case reports and cannot establish causation or frequency, but the melanocytic findings are mechanistically coherent given the receptor involved, and the MHRA advises those who have used these products to stop immediately. The unregulated supply chain compounds this: composition, purity and sterility are unverified.

References