Melanocortin receptor agonist
Melanotan II
ClinicalAlso known as MT-II
The tanning-and-libido peptide that never made it to approval.
- Cited sources
- 2
- Human-tested claims
- 2 of 2
- Best evidence
- Tier 2 · Clinical
- Status
- Research-only
A broad-spectrum melanocortin agonist studied for pigmentation and sexual function. Its mechanism is well characterized, but it has no regulatory approval and carries documented safety concerns from unregulated use — a frontier compound with real caveats.
How it works
Melanotan II is a potent full agonist across MC1R, MC3R, MC4R, and MC5R. MC1R activation drives melanin production (tanning); MC3R/MC4R activity affects appetite and sexual response. That receptor breadth — especially MC1R — is what separates it from the central-MC4R-weighted bremelanotide.
Sequence: Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-NH₂A cyclic lactam heptapeptide; identical to bremelanotide except for a C-terminal amide (vs free acid).
What it's studied for
One claim per card, each with its own tier and source. Tiers 1 and 2 are human data. Tiers 3 and 4 are not yet.
- [1]Dorr et al., 1996 (Life Sci, Phase I)(opens in a new tab)
A broad-spectrum α-MSH analog and potent agonist at MC1R/MC3R/MC4R, driving pigmentation and sexual response (early human Phase I).
Clinical - [2]Case report: MT-II toxicity and rhabdomyolysis (PubMed)(opens in a new tab)
Systemic toxicity including rhabdomyolysis and renal dysfunction has been reported after injection.
Clinical
Safety & limitations
Documented adverse events from unregulated use include rhabdomyolysis with renal dysfunction, priapism, and darkening or atypia of moles, with case reports of melanoma. These are case-report grade — real signals, not established frequencies — compounded by contamination risk from unlicensed supply.
[2]Case report: MT-II toxicity and rhabdomyolysis (PubMed)(opens in a new tab)Regulatory & legal status
No regulatory approval for human use in any major jurisdiction; sold only as an unlicensed grey-market injectable. Only early Phase I and small pigmentation studies were ever conducted.
[1]Dorr et al., 1996 (Life Sci, Phase I)(opens in a new tab)Frequently asked
Is Melanotan II safe for tanning?
It is unapproved, and case reports link it to serious harms — rhabdomyolysis, priapism, and changes to moles including melanoma. Dermatologists caution against it.
References
Written by Twenty Residues editorial. Medical review: pending; a named reviewer is being assigned.
Last updated September 19, 2026.
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Update history
- 2026-09-19 — Sourced review — every claim checked against primary literature; sequence, regulatory status, safety, and FAQs added.