Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.
A 1980s University of Arizona tanning peptide that never got a licence, acquired a black market, and is documented mainly through case reports of harm.
Also known as: MT-2 · MT-II · Melanotan 2 · MT2 · Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Part of the Cosmetic & skin peptides cluster
Overview
Melanotan II is a synthetic cyclic heptapeptide analogue of α-melanocyte-stimulating hormone (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) that non-selectively activates melanocortin receptors, producing skin darkening through MC1R and erections and appetite effects through MC4R. It has never been approved anywhere and is sold unlawfully online for tanning; the published human literature consists largely of case reports of rhabdomyolysis, renal infarction and melanoma coinciding with its use. A phase 2 trial as an adjunct to phototherapy was registered in 2026.
Source & context
Biological / chemical source: Synthetic cyclic peptide
Primary research or clinical context: Not approved in any jurisdiction; sold unlawfully online as a tanning injectable. One phase 2 trial registered (2026) as an adjunct to phototherapy
What Melanotan II is
Melanotan II (MT-II) is a synthetic cyclic peptide analogue of α-melanocyte-stimulating hormone, designed in the 1980s at the University of Arizona as a candidate sunless-tanning agent. Seven residues — norleucine, then a ring of Asp-His-D-Phe-Arg-Trp-Lys closed by a lactam bridge — reproduce the His-Phe-Arg-Trp core that every melanocortin receptor recognises, in a form far more potent and stable than the hormone. Formula C50H69N15O9, average mass about 1,024 Da. It was never licensed. Its C-terminal amide is the only difference from bremelanotide, which was later approved for a different indication; MT-II itself survives as an unlicensed injectable sold online for tanning.
Sequence and chemistry
The IUPHAR one-letter representation is XDHFRWK, where X is norleucine; the display cannot show the D-configuration of the phenylalanine or the ring closure between the aspartate and lysine side chains, both of which are what make the molecule work. Norleucine replaces α-MSH's methionine to remove an oxidation site; D-Phe at position 4 and the lactam constraint hold the pharmacophore in its active shape and protect it from peptidases. Medicinal-chemistry work continues on this scaffold — Tomassi et al. (Journal of Medicinal Chemistry 2022) used it to generate functionally selective melanocortin agonists — because the α-MSH core remains the template for the whole receptor family.
Mechanism and effects
MT-II activates melanocortin receptors without selectivity. At MC1R on melanocytes it increases eumelanin synthesis, hence skin darkening even without sun; at MC4R in the hypothalamus it triggers erections and suppresses appetite — in anaesthetised rats, intravenous or intra-hypothalamic MT-II dose-dependently induced erectile events (Giuliano et al., Neuroscience 2006). Rodent studies have explored other central effects: reversal of memory impairment after a high-fat diet (Wekwejt et al., Biomedicine & Pharmacotherapy 2023) and of autism-like behaviours in a maternal-immune-activation mouse model (Minakova et al., PLoS One 2019). These are laboratory findings with the peptide as a tool compound, not evidence for any human use.
Human evidence: case reports of harm
Because MT-II was never developed through trials, the human literature is dominated by adverse-event reports. A 39-year-old man who injected 6 mg — six times what he understood to be the starting dose — developed sympathomimetic toxicity and rhabdomyolysis with creatine kinase peaking at 17,773 IU/L and acute kidney injury, requiring intensive care (Nelson et al., Clinical Toxicology 2012). A 20-year-old woman with skin type II developed cutaneous melanoma three months after a course of self-injected MT-II combined with sunbed use (Hjuler et al., Dermatology 2014). Renal infarction attributed to MT-II has been reported, with thrombotic and direct toxic mechanisms proposed (Peters et al., CEN Case Reports 2020). Case reports cannot establish causation, but they define the risk profile that no trial ever measured.
| Report | Event | Context |
|---|---|---|
| Nelson et al. 2012 | Rhabdomyolysis, tachycardia, kidney injury | 6 mg self-injection, internet-sourced |
| Hjuler et al. 2014 | Cutaneous melanoma | 3–4 week course plus sunbeds, skin type II |
| Peters et al. 2020 | Renal infarction | Review plus case; thrombotic mechanism proposed |
How it is actually used
A qualitative study of UK and Irish online forums (Gilhooley et al., Dermatology 2021) extracted 623 discussion entries from 205 participants and found motivations centred on a tanned appearance before holidays and for fitness or bodybuilding, alongside widespread misinformation about an unregulated product, improvised preparation and dosing, sunbed use, and side effects. The covert nature of use means prevalence is unknown. Health authorities in several countries have issued warnings against injecting melanotan products bought online.
Regulatory status and a single trial
Melanotan II is not approved in any jurisdiction and cannot be lawfully sold for human use in the US, Canada or the EU. Its related compound afamelanotide (Melanotan I), a linear analogue, is an approved implant for a rare photosensitivity disorder, which is why the two names are often confused; the melanotan comparison guide separates them. In 2026 a phase 2 trial was registered (NCT07437560) testing MT-II as an adjunct to narrow-band UVB phototherapy for repigmentation, listed as recruiting — the first controlled human study of the molecule in decades.
What this page is not
It is an educational profile of a research peptide with a documented harm record and no approval. It does not describe how to obtain, prepare or use anything, and it is not medical advice.
Sequence
One-letter sequence commonly cited for Melanotan II (educational; isoforms and modifications may differ):
XDHFRWK
X = norleucine (Nle), a non-canonical residue; the D-Phe at position 4 and the Asp–Lys lactam bridge that closes the ring are not shown in one-letter code. X marks a non-canonical residue — see the structure block below. (Plotted as alanine on the wheel.)
Residues plotted ~100° apart around an α-helix — clustering of one color reveals an amphipathic face.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — a cyclic lactam-bridged analogue of the α-MSH core sequence His-Phe-Arg-Trp
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Amide (the des-amide form is bremelanotide)
Average reference mass
Reference policy updated: 2026-10-05
- IUPHAR/BPS source snapshot · 2026-10-01
- PubChem molecular record · 2026-10-01
- Molecular formula
- C50H69N15O9
- Average reference mass
- ≈ 1,024.2
- Receptors
- Non-selective melanocortin agonist: MC1R (pigmentation), MC3R and MC4R (sexual function, appetite), MC5R
- Backbone
- Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — a cyclic lactam-bridged analogue of the α-MSH core sequence His-Phe-Arg-Trp
- C-terminus
- Amide (the des-amide form is bremelanotide)
- Status
- Not approved in any jurisdiction as of September 2026; one phase 2 trial registered (NCT07437560)
Nle1 replaces the oxidisable Met of α-MSH; D-Phe4 and the side-chain lactam cyclisation between Asp and Lys lock the receptor-binding conformation and resist proteolysis; N-acetyl and C-amide cap the termini.
- PubChem CID: 92432
- IUPHAR ligand: 1323
- ChEMBL: CHEMBL430239
- CAS RN: 121062-08-6
- UNII: UPF5CJ93X7
Chemistry values: curated profile, PubChem, IUPHAR/BPS Guide to Pharmacology · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 1 registered study with “Melanotan II” as an intervention (snapshot 2026-09-06). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT07437560 | Melanotan II (MT-II) as an Adjunct to NB-UVB Phototherapy for Repigmentation in Stable Nonsegmental Vitiligo | Phase 2 | recruiting | 2026-02-27 |
Melanotan II — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — a cyclic lactam-bridged analogue of the α-MSH core sequence His-Phe-Arg-TrpAverage reference mass: 1,024.2 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
Change log
Dated observations from the data pipeline (registry flags, trial footprints, identifiers) and editorial reviews of this profile.
- EditorialProfile content reviewed and updated by the editorial team.
FAQ about Melanotan II
What is Melanotan II?+
Melanotan II is a synthetic cyclic heptapeptide analogue of α-melanocyte-stimulating hormone (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) that non-selectively activates melanocortin receptors, producing skin darkening through MC1R and erections and appetite effects through MC4R. It has never been approved anywhere and is sold unlawfully online for tanning; the published human literature consists largely of case reports of rhabdomyolysis, renal infarction and melanoma coinciding with its use. A phase 2 trial as an adjunct to phototherapy was registered in 2026.
What Canadian product status is recorded for Melanotan II?+
Canadian product status for Melanotan II has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the typical length of Melanotan II?+
Melanotan II is commonly described as approximately 7 amino acids (Cyclic melanocortin-receptor agonist (unlicensed research peptide)).
What is Melanotan II?+
A synthetic cyclic analogue of α-MSH that activates melanocortin receptors non-selectively, causing skin darkening (MC1R) and erections and appetite changes (MC4R). It was never approved.
Is Melanotan II safe?+
Unknown — it was never tested in trials. The human literature is case reports: rhabdomyolysis and kidney injury after a 6 mg injection, melanoma coinciding with use plus sunbeds, and renal infarction.
Is Melanotan II legal or approved?+
It is not approved anywhere and cannot lawfully be sold for human use in the US, Canada or the EU. A phase 2 phototherapy-adjunct trial was registered in 2026.
What is the difference between Melanotan II and PT-141?+
One terminal group: MT-II is the C-terminal amide, bremelanotide (PT-141) the free acid. Bremelanotide is an approved medicine for a sexual-desire indication; MT-II is unlicensed.
What is the difference between Melanotan I and II?+
Melanotan I (afamelanotide) is a linear α-MSH analogue approved as an implant for a rare photosensitivity disorder; Melanotan II is a cyclic, non-selective analogue with no approval.
What is the sequence of Melanotan II?+
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2; formula C50H69N15O9, mass about 1,024 Da.
Further reading
- ComparisonMelanotan I vs Melanotan II: An Educational ComparisonAn educational comparison of two melanocortin peptides—receptor selectivity (MC1R vs MC1R and MC4R), afamelanotide's narrow approval, and the unapproved status of research use.
- SafetyPeptide Safety and Risks: A Balanced Educational OverviewAn objective, balanced overview of what research does and does not establish about peptide risks—unknowns, purity and contamination concerns, and why unapproved compounds carry uncertainty. Not reassurance and not medical advice.
- FoundationsWhat Are Research Peptides? A Clear Educational GuideLearn what “research peptides” means, how they differ from approved peptide drugs, quality markers (COA, purity), and how to study them responsibly.
- CanadaAre Peptides Legal in Canada? A Regulatory GuideAn educational overview of how Health Canada regulates peptides—drug authorization, DINs, the “research use only” gray area, and import ambiguity. Not legal advice.
Related peptides
References & further reading
- 1.Todorovic et al. (2024). 5-Hydroxypyrroloindoline Affords Tryptathionine and 2,2'-bis-Indole Peptide Staples: Application to Melanotan-II. Chemistry
- 2.Wekwejt et al. (2023). Melanotan-II reverses memory impairment induced by a short-term HF diet. Biomed Pharmacother
- 3.Nelson et al. (2012). Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol (Phila)
- 4.Gilhooley et al. (2021). Melanotan II User Experience: A Qualitative Study of Online Discussion Forums. Dermatology
- 5.Tomassi et al. (2022). CLIPSing Melanotan-II to Discover Multiple Functionally Selective hMCR Agonists. J Med Chem
- 6.Peters et al. (2020). Melanotan II: a possible cause of renal infarction: review of the literature and case report. CEN Case Rep
- 7.Hjuler et al. (2014). Melanoma associated with the use of melanotan-II. Dermatology
- 8.Devlin et al. (2013). Melanotan II overdose associated with priapism. Clin Toxicol (Phila)
- 9.Giuliano et al. (2006). Melanotan-II: Investigation of the inducer and facilitator effects on penile erection in anaesthetized rat. Neuroscience
- 10.Minakova et al. (2019). Melanotan-II reverses autistic features in a maternal immune activation mouse model of autism. PLoS One
- 11.PubChem — Melanotan II (CID 92432)