Educational reference. Research use only.
Melanotan II: Mechanism, Research, and Regulatory Status
Melanotan II is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone, CAS 121062-08-6, molecular weight 1024.18 Da, that acts as a non-selective melanocortin receptor agonist. Human data on Melanotan II are limited to small early studies: one 3-subject Phase 1 pilot (1996) and two crossover studies in men. Melanotan II is not approved for human use.
Last reviewed 2026-09-29
What is Melanotan II?
Melanotan II key facts
Melanotan II, also written MT-II, is a synthetic cyclic heptapeptide with the sequence Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, CAS number 121062-08-6 and a molecular weight of 1024.18 Da. Melanotan II is an analog of alpha-melanocyte-stimulating hormone and acts as a non-selective agonist at melanocortin receptors MC1R through MC5R; MC1R activation drives melanin production, and MC4R activation is linked to appetite and sexual function. In a 1996 Phase 1 pilot study in Life Sciences, Dorr and colleagues reported increased skin pigmentation in two of three subjects, along with nausea, somnolence and spontaneous erections. Wessells and colleagues reported erectile responses in men with psychogenic (1998) and organic (2000) erectile dysfunction in small crossover studies. Langan and colleagues reviewed reports of changing melanocytic nevi in the British Journal of Dermatology in 2010. Melanotan II is distinct from afamelanotide, a linear alpha-MSH analog. Melanotan II is not approved by the FDA or any regulator, is prohibited by WADA under S2, and is supplied for research use only.
How does Melanotan II work?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide (a seven-amino-acid ring) analog of alpha-melanocyte-stimulating hormone (α-MSH). It acts as a non-selective agonist at melanocortin receptors MC1R through MC5R. MC1R activation drives melanogenesis, the production of the skin pigment melanin.
MC4R activation modulates appetite and sexual function.
What has research on Melanotan II found?
What published peer-reviewed research and preclinical studies have established about Melanotan II:
- 01Synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (α-MSH)
- 02Acts as a non-selective agonist at melanocortin receptors MC1R through MC5R
- 03Clinical research has explored melanogenesis (tanning response) and sexual dysfunction applications
- 04Bremelanotide (PT-141), an active metabolite, received FDA approval for hypoactive sexual desire disorder
- 05Preclinical models suggest modulation of appetite, energy homeostasis, and inflammatory responses via MC4R
- 06Two controlled crossover studies in men reported erectile responses in psychogenic (Wessells 1998) and organic (Wessells 2000) erectile dysfunction. This is the MC4R signal that bremelanotide was later designed around
- 07Distinct from afamelanotide (Scenesse), a LINEAR alpha-MSH analog approved for erythropoietic protoporphyria. The two are routinely conflated, but they differ in structure, receptor selectivity and regulatory status
- 08Dermatology literature documents darkening and proliferation of melanocytic nevi during use, and reviews have raised melanoma concerns given MC1R agonism on melanocytes (Langan 2010)
Which studies have examined Melanotan II?
Phase 1 pilot study: melanogenesis and sexual function
Phase 1 · 1996Increased facial and upper-body pigmentation in two of three subjects; intermittent spontaneous penile erections during the study; mild nausea at most exposure levels and grade II somnolence and fatigue at the highest exposure level in one subject
Frequently asked questions about Melanotan II
Is Melanotan II legal?+
Melanotan II is not approved as a pharmaceutical in any jurisdiction and is classified as WADA S2 prohibited. Multiple regulatory agencies including the FDA, EMA, and TGA have issued warnings about unlicensed use. For research purposes only.
How does Melanotan II relate to bremelanotide (Vyleesi)?+
Bremelanotide (PT-141) is derived from Melanotan II research and is a selective MC4R agonist that received FDA approval for hypoactive sexual desire disorder (HSDD) in 2019. Unlike Melanotan II, bremelanotide was redesigned for selective MC3R/MC4R activity with reduced MC1R activity to minimize tanning effects.
What is the difference between Melanotan II, Melanotan I and afamelanotide?+
Melanotan I and afamelanotide are the same molecule under two names: a linear alpha-MSH analog marketed as Scenesse and approved in the US and EU for erythropoietic protoporphyria. Melanotan II is a different compound entirely, a cyclic heptapeptide with broad non-selective activity across MC1R through MC5R, and it is approved nowhere. The three names are used interchangeably in casual discussion, which is wrong and matters: only one has an approved indication and a controlled safety dataset.
Why does Melanotan II cause nausea so consistently?+
Nausea is the dose-limiting effect across the human literature, reported in roughly half of subjects at the higher exposure levels in the original Phase 1 work. It is attributed to central melanocortin activity rather than a peripheral effect, which is why it is dose-dependent.
What is known about the effect on moles and melanoma risk?+
This is the most serious open question. MC1R agonism acts directly on melanocytes, and dermatology case reports and reviews document darkening, enlargement and eruptive appearance of nevi during use. A causal link to melanoma has not been established, but it also has not been excluded, and the mechanism gives a plausible route. Reviews in the dermatological literature (Langan 2010) treat it as an unresolved safety concern rather than a theoretical one.
Why is Melanotan II so widely available if it is not approved anywhere?+
It has never completed a development program, so no regulator has assessed it for safety or efficacy, and it is sold outside the pharmaceutical supply chain entirely. The FDA, EMA and TGA have all issued consumer warnings about unlicensed melanotan products. That absence of oversight also means composition and purity vary between suppliers, which is precisely why batch-level analytical documentation matters for research material.
Does the tanning effect require UV exposure?+
Melanogenesis is stimulated directly through MC1R rather than requiring UV, which is the pharmacological basis of the compound. This is often presented as making it a safer alternative to sun exposure, a claim the published literature does not support: it removes the UV stimulus but adds an unapproved systemic peptide with a documented adverse-effect profile.
References & sources
Every citation below was resolved against its primary source before publication. Each PMID was checked against its PubMed record and each DOI through doi.org. Follow any link to read the paper at the publisher rather than taking our summary on trust.
- [1]Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sciences. 1996. PMID: 8637402 DOI: 10.1016/0024-3205(96)00160-9
- [2]King SH, Mayorov AV, Balse-Srinivasan P, et al. Melanocortin receptors, melanotropic peptides and penile erection. Current Topics in Medicinal Chemistry. 2007. PMID: 17584130
- [3]Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006. PMID: 16412534 DOI: 10.1016/j.peptides.2005.01.029
- [4]Wessells H, Fuciarelli K, Hansen J, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. The Journal of Urology. 1998. PMID: 9679884
- [5]Wessells H, Gralnek D, Dorr R, et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology. 2000. PMID: 11018622 DOI: 10.1016/s0090-4295(00)00680-4
- [6]Langan EA, Nie Z, Rhodes LE. Melanotropic peptides: more than just 'Barbie drugs' and 'sun-tan jabs'?. British Journal of Dermatology. 2010. PMID: 20545686 DOI: 10.1111/j.1365-2133.2010.09891.x
Where this data comes from
- Citations & trial data: PubMed (NCBI, U.S. National Library of Medicine), Crossref and ClinicalTrials.gov.
- Chemical identity: PubChem and UniProt. Where sources conflicted, the disputed value is omitted rather than guessed.
- Regulatory status: U.S. FDA publications and, where applicable, the WADA Prohibited List. Compounding status changes often, so check FDA directly before relying on it.
- Purity, form and storage are handling and supplier conventions, not literature-derived values. Confirm against the lot-specific certificate of analysis. General handling is covered in the storage and stability guide.
Content last reviewed 2026-09-29. Compiled by Veridian Research from the primary literature. This page is an educational reference for laboratory researchers. It is not medical advice, and it describes no human use.
Is Melanotan II approved for human use?
Melanotan II is an investigational compound not approved by the FDA or any regulatory agency for therapeutic use. WADA has classified Melanotan II as a prohibited substance (S2). Regulatory agencies in multiple countries have issued warnings about unregulated use. For research purposes only.
Research-use-only material
Specifications and certificate of analysis
Melanotan II is stocked as a research reagent. The most recent batch (6) was analysed by Janoshik Analytical at 99.257% purity; the signed certificate is published in full.