All information below describes the compound's chemical identity, laboratory handling, and the published research literature. It describes molecular targets and results in laboratory and animal models only — not effects in humans — and is not evidence of any human benefit.
What Is Melanotan II?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH), with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. It was designed in the late 1980s at the University of Arizona through cyclization of the melanotropin core, incorporating a lactam bridge, a norleucine substitution, and a D-phenylalanine residue. It does not occur freely in nature; it is a synthetic analogue characterized by resistance to enzymatic degradation relative to the linear native peptide, a physicochemical property that has made it a common subject of preclinical laboratory investigation.
It is supplied as a reference compound for in vitro and animal research use only. The sections below summarize its chemical identity, laboratory handling, the molecular targets and model systems examined in the published literature, and the primary references — without describing outcomes, efficacy, or effects in humans.
Research Targets & Pathways
Published preclinical literature has examined Melanotan II in relation to the melanocortin receptor family. These are pathway associations reported in laboratory and animal models; refer to the cited studies for methods and findings.
- Melanocortin-1 receptor (MC1R) — examined in melanocyte and melanoma cell-line assay systems relating to pigmentation biology.
- Melanocortin-3 receptor (MC3R) — studied in central-nervous-system model systems relating to energy homeostasis.
- Melanocortin-4 receptor (MC4R) — investigated in hypothalamic feeding-behavior and neuroendocrine model systems.
- Melanocortin-5 receptor (MC5R) — characterized in receptor-binding and exocrine-tissue assay systems.
- cAMP / adenylyl cyclase signaling — the second-messenger readout used to characterize melanocortin-receptor agonism; MT-II does not appreciably engage the MC2R (ACTH) receptor.
Model Systems Studied
Melanotan II has been used as a test compound across a range of published preclinical model systems, primarily in rodents and in vitro cell assays. Refer to the cited literature for study designs, endpoints, and findings.
- Pigmentation — B16 melanoma and human melanocyte cultures; melanogenesis and tyrosinase-activity assay systems.
- Energy balance — hypothalamic and nucleus-accumbens microinjection models; MC4R-knockout mouse models.
- Neuroendocrine — central pro-erectile pathway models in rat spinal and supraspinal preparations.
- Receptor pharmacology — HEK-293 and cloned-receptor systems for binding-affinity and cAMP-accumulation profiling.
- Early human characterization — small controlled studies measuring receptor-linked responses under monitored conditions.
Note: much of the human-facing literature consists of small early-phase characterization studies and case reports of unregulated self-administration; controlled clinical data are limited.
Stability & Handling
Melanotan II is noted in the literature for resistance to enzymatic degradation relative to the linear native α-MSH peptide, a property attributed to its cyclic lactam design and non-natural residue substitutions. The lyophilized peptide is hygroscopic and light-sensitive; handling under desiccated, low-light conditions and minimizing freeze–thaw cycling are standard practices for preserving structural integrity in research settings. Values below are general laboratory guidance and should be confirmed against the lot-specific Certificate of Analysis.
Molecular & Technical Profile
C50H69N15O9 | MW ~1024.18 g/mol | CAS 121062-08-6 | Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Storage, Reconstitution & Working Concentrations
Storage, reconstitution, and working-concentration values are general laboratory guidance for in vitro and animal research; always confirm against the lot-specific Certificate of Analysis. The molecular weight is reported as approximately 1024.18 g/mol (monoisotopic and average values differ by convention).
Current Research Status
As of the time of this writing, Melanotan II has not been approved by the U.S. Food and Drug Administration (FDA) for any human use. The available evidence base is primarily preclinical, derived from rodent and in vitro models, alongside small early-phase human characterization studies and published case reports of unregulated self-administration. It is worth distinguishing Melanotan II from structurally related melanocortin-receptor agonists that have reached regulatory approval as distinct, separately manufactured drug products — for example afamelanotide (marketed as Scenesse), setmelanotide (marketed as Imcivree), and bremelanotide (marketed as Vyleesi). The material supplied here is research-grade Melanotan II for laboratory use only; it is not any of those approved drug products and is not supplied for human use. Ongoing research continues to characterize the compound's receptor-binding profile and identify which experimental findings may have translational relevance.
Research FAQ
Is Melanotan II approved for human use?
No. Melanotan II has not been approved by the FDA for any human use. The evidence base is largely preclinical (rodent and in vitro models) with limited early human characterization studies, and the compound is supplied for laboratory research use only — not for human consumption.
What is Melanotan II's molecular formula and sequence?
A synthetic cyclic heptapeptide, sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — molecular formula C50H69N15O9, MW approximately 1024.18 g/mol, CAS 121062-08-6.
How is Melanotan II stored and reconstituted?
Store lyophilized at −20°C, desiccated and protected from light. Reconstitute in sterile or bacteriostatic water; store the reconstituted solution at 2–8°C for up to ~28 days and avoid repeated freeze–thaw.
What receptors has Melanotan II been studied for?
Preclinical work has characterized it as a non-selective agonist across the MC1R, MC3R, MC4R, and MC5R melanocortin receptors (with minimal MC2R engagement), examined in pigmentation, energy-balance, and neuroendocrine model systems via receptor-binding and cAMP-accumulation assays.
Selected References
- Dorr RT, et al. (1996). Evaluation and characterization of the melanotropic peptide Melanotan II for receptor binding and pigmentary response. Journal of Investigative Dermatology / Life Sciences.
- Hadley ME, et al. (1996). Melanotan-II and melanocortin receptor pharmacology characterized in rodent models. Life Sciences.
- Mountjoy KG, et al. Melanocortin receptor subtypes (MC1R–MC5R) cloned and characterized for ligand selectivity and tissue distribution. Biochemical Journal.
- Wikberg JES, et al. (2000). Melanocortin receptor pharmacology reviewed across receptor subtypes with structure–activity relationship data. Pharmacological Research.
- Wessells H, et al. (2000). Melanotan-II characterized for melanocortin receptor–linked responses under monitored conditions in men. Journal of Urology.
- Giuliano F, et al. (2002). Melanocortin receptor involvement in central pathways characterized in rat spinal and supraspinal models. Neuroscience.