What is melanotan II?
Melanotan II (also written melanotan 2, MT-II or MT2) is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (α-MSH): Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge between Asp and Lys and a C-terminal amide (PubChem CID 92432). The compound was first reported in a 1989 design study of cyclic lactam α-MSH(4-10) analogs (Al-Obeidi et al., 1989) and acts as a nonselective melanocortin receptor agonist (Wessells et al., 2000).
Melanotan II has not been approved as a medicine (Deville and Charlier, 2024), and multiple national health organizations have issued safety warnings about the unregulated use of melanotan I and II (Habbema et al., 2017). Disguised Alpha supplies melanotan II only as a lyophilized research compound for laboratory use. It is not for use in people, and this page makes no claim of any cosmetic or other effect.
Melanotan II reference data
| Property | Value |
|---|---|
| Name | Melanotan II (listed in our catalog as Melanotan 2, MT-2) |
| Aliases | MT-II, Melanotan-II, MTII (PubChem CID 92432) |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, also written acetyl-(Nle4, Asp5, D-Phe7, Lys10)-cyclo-α-MSH(4-10) amide (PubChem CID 92432) |
| Peptide class | α-MSH analog cyclic peptide |
| Molecular formula | C₅₀H₆₉N₁₅O₉ |
| Molecular weight | 1024.18 g/mol |
| CAS number | 121062-08-6 |
| Form | Lyophilized powder |
| Size carried | 10MG |
| Testing | Third-party tested, with the certificate for each lot published on the product page and in the COA portal |
Formula, molecular weight, CAS number and peptide class are from the Compound Information section of the Melanotan 2 product page, and the 10 mg size is the labeled amount shown there; sequence and aliases are from PubChem (CID 92432, which lists 1024.2 g/mol). Confirm identity and measured content against your lot's certificate.
What the research covers
Published work on melanotan II falls into six areas. Each summary below states the model used. The human studies were small early-phase trials published between 1996 and 2000, not studies of the research material sold here.
Design and receptor pharmacology
In the 1989 study, the Asp5 to Lys10 lactam analog that corresponds to MT-II was about 90 times as potent as α-MSH in a lizard skin bioassay, and analogs with this 23-membered ring showed prolonged activity, while larger or smaller rings reduced potency (Al-Obeidi et al., 1989).
On cells expressing human MC1, MC3, MC4 and MC5 receptors, MT-II and the related lactam SHU9119 bound with higher overall affinity than cyclic disulfide analogs, and replacing D-Phe7 with D-Nal(2')7 shifted selectivity toward MC4 (Schiöth et al., 1997). An alanine scan at human MC3, MC4 and MC5 receptors found that replacing His left affinity and potency largely unchanged, replacing Arg cut potency about 100-fold and replacing D-Phe or Trp abolished activity at micromolar concentrations (Bednarek et al., 1999).
Feeding, energy balance and stress models in rodents
In mice, intracerebroventricular MT-II inhibited feeding in four models of hyperphagia, including fasted, ob/ob and A(Y) mice, and the melanocortin antagonist SHU9119 blocked the effect. SHU9119 alone increased nocturnal and fast-induced feeding, which the authors took as evidence that melanocortin neurons tonically inhibit feeding (Fan et al., 1997). In male rats under chronic unpredictable stress, MT-II, tested alongside Semax, reversed or attenuated anhedonia, suppression of body-weight gain, adrenal hypertrophy and the fall in hippocampal BDNF (Inozemtseva et al., 2024).
Sexual behavior models in rats
In anesthetized rats, MT-II given systemically or into the paraventricular nucleus of the hypothalamus elicited erectile events and shortened their latency, and systemic administration enhanced erectile responses to cavernous nerve stimulation, an effect abolished by removing the lumbar paravertebral sympathetic chain (Giuliano et al., 2006). In ovariectomized female rats primed with estradiol and progesterone, MT-II increased hops and darts and ear wiggling without changing pacing or lordosis, and it had no effect in rats primed with estradiol alone (Rössler et al., 2006).
Early clinical studies
A pilot phase 1 study in three healthy men reported mild nausea at most levels tested, somnolence and fatigue in one participant and a stretching and yawning complex that coincided with spontaneous penile erections; two participants showed increased skin pigmentation measured by reflectance (Dorr et al., 1996).
In a placebo-controlled crossover study of ten men with psychogenic erectile dysfunction, eight developed erections after MT-II, with nausea, stretching, yawning and decreased appetite reported more often than with placebo (Wessells et al., 1998). The same group's review of 20 men with psychogenic or organic erectile dysfunction reported erections in 17 and frequent nausea and yawning (Wessells et al., 2000).
Physicochemical and analytical studies
Preformulation work measured pKa values of 6.54 for histidine and 11.72 for arginine and an octanol partition coefficient of 2.82 at pH 7.35 (Lan et al., 1994). An LC-MS/MS method quantified MT-II in mouse plasma and brain down to 0.5 ng/mL and 2.5 ng/g and showed rapid plasma clearance with low brain penetration (Hatziieremia et al., 2007).
LC-UV-MS/MS testing of vials bought online found 4.32 to 8.84 mg of peptide against a 10 mg label (Breindahl et al., 2015). High-resolution mass spectrometry has also characterized melanotan II and bremelanotide in confiscated samples (Mestria et al., 2021).
Safety reports and regulatory warnings
A 2017 dermatology review of unregulated melanotan use summarized case reports of changes in existing moles, newly emerging dysplastic nevi and four melanomas arising during or shortly after use, noted that conclusive evidence of a causal link is lacking, and reported that multiple national health organizations have issued safety warnings (Habbema et al., 2017). Case reports describe a melanoma that coincided with melanotan II use (Hjuler and Lorentzen, 2014) and a renal infarction the authors attributed most likely to it (Peters et al., 2020).
Key studies
- Al-Obeidi F, et al. "Potent and prolonged acting cyclic lactam analogues of alpha-melanotropin: design based on molecular dynamics." J Med Chem. 1989. PMID 2555512. DOI 10.1021/jm00132a010. Peptide design: cyclic lactam α-MSH analogs in frog and lizard skin bioassays.
- Dorr RT, et al. "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study." Life Sci. 1996. PMID 8637402. DOI 10.1016/0024-3205(96)00160-9. Pilot phase 1 study in three healthy men: adverse events and skin reflectance.
- Fan W, et al. "Role of melanocortinergic neurons in feeding and the agouti obesity syndrome." Nature. 1997. PMID 8990120. DOI 10.1038/385165a0. Mouse hyperphagia models: feeding with MT-II and the antagonist SHU9119.
- Schiöth HB, et al. "Selectivity of cyclic [D-Nal7] and [D-Phe7] substituted MSH analogues for the melanocortin receptor subtypes." Peptides. 1997. PMID 9357059. DOI 10.1016/s0196-9781(97)00079-x. Cell-based binding at human MC1, MC3, MC4 and MC5 receptors.
- Bednarek MA, et al. "Structure-function studies on the cyclic peptide MT-II, lactam derivative of alpha-melanotropin." Peptides. 1999. PMID 10447101. DOI 10.1016/s0196-9781(99)00048-0. Alanine scan and NMR at human MC3, MC4 and MC5 receptors.
- Wessells H, et al. "Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II." Int J Impot Res. 2000. PMID 11035391. DOI 10.1038/sj.ijir.3900582. Placebo-controlled crossover studies in 20 men with erectile dysfunction.
- Giuliano F, et al. "Melanotan-II: Investigation of the inducer and facilitator effects on penile erection in anaesthetized rat." Neuroscience. 2006. PMID 16360286. DOI 10.1016/j.neuroscience.2005.11.008. Anesthetized rats: central and peripheral sites of erectile responses.
- Habbema L, et al. "Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review." Int J Dermatol. 2017. PMID 28266027. DOI 10.1111/ijd.13585. Review of case reports and national safety warnings.
Handling and storage of lyophilized melanotan II
General laboratory practice for this material:
- Store the lyophilized powder at -20°C, protected from light, until use (storage guidance on the product page).
- Let the sealed vial reach room temperature before opening so moisture does not condense on the powder.
- The sequence contains tryptophan and histidine, both prone to oxidation and photodegradation, so limit exposure to air, light and oxidizers.
- The histidine pKa of 6.54 (Lan et al., 1994) means the peptide's charge shifts near neutral pH, which affects buffer choice and chromatography.
- For mass spectrometric identity checks, use the doubly charged ion at m/z 513 (Breindahl et al., 2015); methods capped near 1000 Da can miss the singly charged ion (Deville and Charlier, 2024).
- After reconstitution, keep solutions at 2 to 8°C and protected from light, and split stock into single-use aliquots to avoid freeze/thaw cycles.
- Record the lot number and keep its certificate with your notes. For quantitative work, use the measured content on the certificate rather than the label mass.
Frequently asked questions
What is melanotan II?
Melanotan II is a cyclic, lactam-bridged α-MSH(4-10) analog (PubChem CID 92432) that binds human MC1, MC3, MC4 and MC5 receptors (Schiöth et al., 1997) and is studied in rodent feeding and behavior models and analytical chemistry.
Are melanotan 2, MT-II and the MT2 peptide the same compound?
Yes. They are names for the same molecule, C₅₀H₆₉N₁₅O₉, CAS 121062-08-6. Melanotan I is a different compound, a linear peptide (Hadley and Dorr, 2006) that our product page lists as C₇₈H₁₁₁N₂₁O₁₉, 1646.8 g/mol.
How does melanotan II differ from PT-141?
PT-141 (bremelanotide) was developed as an analog of melanotan II (Hadley and Dorr, 2006). Both share the cyclic core, but PT-141 ends in a free carboxylic acid instead of an amide (C₅₀H₆₈N₁₄O₁₀, PubChem CID 9941379). See our PT-141 research guide.
Why have health agencies warned about melanotan products?
The warnings concern unregulated products sold for cosmetic use (Habbema et al., 2017), which testing has found below label content and carrying unidentified impurities (Breindahl et al., 2015). Our material is supplied for laboratory research only.
How should melanotan II powder be stored?
Keep the lyophilized powder at -20°C and protected from light. After reconstitution, store the solution at 2 to 8°C, protected from light, and avoid freeze/thaw cycles, as listed on the product page.
Where can researchers buy melanotan II?
Disguised Alpha sells it for laboratory research, third-party tested with the certificate published on the product page: Melanotan 2 (10MG).
Related compounds and guides
- PT-141 and its research guide
- Melanotan 1 and its research guide
- Semax research guide: Semax was tested alongside MT-II in a rat chronic stress study
- COA portal: every published certificate, by lot
This product is for research use only. It has not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.