Melanotan II (MT-II) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (alpha-MSH). It corresponds to alpha-MSH residues 4 to 10 with norleucine in place of methionin...
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (alpha-MSH). It corresponds to alpha-MSH residues 4 to 10 with norleucine in place of methionine, D-phenylalanine in place of L-phenylalanine, an acetylated N-terminus, an amidated C-terminus and a lactam bridge closing the ring.[2] PubChem lists it as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, C50H69N15O9, 1024.2 g/mol, CAS 121062-08-6.[1] Pepitiva supplies Melanotan II as a lyophilized powder (10 mg vials, ≥98% purity) for in vitro and preclinical research.
Regulatory status
Melanotan II is not approved as a medicine by the FDA or any other regulator; forensic and clinical authors describe it as unlicensed and kept off the market because of safety concerns.[8][14] The FDA has noted that compounded Melanotan II may pose a risk of immunogenicity and that published case reports describe serious adverse events, including melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism.[9]
Not the same as afamelanotide
Afamelanotide, also called melanotan I or [Nle4, D-Phe7]-alpha-MSH, is a different molecule: a linear 13-residue peptide of 1646.8 g/mol.[10] It was tested in randomized trials in erythropoietic protoporphyria and was approved by the FDA in 2019 as a subcutaneous implant.[11][12] That approval does not extend to Melanotan II.
For research use only. Not for human consumption.
Quality & Storage
≥98% purity. Lyophilized Powder. Storage: -20°C. For research purposes only.
Mechanism of Action
Melanocortin receptor pharmacology
Melanotan II is a non-selective agonist of the melanocortin receptors.[6] These five class A G protein-coupled receptors, MC1R to MC5R, take part in pigmentation, steroidogenesis and energy homeostasis, among other functions.[5] A 2024 review lists Melanotan II among the recommended tool compounds of the field, used to validate receptor-expressing cell lines, in cryo-EM structures of receptor complexes and as a reference in drug discovery.[5]
What early human studies observed
Pigmentation (1996): in a pilot Phase I study, Melanotan II produced measurable tanning of the face, upper body and buttocks. The study also recorded nausea, a stretching and yawning complex, and spontaneous penile erections.[2]
Erections (1998): in a placebo-controlled crossover study, 8 of 10 men with psychogenic erectile dysfunction developed clinically apparent erections after Melanotan II; nausea, yawning and decreased appetite were reported more often than with placebo.[3]
These small studies are historical background; the compound was never approved.
Research Applications
From Melanotan II to approved melanocortin drugs
Melanotan I and Melanotan II were designed by Hadley, Dorr and colleagues as enzymatically resistant alpha-MSH analogues and tested clinically for tanning and erectile dysfunction, respectively. Bremelanotide (PT-141) was developed as a Melanotan II analogue.[4] Bremelanotide was approved by the FDA in 2019.[13] See PT-141 (Bremelanotide).
Safety signals from unregulated use
Skin: case reports link unregulated melanotan use with changes in existing moles and new dysplastic nevi, and four reports describe melanomas arising during or shortly after use, although a causal link has not been proven.[7] A review of eruptive melanocytic nevi listed melanotan among the suspected triggers.[15]
Kidney: rhabdomyolysis and renal failure have been described, and a 2020 report attributed a renal infarction to Melanotan II.[6]
Oral mucosa: a 2026 case report documented gingival and buccal pigmentation that persisted three months after injections stopped.[14]
Product quality: a seized vial labeled Melanotan II contained the peptide at a purity of 30%.[8]
Laboratory research applications
Melanocortin receptor assays: non-selective reference agonist across receptor subtypes.
Melanogenesis: pigment production in melanocyte cultures.
Energy balance: central melanocortin signaling in rodent models.
Analytical chemistry: LC-MS identification of the doubly charged peptide.[8]
This product is sold for laboratory research and is not intended for human or veterinary use.
Storage & Handling Guidelines
Proper storage and handling are essential to maintain peptide integrity and ensure reliable research results. All Pepitiva Biolabs peptides are supplied as lyophilized (freeze-dried) powder, which provides excellent long-term stability when stored correctly. Store lyophilized peptides at -20°C for long-term storage or 2-8°C for short-term use. Once reconstituted, peptide solutions should be stored at 2-8°C and used within the timeframe specified in the product documentation. Always use sterile bacteriostatic water for reconstitution and handle peptides in a clean laboratory environment to prevent contamination. Avoid repeated freeze-thaw cycles, as thermal stress can cause peptide degradation and loss of biological activity.
Quality Control & Certification
This product is manufactured under strict quality control protocols and has been verified through comprehensive analytical testing. Each batch undergoes reverse-phase HPLC analysis for purity determination and electrospray ionization mass spectrometry (ESI-MS) for molecular identity confirmation. A detailed Certificate of Analysis (COA) is available for download, documenting purity percentage, molecular weight verification, appearance, and recommended storage conditions. Pepitiva Biolabs maintains batch-level traceability from synthesis through delivery, ensuring complete transparency and quality assurance for your research.
Frequently Asked Questions
What is Melanotan II?
A synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, 1024.2 g/mol) that acts as a non-selective melanocortin receptor agonist.
Is Melanotan II approved by the FDA?
No. Melanotan II is not approved by the FDA or any other regulator. The FDA has cited immunogenicity concerns and published case reports of serious adverse events.
Is Melanotan II the same as afamelanotide?
No. Afamelanotide (melanotan I) is a linear 13-amino-acid peptide (1646.8 g/mol) approved by the FDA in 2019 as an implant. Melanotan II is a smaller cyclic peptide with a different structure and no approval.
What is the difference between Melanotan II and PT-141?
PT-141 (bremelanotide) was developed as an analogue of Melanotan II and was approved by the FDA in 2019; Melanotan II itself was never approved. See PT-141.
What safety concerns have been reported?
Case reports of unregulated use describe changing or new moles, melanoma, kidney injury, priapism and persistent oral pigmentation. These reports do not prove causation, but they are why regulators have issued warnings.
How should Melanotan II be stored?
Keep the lyophilized powder at −20 °C, protected from light and moisture.
Is this product approved for human use?
No. This product is intended exclusively for in vitro scientific research and laboratory use. It is not approved for human or veterinary use, not intended for diagnostic or therapeutic purposes, and should not be administered to humans or animals under any circumstances.
How do I reconstitute this peptide?
Add sterile bacteriostatic water slowly to the vial, directing the stream against the glass wall rather than directly onto the lyophilized powder. Gently swirl the vial until the powder is fully dissolved — do not shake vigorously. The recommended reconstitution volume depends on your desired concentration. Refer to the product documentation for specific guidance.
Can I get a Certificate of Analysis (COA)?
Yes. A Certificate of Analysis is included with every order and is also available for download from the product page. The COA documents HPLC purity, mass spectrometry identity confirmation, batch number, production date, and storage recommendations.
Scientific References
PubChem. Melanotan II, CID 92432: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2; C50H69N15O9, 1024.2 g/mol, CAS 121062-08-6. Source
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 Sci. 1996;58(20):1777-84. PubMed
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. J Urol. 1998;160(2):389-93. PubMed
Weirath NA, Haskell-Luevano C. Recommended Tool Compounds for the Melanocortin Receptor (MCR) G Protein-Coupled Receptors (GPCRs). ACS Pharmacol Transl Sci. 2024;7(9):2706-2724. PubMed
Peters B, Hadimeri H, Wahlberg R, et al. Melanotan II: a possible cause of renal infarction: review of the literature and case report. CEN Case Rep. 2020;9(2):159-161. PubMed
Habbema L, Halk AB, Neumann M, et al. Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review. Int J Dermatol. 2017;56(10):975-980. PubMed
Deville M, Charlier C. Barbie drug identification: Not a child's play. J Forensic Sci. 2024;69(6):2331-2338. PubMed
U.S. Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks (Melanotan II, under nominated but withdrawn). Page last updated April 22, 2026. Accessed October 8, 2026. Source
Drugs@FDA. Afamelanotide subcutaneous implant, NDA 210797, original approval October 8, 2019. Source
Langendonk JG, Balwani M, Anderson KE, et al. Afamelanotide for Erythropoietic Protoporphyria. N Engl J Med. 2015;373(1):48-59. PubMed
Drugs@FDA. Bremelanotide acetate injection, NDA 210557, original approval June 21, 2019. Source
Bonchev A. Changes in Oral Mucosa Associated with Melanotan II Injections: A Case Report. Life (Basel). 2026;16(2):265. PubMed
Burian EA, Jemec GBE. Eruptive Melanocytic Nevi: A Review. Am J Clin Dermatol. 2019;20(5):669-682. PubMed
Sources are peer-reviewed publications indexed in PubMed and trial registrations on ClinicalTrials.gov. Each citation was checked against its PubMed record.
For research use only. Not for human consumption.
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