Melanotan II — wholesale 10-vial kits

Research context

Melanotan II, almost always abbreviated MT-II, is a cyclic lactam analog of alpha-melanocyte-stimulating hormone built around the α-MSH pharmacophore His-D-Phe-Arg-Trp. Its structure, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, carries an acetylated N-terminal norleucine, a side-chain lactam bridge between the aspartate and the lysine, and a C-terminal amide. It came out of the melanocortin chemistry program of Hruby, Hadley, Al-Obeidi and colleagues at the University of Arizona, where a series of conformationally constrained cyclic α-MSH analogs was designed from molecular-dynamics modeling of the parent hormone and reported in the Journal of Medicinal Chemistry in 1989.

Three design elements govern how MT-II behaves as a reference ligand. The Asp–Lys lactam closes a 23-membered ring that locks the pharmacophore into the bioactive turn, which raised melanotropic potency roughly 100-fold over α-MSH in the classical frog (Rana pipiens) and lizard (Anolis carolinensis) skin melanocyte bioassays used in the original structure–activity work. The D-phenylalanine at position 7 fixes the ring geometry and blocks proteolysis at the most labile backbone position. The N-terminal acetyl and the non-proteinogenic norleucine remove the free amine and the oxidation-prone methionine of the natural sequence. The single histidine and arginine side chains set the molecule's ionization behavior, which a 1994 physicochemical study characterized through its pKa values and octanol partition coefficient — numbers that matter when choosing an assay buffer.

The defining pharmacological feature of MT-II is that it is non-selective: it is a potent agonist across the cloned human melanocortin receptors MC1R, MC3R, MC4R and MC5R, and later structure–activity series built on the same scaffold — substituting bulky aromatic residues at position 7, or proline at position 6 — were what produced subtype-selective agonists and antagonists such as SHU-9119 and PG-931. A 2022 Journal of Medicinal Chemistry study that replaced the lactam with xylene-derived thioethers described MT-II explicitly as a potent and unselective agonist of the human melanocortin receptors, using it as the parent against which functionally selective analogs were measured.

That non-selectivity is exactly what makes MT-II useful at the bench: it is a broad-spectrum reference agonist for melanocortin panels rather than a tool for isolating one subtype. Typical laboratory use spans cAMP-accumulation and β-arrestin-recruitment assays across recombinant MC1R–MC5R lines, competition binding against radiolabeled NDP-α-MSH, structure–activity series on cyclic α-MSH analogs, and central melanocortin-signaling studies in rodent models — a 1997 Nature study used intracerebroventricular MT-II with the antagonist SHU-9119 to probe melanocortin circuitry. It is also an analytical reference where distinguishing MT-II from its deamidated relative PT-141 (bremelanotide) matters: the two differ only at the C-terminus, MT-II ending in an amide and bremelanotide in a free acid, and MT-II was the chemical precursor from which that later molecule was developed.

Regulatory position, stated factually: Melanotan II is not an FDA-approved drug and is not the active ingredient of any approved product. FDA has issued warnings regarding unapproved melanotan products — FDA Import Alert 66-41 lists Melanotan (I and II) among unapproved new drugs promoted online under a research-use label, and FDA lists Melanotan II among bulk drug substances nominated for compounding and then withdrawn by the nominators, noting published reports of serious adverse events. None of that is an approval. WholesalePeptide.us supplies MT-II as a research reference standard for in-vitro, analytical and preclinical laboratory research only.

The intramolecular lactam lowers the molecule's mass relative to the equivalent linear sequence by the water lost in forming the bridge, which is the quickest LC-MS check that the ring is closed. Identity on each lot COA is confirmed by LC-MS against the cyclic structure, and the counter-ion is reported separately, since the material is commonly supplied as the acetate.

Research areas

• melanocortin MC1R–MC5R receptor pharmacology
• cyclic α-MSH analog structure–activity relationships
• cAMP and β-arrestin assays across melanocortin subtypes
• central melanocortin signaling in rodent models
• reference agonist for melanocortin binding panels
• differentiation of MT-II from bremelanotide by LC-MS

U.S. regulatory status of the compound (as an active ingredient): Not approved by the FDA. The material sold here is a research reference chemical, not a drug product.

Handling and storage

• Store lyophilized vials at −20 °C, sealed, protected from light and moisture.
• Let the vial equilibrate to room temperature before opening to limit condensation.
• Reconstitute in an appropriate sterile buffer or solvent according to your laboratory SOP.
• Aliquot reconstituted material and avoid repeated freeze–thaw.