# What Is Melanotan 2? The Melanocortin Peptide Explained > What is Melanotan 2? A synthetic melanocortin peptide (MT2, Melanotan II) — what it is, where it came from, and how it differs from Melanotan I and PT-141. The molecule, the names, the origin, and how it sits against its approved cousins. ## The short version What is Melanotan 2? It is a small, lab-made peptide — a short chain of amino acids — built to copy a natural body hormone called alpha-MSH that tells skin to make pigment. The lab version is stronger and longer-lasting. Injected, it darkens skin without sun, cuts appetite, and (in men) can trigger erections. It goes by several names. **Melanotan**, **Melanotan II**, **MT-2**, and **MT2** all point to the same compound. It is not a tanning product and not a medicine — no regulator has approved it for any use [4]. It was designed by university scientists in the 1980s, never finished clinical development, and now circulates as an unregulated research chemical. Below: the chemistry in plain words, the origin story, and how it differs from the two related compounds that did get approved. ## Melanotan, MT2, and Melanotan II — the names The naming is a common source of confusion, so here it is plainly. **Melanotan** on its own usually means this compound, though it is sometimes used loosely for the whole family. **Melanotan II** is the precise name. **MT-2** and **MT2** are the everyday short forms. Chemically it is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — a cyclic (ring-shaped) seven-unit peptide, molecular weight about 1024 Da, CAS 121062-08-6. What **MT2** is not: it is not Melanotan I, and it is not the approved sexual-function drug derived from this scaffold. Those are separate compounds with separate profiles, covered below. And searching **Melanotan II** will surface both the legitimate research literature and a large illicit market — this site digests only the former [22]. ## Where it came from Melanotan 2 was designed in the late 1980s by Victor Hruby, Mac Hadley, and colleagues at the University of Arizona [29]. The idea was elegant: if you could darken skin with a drug instead of sun, you might cut UV exposure and skin-cancer risk. They built a superpotent cyclic analog of alpha-MSH, resistant to the enzymes that chew up the natural hormone. A pilot Phase I study showed it worked — skin darkened [1]. Researchers also noticed it triggered erections, which spun off a small erectile-dysfunction study and, eventually, a separate MC4R-focused agonist for sexual dysfunction [29]. The original tanning program never reached the market. From the mid-2000s, an illicit "melanotan" trade filled the gap, selling unlicensed tanning injections despite regulator warnings [30]. ## Melanotan 2 vs Melanotan I vs PT-141 Three compounds, one family, easy to confuse. - **Melanotan 2 (this compound):** non-selective melanocortin agonist — hits MC1R through MC5R. Broadest effect (pigment plus appetite, sexual, behavioral). No regulatory approval anywhere [4]. - **Afamelanotide (Melanotan I):** a linear analog, more selective toward MC1R, so its action leans pigment-only. It is the one melanocortin tanning-type analog with regulatory approval — for the rare inherited disorder erythropoietic protoporphyria (EPP), which causes painful sun reactions [27]. That approval does not extend to Melanotan 2. - **Bremelanotide (PT-141):** a cyclic agonist derived from the Melanotan 2 scaffold, optimized toward MC4R for sexual effects with reduced pigment activity. It is approved for hypoactive sexual desire disorder in premenopausal women [28]. That approval does not extend to Melanotan 2 either. The takeaway: two relatives crossed the regulatory finish line; Melanotan 2 did not. Its controlled human data is limited to small Phase I studies, and its long-term safety remains unknown [6]. For how the receptors produce these differences, see the [melanotan 2 mechanism of action](/mechanism-of-action) page. --- A brain-first reading of the melanocortin literature — studies summarized, nothing prescribed.