Melanotan I vs II: One Approved, One Not

Two compounds, one letter apart

Both are synthetic analogues of alpha-melanocyte-stimulating hormone, the hormone that tells skin cells to make the brown pigment melanin, and both were first reported in people in the mid-1990s by overlapping authors studying skin pigmentation ^{[5, 9]}. They then went in opposite directions. The first, published as melanotan-I, was developed into an approved drug under the name afamelanotide ^{[2, 5]}. The second, Melanotan II, was studied briefly in the 1990s, drifted toward sexual function, and was never itself developed into an approved product ^{[9, 13]}.

The chemistry explains part of the split. Afamelanotide is a 13-amino-acid peptide that acts at the melanocortin 1 receptor, the one that governs pigmentation ^[1]. Melanotan II is a cyclic analogue that acts at several melanocortin receptors at once, which is why the pilot study that showed it could darken skin also recorded spontaneous erections in the men who took it ^[9]. The table sets out the rest.

What Scenesse is approved to do

The approval is narrow. FDA approved the Scenesse implant under application 210797 on October 8, 2019 ^[6], and its label, in the version effective May 11, 2026, names one use: to increase pain-free light exposure in adults with a history of phototoxic reactions from erythropoietic protoporphyria, an inherited disease in which light exposure causes painful phototoxic reactions ^[1]. The product is a subcutaneous implant, dispensed on prescription ^[6].

Its evidence is measured in hours of daylight. In the two pivotal placebo-controlled trials, 74 patients in Europe and 94 in the United States, the primary endpoint was time spent in direct sunlight without pain; after six months the United States trial reported a median of 69.4 hours against 40.8 hours on placebo ^[3]. Most of the compound's other trial records are other skin conditions, such as vitiligo, and none of them supports a wider label ^{[2, 4]}.

Skin darkening appears on the label as a warning, not a benefit. The label states that afamelanotide may darken the skin generally and darken existing moles and freckles, and it recommends a full body skin examination twice a year ^[8]. Its most common side effects in the trials were implant site reactions, in 21 percent against 10 percent on the vehicle implant, and nausea, in 19 percent against 14 percent ^[8].

What the Melanotan II record contains

Four records carry a clinical-trial publication type, all published between 1996 and 2000 ^[10]. The first, a pilot phase I study, found that the peptide produced measurable darkening of the skin and, incidentally, erections ^[9]. The next three followed the incidental finding into erectile dysfunction rather than tanning. Across the five names the compound goes by, the one trial-type record that touches tanning is that 1996 pilot in three volunteers ^[11].

What accumulated after the trials stopped is a case-report literature. PubMed indexes 23 case reports on the compound, and 9 of the records that mention melanoma are case reports ^[11]. Published cases describe melanoma in association with use, a kidney infarction, priapism and systemic toxicity with muscle breakdown after injection ^{[15, 16, 20, 17]}. Case reports show association, not cause; no controlled study of cosmetic tanning stands beside them ^[11].

FDA's statement on the compound, still published among substances whose nominations were withdrawn, is that compounded drugs containing it may pose a risk of immune reactions, and that published case reports discuss serious adverse events including melanoma, a brain swelling syndrome called posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism ^[12]. The Melanotan II evidence review reads each record.

What is the legal position of each?

No approved product is indicated for tanning as of September 2026. Scenesse is a prescription implant labeled for the one disease named above ^{[1, 6]}, and the approval belongs to that product and its label rather than to the compound under any other name. Melanotan II has no approved product, appears in no category of the section 503A bulks list published on May 14, 2026, and left Category 2 only because its nominators withdrew the nomination, with FDA's safety finding left standing ^{[14, 12]}.

Both names also turn up in enforcement. In April 2020 FDA warned a Kentucky compounding pharmacy that products it made with Melanotan II and twenty-one other substances were not eligible for the compounding exemptions ^[18]; in October 2020 that pharmacy, Tailor Made Compounding, pleaded guilty to distributing unapproved new drugs, and the Justice Department's account of the plea agreement names Melanotan II among them ^[19].

Material sold online as "melanotan 1" or "melanotan 2" is sold as research-use-only chemical supply. It is not the Scenesse implant, it is not made under its application, and nothing in the 2019 approval extends to it. The melanocortins class page files both compounds beside PT-141 and setmelanotide, the two other approved drugs that act on the same receptor family.

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