Reference
Melanotan I vs Melanotan II
Two analogues of the same pigment hormone, made in the same university lab. Their shapes differ, and so did their fates: one is an approved medicine, the other never was.
The names suggest a first and second version of one product. In fact Melanotan I and II are different molecules with different shapes, and their histories split completely. This page compares the molecules and what became of them; it makes no claim about what either does.
| Melanotan I | Melanotan II | |
|---|---|---|
| Other name | Afamelanotide | None (no international name) |
| Length | 13 amino acids | 7 amino acids |
| Shape | Linear chain | Ring (cyclic) |
| Modelled on | Alpha-MSH, two amino acids changed | A shortened, cyclised core of alpha-MSH |
| Made at | University of Arizona, 1980s | University of Arizona, 1980s |
| Became | Scenesse, approved EU 2014 and US 2019 | Dropped in 2000; led to bremelanotide (PT-141) |
The same starting point
Both are built on alpha-MSH, the hormone that signals skin cells to make melanin. In the 1980s a University of Arizona group led by Mac Hadley and Victor Hruby set out to make versions that would last longer than the natural hormone, with the idea of a tan without the sun as protection against skin cancer.
A chain and a ring
Melanotan I keeps the full 13-amino-acid length of alpha-MSH and changes two of them, which makes it far more durable. It stays a straight chain.
Melanotan II is cut down to seven amino acids and closed into a ring. The ring is what defines it; it also makes the molecule bind more broadly across the melanocortin receptor family than Melanotan I does.
Two different endings
Melanotan I was developed by the Melbourne company Clinuvel into Scenesse, a small implant placed under the skin every two months, approved in Europe in 2014 and by the FDA in October 2019 for a rare condition in which sunlight causes severe pain. It is not approved for cosmetic tanning anywhere.
Melanotan II was dropped in 2000. An unplanned finding in its early testing was spun off into a close relative, PT-141 (bremelanotide), approved by the FDA in 2019 under the name Vyleesi. Melanotan II itself has never been approved, and regulators including New Zealand’s have warned about material sold under its name.
Buy in New Zealand
Prices, sizes and stock: Melanotan I in New Zealand · Melanotan II in New Zealand.
