What Is Melanotan? Melanotan I vs Melanotan II
Melanotan is the name for two lab-made versions of a natural pigment hormone. This guide explains Melanotan I vs Melanotan II, the melanocortin receptors they act on, and how they led to afamelanotide and PT-141.
Melanotan at a glance
Melanotan refers to two synthetic peptides modelled on alpha-melanocyte stimulating hormone (alpha-MSH), the hormone that signals pigment cells to make melanin. Both came out of research at the University of Arizona in the 1980s, where scientists were looking for a way to stimulate pigmentation without UV exposure.
- Parent hormone
- Alpha-MSH
- Melanotan I
- Afamelanotide, 13 amino acids
- Melanotan II
- Cyclic, 7 amino acids
- Related peptide
- PT-141 (bremelanotide)
Melanotan I vs Melanotan II
| Compared | Melanotan I | Melanotan II |
|---|---|---|
| Structure | Linear, 13 amino acids | Cyclic (ring-shaped), 7 amino acids |
| Receptors | Mostly MC1R | MC1R, MC3R, MC4R and MC5R |
| Other names | Afamelanotide, MT1, MT-I | MT2, MT-II |
| Regulatory status | Approved as an implant for a rare light-sensitivity disorder | Never approved as a medicine |
- Alpha-MSH (natural)13
- Melanotan I13
- Melanotan II7
- PT-1417
Melanotan II and PT-141 are cut down to a 7-residue ring, which makes them more stable but less selective.
The key difference is selectivity. Melanotan I keeps the full-length shape of alpha-MSH with two substitutions that make it last longer, and it sticks closely to the MC1 receptor on pigment cells. Melanotan II is smaller and ring-shaped, which makes it more stable but lets it bind several melanocortin receptors around the body.
The melanocortin receptors
There are five melanocortin receptors, and which ones a peptide reaches decides what it does in research models:
| Receptor | Where it is found | Research focus |
|---|---|---|
| MC1R | Pigment cells (melanocytes) | Melanin and pigmentation |
| MC2R | Adrenal gland | Cortisol release (the ACTH receptor) |
| MC3R | Brain and other tissues | Energy balance |
| MC4R | Brain | Appetite and sexual function signalling |
| MC5R | Exocrine glands | Gland secretions |
From Melanotan I to afamelanotide
Melanotan I went on to become afamelanotide, developed by the Australian company Clinuvel and sold as an implant called Scenesse. It was approved in Europe in 2014 and in the United States in 2019 for erythropoietic protoporphyria, a rare genetic condition that causes severe pain on light exposure.
From Melanotan II to PT-141
Because Melanotan II acts on the MC4 receptor in the brain, researchers studied its non-pigment effects too. That work produced bremelanotide, better known as PT-141 (see what is PT-141), a close relative of Melanotan II that is studied mainly for its action at the MC4 receptor. Bremelanotide was approved in the United States in 2019 as a separate medicine.
- 1980sMelanotan research begins at the University of Arizona.
- 1990sMelanotan II and its MC4R effects are studied, leading to the PT-141 programme.
- 2014Afamelanotide (Melanotan I) approved in Europe as Scenesse.
- 2019FDA approves Scenesse and, separately, bremelanotide (PT-141).
Melanotan in Australia
Australian health authorities have warned consumers about unregistered melanotan products sold for tanning, including nasal sprays. Research-grade Melanotan I, Melanotan II and PT-141 are supplied for laboratory research only, are not for human use, and are not tanning products.
Further reading
- How to reconstitute peptides
- How to read a peptide COA
- What is PT-141?
- What is KPV? (another alpha-MSH fragment)
For laboratory research use only. Not for human consumption. Not medical or legal advice.
