Melanotan I
| Category | Compounds |
|---|---|
| Also known as | Melanotan-1, Afamelanotide Precursor, NDP-α-MSH, [Nle4, D-Phe7]-α-MSH |
| Last updated | 2026-04-14 |
| Reading time | 3 min read |
| Tags | melanocortintanningphotoprotectionalpha-msh-analogresearch |
Overview
Melanotan I (MT-I) is a synthetic analog of α-melanocyte-stimulating hormone (α-MSH), designed in the 1980s at the University of Arizona as part of research into safer alternatives to UV tanning. Structural modifications at positions 4 and 7 of α-MSH produced a peptide ([Nle4, D-Phe7]-α-MSH) with greatly improved enzymatic stability and potency at melanocortin receptors. Developed under various names, the molecule became Afamelanotide, which is approved for erythropoietic protoporphyria.
The research trajectory of Melanotan I is distinct from Melanotan II, which was developed in parallel for different indications. MT-I is more selective for the melanocortin receptors involved in pigmentation (MC1R) and has become an approved drug, whereas MT-II has broader receptor activity including MC4R, which is why MT-II-derived PT-141 (bremelanotide) was developed for sexual function.
In research contexts, Melanotan I is discussed alongside Afamelanotide, α-MSH, and melanocortin-acting drugs such as Setmelanotide (MC4R-selective for rare obesity).
Structure / Chemistry
Melanotan I is the linear tridecapeptide [Nle4, D-Phe7]-α-MSH. The substitution of methionine-4 with norleucine blocks oxidation at that position, and the substitution of L-phenylalanine-7 with D-phenylalanine blocks proteolytic cleavage at a key bond. Together, these modifications dramatically extend biological activity relative to native α-MSH.
Mechanism of Action
MT-I agonizes melanocortin receptors, with meaningful activity at MC1R on melanocytes where it stimulates melanin synthesis and pigmentation. It also acts at other MC receptors, although with different potency profiles than MT-II. In approved clinical use as afamelanotide, sustained-release implants deliver the peptide to increase eumelanin and provide photoprotection in patients with erythropoietic protoporphyria.
Research Summary
| Area | Finding | Reference |
|---|---|---|
| Chemistry | Development as stable α-MSH analog | Sawyer et al., PNAS 1980 |
| EPP approval | Photoprotection in erythropoietic protoporphyria | Langendonk et al., NEJM 2015 |
| Pigmentation | Skin darkening in human studies | Dorr et al., Life Sci 1996 |
| Pharmacology | MC1R potency and selectivity | Hadley et al., Peptides 1984 |
| Mechanism | Eumelanin production in melanocytes | Multiple melanocortin research studies |
Pharmacokinetics
Melanotan I has a substantially longer biological half-life than native α-MSH due to its stabilizing modifications. Clinical use employs a bioresorbable subcutaneous implant (afamelanotide) for controlled release over approximately two months. Research injections historically used daily or every-other-day subcutaneous administration. Dosing details are trial parameters, not guidance.
Common Discussion Topics
- Distinction between research Melanotan I and approved afamelanotide implants.
- Photoprotective vs. cosmetic tanning contexts.
- MC1R-preferential activity vs. MT-II's broader profile.
- Regulatory status — illicit cosmetic use of research MT-I vs. licensed afamelanotide.
- Safety concerns including dark mole changes and need for dermatologic surveillance.
Related Compounds
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Related entries
- Afamelanotide— A synthetic 13-amino-acid analog of alpha-melanocyte-stimulating hormone, afamelanotide is an FDA-approved melanocortin 1 receptor agonist administered as a subcutaneous implant to increase pain-free light exposure in patients with erythropoietic protoporphyria.
- Melanocyte-Stimulating Hormone (Alpha-MSH)— A 13-amino-acid neuropeptide derived from POMC that regulates melanogenesis, appetite, energy homeostasis, and inflammation through the melanocortin receptor system, and serves as the parent molecule of the anti-inflammatory tripeptide KPV.
- Melanotan II— A synthetic cyclic analog of alpha-melanocyte-stimulating hormone that activates multiple melanocortin receptors, studied for UV-free tanning with notable secondary effects on sexual arousal, appetite suppression, and fat metabolism.
- PT-141— A melanocortin receptor agonist (MC3R/MC4R) FDA-approved as Vyleesi for hypoactive sexual desire disorder in premenopausal women, derived from Melanotan II research.
- Setmelanotide— A synthetic cyclic octapeptide melanocortin 4 receptor agonist, setmelanotide is an FDA-approved treatment for chronic weight management in patients with obesity due to specific monogenic defects in the leptin-melanocortin signaling pathway, including POMC, PCSK1, and LEPR deficiency.