Melanotan 1 vs Melanotan 2: What Is the Difference? (Research Overview)

Melanotan 1 and Melanotan 2 are both synthetic analogs of the natural hormone α-melanocyte–stimulating hormone (α-MSH) studied in melanocortin and pigmentation research, but they differ most importantly in receptor selectivity. Melanotan I (afamelanotide) is a more selective, α-MSH–oriented analog whose activity is directed largely at the melanocortin-1 receptor (MC1R). Melanotan II is a broader, non-selective melanocortin-receptor agonist active across multiple melanocortin receptor subtypes (MC1R, MC3R, MC4R and MC5R). This article is an educational research overview only.

Both compounds are sold by Bolt Peptide strictly as research-use-only (RUO) materials. The information below summarizes preclinical and laboratory research and is not a description of effects in humans.

Quick comparison

• Structure — Melanotan I: a linear (open-chain) modified analog of α-MSH. Melanotan II: a smaller cyclic heptapeptide closed by a lactam bridge.
• Receptor selectivity — Melanotan I: oriented toward MC1R, the receptor most associated with melanin pigmentation pathways. Melanotan II: non-selective, binding multiple melanocortin receptors.
• Research focus — Melanotan I: studied around MC1R-driven pigmentation biology; the related compound afamelanotide has an approved photoprotective medical use. Melanotan II: used as a broad pharmacological tool across melanocortin-receptor research.

What is Melanotan I?

Melanotan I, also known as afamelanotide, is a synthetic analog of α-MSH. In research literature it is described as a modified amino-acid analog of α-MSH that binds the MC1R and influences melanin synthesis pathways in preclinical models. Its relatively more selective profile makes it a frequent reference compound in MC1R-focused pigmentation studies. For a deeper breakdown, see our full Melanotan I article.

What is Melanotan II?

Melanotan II is a cyclic heptapeptide analog of α-MSH, first characterized in melanocortin research as a superpotent melanotropic peptide. Because it activates melanocortin receptors broadly rather than selectively, it has been studied as a general-purpose research probe of melanocortin signaling. For more detail, see our full Melanotan II article.

Key differences studied in research

• Molecular form: Melanotan I is a linear analog of α-MSH, whereas Melanotan II is a smaller cyclic (lactam-bridged) heptapeptide.
• Receptor selectivity: Melanotan I is comparatively MC1R-oriented; Melanotan II is non-selective and engages MC1R, MC3R, MC4R and MC5R in laboratory studies.
• Potency profile: Melanotan II has been described in the literature as a superpotent melanotropic peptide relative to native α-MSH.

Research status and safety

Both Melanotan 1 and Melanotan 2 are offered here as research-use-only chemicals intended for in-vitro and laboratory investigation by qualified researchers. They are not dietary supplements, drugs, or cosmetics, and nothing here describes use in humans. As a separate matter of public record: afamelanotide — the compound corresponding to the Melanotan I class — was approved by the U.S. FDA in 2019 (brand name Scenesse) to increase pain-free light exposure in adults with a history of phototoxic reactions from erythropoietic protoporphyria (EPP). That approval is a regulated medical product administered by clinicians and is entirely distinct from RUO research material.

Handling

Researchers working with lyophilized peptides should follow standard laboratory practice for preparation and storage. See our reconstitution guide, and browse available materials in the peptide catalog.

FAQ

Is Melanotan 1 or Melanotan 2 “stronger”? The two are not directly interchangeable on a potency scale because they differ in receptor selectivity. Melanotan II is described in the literature as superpotent at melanocortin receptors broadly, whereas Melanotan I research centers on its more MC1R-selective profile.

What is the main structural difference? Melanotan I is a linear analog of α-MSH, while Melanotan II is a smaller cyclic heptapeptide closed by a lactam bridge.

Are these approved for human use? No. Both are sold strictly as research-use-only compounds. Separately, the afamelanotide (Melanotan I class) medical product Scenesse is FDA-approved only for a specific condition (EPP) and is a clinician-administered drug, not an RUO research chemical.

References

1. Afamelanotide. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. NCBI Bookshelf.
2. Dorr RT, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide. Life Sci. 1996.
3. Sprague JE, et al. Melanocortin-receptor agonist melanotan-II (MTII) in MC3R-deletion mice. Neuropeptides. 2013.

For research use only. Not for human or veterinary use, diagnosis, or therapy. Statements have not been evaluated by the FDA.