Melanotan I vs Melanotan II: Research Comparison

Melanotan I and Melanotan II are two synthetic analogues of alpha-melanocyte stimulating hormone (α-MSH), a naturally occurring neuropeptide derived from proopiomelanocortin (POMC). Both were developed through research programmes initially aimed at investigating photoprotection and melanogenesis. Despite sharing a common origin and overlapping receptor activity, they differ meaningfully in their selectivity, molecular structure, and research profiles.

This article provides a comparative research overview of Melanotan I and Melanotan II. All Bloom Vitality products are supplied strictly for in vitro laboratory and research use only.

Common Background: α-MSH and the Melanocortin System

α-MSH is a 13-amino acid peptide that acts at melanocortin receptors (MC1R–MC5R). It plays a role in pigmentation, energy homeostasis, inflammation, and sexual function. Both Melanotan I and Melanotan II are synthetic analogues designed to mimic and extend the activity of α-MSH, with modifications conferring improved stability and receptor affinity compared to the native peptide.

Melanotan I (Afamelanotide)

Melanotan I, also known by the INN afamelanotide, is a linear 13-amino acid analogue of α-MSH with a single amino acid substitution (norleucine at position 4 and D-phenylalanine at position 7) that confers increased receptor binding affinity and resistance to enzymatic degradation.

• Receptor selectivity — Melanotan I demonstrates relatively selective agonism at MC1R, the primary receptor mediating melanogenesis in melanocytes.
• Primary research area — Photoprotection and pigmentation. Afamelanotide has received regulatory approval in the European Union (as Scenesse®) for the prevention of phototoxicity in adults with erythropoietic protoporphyria (EPP) — making it one of the few melanocortin analogues with an approved therapeutic indication.
• Research profile — More selective, with a narrower range of investigated effects compared to Melanotan II.

Melanotan II

Melanotan II is a cyclic 7-amino acid analogue of α-MSH. Its cyclic structure confers greater metabolic stability and enhanced receptor binding, but also broader melanocortin receptor activity.

• Receptor selectivity — Melanotan II acts at MC1R, MC3R, MC4R, and MC5R. The additional MC4R agonism in particular accounts for its wider range of investigated biological effects compared to Melanotan I.
• Primary research areas — Pigmentation (MC1R), sexual function (MC4R), appetite and energy homeostasis (MC3R/MC4R), and inflammation.
• Research profile — Broader, with a more extensive preclinical literature across multiple physiological systems.

Key Differences at a Glance

Feature	Melanotan I	Melanotan II
Structure	Linear 13-AA	Cyclic 7-AA
Primary receptor	MC1R	MC1R, MC3R, MC4R, MC5R
Pigmentation research	Yes (primary focus)	Yes
Appetite/energy research	Limited	Yes (MC3R/MC4R)
Sexual function research	No	Yes (MC4R)
Regulatory status	EU approved (EPP indication)	Not approved

Research Material

Bloom Vitality supplies Melanotan II 10mg as a lyophilised research vial, independently third-party tested for purity and potency. Melanotan I (afamelanotide) is not currently stocked. Batch-specific Certificates of Analysis are available via our Certificates & Documentation page and Testing & Quality page. All products are part of the research peptides UK catalogue.

For research and laboratory use only. This article is provided for informational purposes and does not constitute medical advice.