Melanotan I vs Setmelanotide

Both are approved synthetic melanocortin agonists but for different receptors: afamelanotide (melanotan-1) at MC1R for photoprotection in erythropoietic protoporphyria, setmelanotide at MC4R for rare genetic obesity.

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Melanotan I

A linear α-MSH analogue that selectively activates MC1R, approved (as an implant) to prevent phototoxicity in erythropoietic protoporphyria.

BEST STUDIED FOR

Melanocortin

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Setmelanotide

A melanocortin-4 receptor agonist approved for rare genetic obesities caused by defects in the leptin–melanocortin pathway.

BEST STUDIED FOR

Melanocortin

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SIDE BY SIDE

	Melanotan I	Setmelanotide
The key difference	MC1R — pigmentation	MC4R — appetite
Class	Melanocortin	Melanocortin
Mechanism	Afamelanotide binds the melanocortin-1 receptor on melanocytes, increasing eumelanin production.	MC4R neurons integrate leptin and POMC signals to regulate hunger and energy expenditure.
Status	Approved in the EU (2014) and US (2019) as a subcutaneous implant for erythropoietic protoporphyria (EPP). Unregulated injectable "melanotan" products are a separate, unapproved market.	Approved (2020 onward) for POMC, PCSK1 or LEPR deficiency obesity and Bardet–Biedl syndrome; studied in hypothalamic obesity.
Reported safety signals	In the EPP trials the implant was well tolerated; dermatology reviews warn about unregulated use of melanotan products and the need for mole surveillance.	Trials report injection-site reactions and skin hyperpigmentation (an expected MC1R effect), with nausea early in treatment.
A key study	Randomised trials measured pain-free sunlight exposure and safety with afamelanotide implants in EPP. (N Engl J Med 2015, PMID 26132941)	Summarises setmelanotide’s development and first approval for POMC, PCSK1 or LEPR deficiency obesity. (Drugs 2021, PMID 33638809)

WHEN TO RESEARCH WHICH

The pair shows how melanocortin receptor subtype decides the effect. Both are discussed here strictly as research compounds; nothing on this page is medical advice or a dosing guide.

REFERENCES (PUBMED)

[Melanotan I] Afamelanotide for Erythropoietic Protoporphyria — N Engl J Med 2015. PMID 26132941
[Melanotan I] Afamelanotide: A Review in Erythropoietic Protoporphyria — Am J Clin Dermatol 2016. PMID 26979527
[Melanotan I] Afamelanotide in protoporphyria and other skin diseases: a review — Postepy Dermatol Alergol 2024. PMID 38784937
[Setmelanotide] Setmelanotide: First Approval — Drugs 2021. PMID 33638809
[Setmelanotide] Efficacy and safety of setmelanotide, an MC4R agonist, in individuals with severe obesity due to LEPR or POMC deficiency: single-arm, open-label, multicentre, phase 3 trials — Lancet Diabetes Endocrinol 2020. PMID 33137293
[Setmelanotide] Efficacy and safety of setmelanotide, a melanocortin-4 receptor agonist, in patients with Bardet-Biedl syndrome and Alström syndrome: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial with an open-label period — Lancet Diabetes Endocrinol 2022. PMID 36356613

FREQUENTLY ASKED

What is the difference between Melanotan I and Setmelanotide?

What is the regulatory status of Melanotan I and Setmelanotide?

Melanotan I: Approved in the EU (2014) and US (2019) as a subcutaneous implant for erythropoietic protoporphyria (EPP). Unregulated injectable "melanotan" products are a separate, unapproved market. Setmelanotide: Approved (2020 onward) for POMC, PCSK1 or LEPR deficiency obesity and Bardet–Biedl syndrome; studied in hypothalamic obesity.

What safety signals have been reported?

Melanotan I: In the EPP trials the implant was well tolerated; dermatology reviews warn about unregulated use of melanotan products and the need for mole surveillance. Setmelanotide: Trials report injection-site reactions and skin hyperpigmentation (an expected MC1R effect), with nausea early in treatment.

Which studies is this comparison based on?

For Melanotan I: “Afamelanotide for Erythropoietic Protoporphyria” (PMID 26132941); “Afamelanotide: A Review in Erythropoietic Protoporphyria” (PMID 26979527); “Afamelanotide in protoporphyria and other skin diseases: a review” (PMID 38784937). For Setmelanotide: “Setmelanotide: First Approval” (PMID 33638809); “Efficacy and safety of setmelanotide, an MC4R agonist, in individuals with severe obesity due to LEPR or POMC deficiency: single-arm, open-label, multicentre, phase 3 trials” (PMID 33137293); “Efficacy and safety of setmelanotide, a melanocortin-4 receptor agonist, in patients with Bardet-Biedl syndrome and Alström syndrome: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial with an open-label period” (PMID 36356613).