What is the difference between Melanotan 1 and Melanotan 2?

Receptor selectivity. Melanotan 1 is selective for MC1R, the receptor governing pigmentation, and was developed into the approved drug afamelanotide. Melanotan 2 binds non-selectively across the melanocortin receptor family, producing a broader and less predictable range of effects, and holds no regulatory approval anywhere.

How is PT-141 related to Melanotan 2?

PT-141 is derived from it. Melanotan 2 is the parent structure, and PT-141 was developed by narrowing that activity toward the MC4R receptor. That narrower profile is what made its approval as bremelanotide in 2019 possible.

Why does Melanotan 2 have no approved use when the other two do?

Because it was never refined toward a single receptor. Regulatory approval generally requires a well-characterised mechanism for a defined indication, and a compound acting across the whole receptor family is difficult to characterise that precisely. Both approved compounds are the result of narrowing activity down.

Are these compounds the same as tanning products?

No. These are research-grade materials for laboratory study, not cosmetic or therapeutic products. They are not approved by the TGA for human or veterinary use, and nothing here constitutes medical advice or a therapeutic claim.

Which is the best characterised of the three?

Melanotan 1, as afamelanotide — it holds FDA, EMA and TGA approval, which is rare in this field. PT-141 follows with FDA approval and Phase 3 data. Melanotan 2 has the smallest and most preclinical literature of the three.

Research Library›Comparisons›Melanotan 1 vs Melanotan 2 vs PT-141

Melanocortin Comparison

Melanotan 1 vs Melanotan 2 vs PT-141: Selectivity Is the Whole Story

Three compounds from one family, routinely treated as interchangeable. They are not. Which melanocortin receptors each one binds determines what it does — and explains why two hold regulatory approval and one does not.

8 min read·5 studies cited·Updated July 2026

Quick Reference

Melanotan 1	MC1R-selective — approved as afamelanotide
Melanotan 2	Non-selective — research compound only
PT-141	MC4R-focused — approved as Vyleesi (2019)
The variable	Receptor selectivity, not potency
Status	Research use only — not TGA approved

The Short Answer

The melanocortin system has five receptors (MC1R through MC5R) doing quite different jobs — MC1R governs pigmentation, MC4R sits in the brain and influences appetite and sexual arousal pathways. What separates these three compounds is which of those receptors they bind.

Melanotan 1 is selective for MC1R. PT-141 acts chiefly at MC4R. Melanotan 2 is non-selective and binds across the family — which is precisely why it produces a wider and less predictable range of effects than either.

	Melanotan 1	Melanotan 2	PT-141
Also known as	Afamelanotide (Scenesse)	MT-II	Bremelanotide (Vyleesi)
Receptor profile	MC1R-selective	Non-selective across MC1R–MC5R	Primarily MC4R
Studied for	Melanogenesis, photoprotection	Broad melanocortin reference compound	Central arousal pathways
Regulatory status	FDA, EMA and TGA approved (as afamelanotide)	No approval anywhere	FDA approved 2019 (as bremelanotide)
Relationship	Parent-family compound	Parent structure PT-141 derives from	Derived from Melanotan 2
Selectivity	High	Low — the defining trait	Moderate to high

Why Selectivity Decides Everything

Selectivity, in plain language: picture the melanocortin receptors as five rooms along a corridor, each doing a different job. One room handles skin pigment. Another sits in the brain and deals with appetite and arousal. A selective compound is a key cut for exactly one of those doors. A non-selective compound is a master key that opens all five. The master key sounds more powerful, and in a sense it is — but once every door is open you can no longer say which room produced which result, and that is a serious problem when the whole point is to understand a mechanism. Melanotan 1 is a key for the pigment room. PT-141 is a key for the brain room. Melanotan 2 is the master key, and that is precisely why it remained a research compound while the other two were developed into approved medicines for specific, well-defined jobs.

A selective compound engages one receptor and leaves the rest largely alone. A non-selective one engages several, producing effects across multiple systems simultaneously — which is useful in research when you want to probe the whole family, and unhelpful when you want to isolate a single mechanism.

This is the direct explanation for the regulatory picture. Melanotan 1 targets MC1R and pigmentation specifically, and was developed into afamelanotide, approved for a rare photosensitivity disorder. PT-141 was derived from Melanotan 2 precisely to narrow its activity toward MC4R, and that narrowing is what made approval as bremelanotide possible.

Melanotan 2 was never narrowed. It remains the broad parent structure — scientifically valuable as a reference compound for studying the melanocortin system as a whole, but with no approved use anywhere.

The lineage in one line: melanotan 2 is the parent structure; PT-141 is the refinement of it toward MC4R. They are not competitors — one is descended from the other, and the descendant exists because narrower activity proved more useful than broader activity.

Melanotan 1 sits alongside both as the MC1R-selective member of the same family, developed down an entirely separate path toward pigmentation research.

Where the Evidence Stands

The three differ sharply in how well characterised they are, and the gap runs in the same direction as selectivity.

Melanotan 1 / afamelanotide holds full approval from the FDA, EMA and TGA for erythropoietic protoporphyria — an unusual position for a compound in this field, and the strongest evidence base of the three.

PT-141 / bremelanotide gained FDA approval in 2019 following Phase 3 trials, making it the first compound to approach sexual function research through central neural pathways rather than vascular ones.

Melanotan 2 has no approval in any jurisdiction. Its published literature is largely preclinical and mechanistic, and it is supplied strictly as a research compound. Because its activity spans the receptor family, its effects are correspondingly harder to attribute to any single mechanism.

Frequently Asked Questions

Compiled by the Southern Pacific Labs research team. Last updated July 2026.

Browse the research range →

Published References

Langendonk JG, Balwani M, Anderson KE, et al. “Afamelanotide for Erythropoietic Protoporphyria.” The New England journal of medicine, 2015. PubMed
Kingsberg SA, Clayton AH, Portman D, et al. “Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials.” Obstetrics and gynecology, 2019. PubMed
Molinoff PB, Shadiack AM, Earle D, et al. “PT-141: a melanocortin agonist for the treatment of sexual dysfunction.” Annals of the New York Academy of Sciences, 2003. PubMed
Wessells H, Gralnek D, Dorr R, et al. “Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction.” Urology, 2000. PubMed
Dorr RT, Lines R, Levine N, et al. “Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.” Life sciences, 1996. PubMed