Melanotan 1: Structure, Mechanism and Research Status

Melanotan 1 is a synthetic, 13-amino-acid analogue of alpha-melanocyte-stimulating hormone (α-MSH), also known as afamelanotide or [Nle4, D-Phe7]-α-MSH. It acts mainly on the melanocortin-1 receptor (MC1R). First made in 1980 for laboratory research, it is now an approved prescription drug in some regions, while research-grade material is for laboratory use only.

Melanotan 1 key takeaways

• What it is: a linear peptide made by changing two amino acids in natural α-MSH (PMID 6777774).
• Main target: the melanocortin-1 receptor on pigment cells, with lower binding to MC3, MC4 and MC5 receptors (PMID 7774675).
• Why it was made: the two changes made the peptide resist breakdown by serum enzymes and gave it much longer activity in lab tests (PMID 6777774).
• Human data: controlled clinical trials exist, but only for one formulation (a slow-release implant) under medical supervision (PMID 26132941).
• Status: an afamelanotide implant is an approved prescription medicine in the EU (2014) and the US (2019). Research-grade melanotan 1 peptide is not a medicine and is not for human use.

Melanotan 1 key facts table

The table below collects the identity data researchers check first. Values come from the PubChem compound record (CID 16197727) and the original 1980 synthesis paper.

Source for the identity rows: PubChem compound summary for afamelanotide.

Background and discovery of melanotan 1

Melanotan 1 began as a chemistry question at the University of Arizona. Natural α-MSH is a short hormone made by the body. It darkens frog skin in the lab, but the effect fades fast because enzymes break the hormone down.

In 1980, Sawyer, Hruby, Hadley and colleagues noticed something odd. When they heated α-MSH in an alkaline solution, the treated hormone stayed active for much longer. Chemical analysis showed that heating had flipped some amino acids into their mirror-image form, mostly at positions 4 and 7 (PMID 6777774).

The team then built a peptide with those two changes on purpose: norleucine at position 4 and D-phenylalanine at position 7. The new analogue resisted serum enzymes. It was about 26 times as potent as α-MSH in a mouse melanoma adenylate cyclase test, and its effect lasted far longer (PMID 6777774). This compound later took the names Melanotan 1 and afamelanotide.

A 2006 review by Hadley and Dorr sums up the later path. Melanotan 1 (the linear peptide) went into clinical testing for skin pigmentation. Its cousin, Melanotan 2 (a shorter, cyclic peptide), went down a different research path (PMID 16412534).

Melanotan 1 structure

To read the structure, it helps to know two terms:

• Analogue: a molecule built to look like a natural one, with small, planned changes.
• D-amino acid: the mirror-image form of a normal (L) amino acid. Most enzymes in the body cannot easily cut next to a D-amino acid.

Melanotan 1 keeps all 13 positions of α-MSH. It also keeps the acetyl cap at the start and the amide cap at the end. Only two positions change:

The middle of the chain, His-Phe-Arg-Trp (positions 6 to 9), is the “core” that all melanocortin peptides share. A 1998 study of nine variants of the melanotan 1 peptide found that the tail end (Gly-Lys-Pro-Val) was important for binding to all four receptor types tested (PMID 9671118).

Melanotan 1 vs Melanotan 2: structure only

The two names sound alike, but the molecules are different:

• Melanotan 1: linear, 13 amino acids, the full α-MSH length.
• Melanotan 2: cyclic (ring-shaped) and truncated to a shorter chain (PMID 16412534).

Because the structures differ, findings for one compound should never be assumed for the other.

Melanotan 1 mechanism and receptor pathway

Melanotan 1 works by binding to melanocortin receptors. These are a family of five receptors (MC1R to MC5R) found on cell surfaces. They respond to hormones made from a larger protein called POMC (PMID 28220105).

Receptor binding data for melanotan 1

In a 1995 study, cells were engineered to carry one receptor type at a time. Radio-labelled melanotan 1 bound most tightly to MC1R. Binding to MC3R was weaker, and binding to MC5R was much weaker (PMID 7774675).

Data: COS cells expressing single receptor subtypes, PMID 7774675. A smaller Kd number means tighter binding.

Melanotan 1 pathway diagram

The steps below show the MC1R pathway as described in laboratory and review papers. It is a simplified research model, not a description of effects in people.

1. Binding: melanotan 1 attaches to MC1R on the surface of a melanocyte (pigment cell) (PMID 38784937).
2. Signal: the receptor switches on adenylate cyclase, an enzyme that makes the messenger molecule cAMP (PMID 6777774).
3. Enzyme step: in mouse melanoma cells, this raised the activity of tyrosinase, the key enzyme in melanin production (PMID 6777774).
4. Pigment output: reviews describe a shift toward eumelanin, the brown-black pigment type (PMID 38784937).

What laboratory (in vitro) research reports

In vitro means “in glass”: tests in cells, tissues or test tubes, not in living animals or people. For melanotan 1, the main in vitro findings are:

• Enzyme resistance: the analogue resisted breakdown by serum enzymes, unlike natural α-MSH (PMID 6777774).
• cAMP signalling: about 26 times the potency of α-MSH in activating mouse melanoma adenylate cyclase (PMID 6777774).
• Tyrosinase: raised tyrosinase activity in mouse melanoma cells (PMID 6777774).
• Receptor selectivity: highest affinity at MC1R, then MC3R, then MC5R (PMID 7774675).
• Tool compound: because it binds tightly and lasts, a radio-labelled form ([125I]NDP-MSH) became a standard probe for mapping melanocortin receptors in tissues (PMID 9564844).

What animal research reports

The earliest whole-tissue work used frog skin, a classic test for melanocyte hormones. Melanotan 1 darkened frog skin, and the effect lasted much longer than with natural α-MSH (PMID 6777774).

Later animal and tissue studies mostly used the peptide as a tool. For example, radio-labelled melanotan 1 was used to find MC5R binding sites in rat glands and tissues (PMID 9564844). In this kind of work, melanotan 1 is the measuring stick, not the subject of the study.

Animal findings do not show what happens in humans. Species differ in receptor make-up and in how they process peptides.

Human evidence for melanotan 1 (clinical trials)

Unlike many research peptides, melanotan 1 has published controlled human trials. All were run by clinical teams with medical oversight, ethics approval and pharmaceutical-grade material. The table groups them by type.

The phase 3 programme was published in the New England Journal of Medicine (DOI 10.1056/NEJMoa1411481). It used a 16 mg slow-release implant, not a research-grade powder. These results describe a specific approved formulation under prescription. They do not describe research-grade melanotan 1 peptide.

What the evidence does not establish

Good research writing says what is unknown, not just what is known. For melanotan 1, the published record does not establish:

• Safety of research-grade material in people. Trials used pharmaceutical-grade product made under drug manufacturing rules. Research-grade peptide is a different supply chain.
• Any use outside the approved label. Regulators approved one implant for one rare condition, on the basis of specific trials (NDA 210797).
• Long-term outcomes of non-supervised use. No controlled trials cover this.
• Equivalence with Melanotan 2. The two peptides differ in structure, and their data cannot be swapped (PMID 16412534).
• Animal-to-human transfer. Frog skin and rodent tissue results do not predict human responses.

Melanotan 1 research and regulatory status

Status checked on 16 October 2026.

• European Union: the European Commission authorised an afamelanotide implant on 22 December 2014, under “exceptional circumstances” because full data were hard to collect for such a rare disease (EMA EPAR).
• United States: the FDA approved an afamelanotide subcutaneous implant on 8 October 2019 under NDA 210797 (Drugs@FDA). It is a prescription product for adults with a specific rare light-sensitivity disorder.
• Research-grade melanotan 1: sold as a laboratory reagent only. It is not an approved drug, food, supplement or cosmetic, and it is not for human or veterinary use.

Analytical testing and storage considerations for melanotan 1

For any research peptide, the paperwork matters as much as the vial. A useful certificate of analysis (COA) for a melanotan 1 peptide should show:

• Identity by mass spectrometry (LC-MS): the measured mass should match the expected molecular weight of about 1646.8 g/mol (PubChem CID 16197727).
• Purity by RP-HPLC: a chromatogram with one main peak and a stated purity percentage.
• Content: the measured amount of peptide per vial, not only the label amount.
• Lot number and test date: so the report can be matched to the exact batch.
• Lab name and a way to verify: an independent laboratory and a verification code.

Two structure facts are useful when reading a COA for this peptide. The norleucine at position 4 replaces methionine, so the molecule has no methionine to oxidise. The D-phenylalanine at position 7 is a chiral (mirror-image) residue, so a high-quality identity check confirms the correct isomer, not just the correct mass.

Lyophilised (freeze-dried) peptides are usually stored cold, dry and away from light, following the supplier’s label. Always follow the storage line on the vial label and the COA.

Buy melanotan 1 for research: what to check

Many searches for “buy melanotan 1” or “melanotan 1 for sale” come from people outside a lab setting. Research-grade peptide is for qualified laboratory work only. It is not for people, pets or self-use.

Peplogy does not list melanotan 1 at the moment. If you buy melanotan 1 online from any research supplier, check for:

• a lot-specific COA from an independent lab, with LC-MS identity and HPLC purity;
• the correct name and sequence on the label (melanotan 1 is linear; melanotan 2 is cyclic);
• a clear research-use-only statement, and no health or cosmetic claims;
• a real business with contact details and a published returns policy.

You can see how Peplogy presents its own lab reports in the Peplogy COA library.

Melanotan 1 timeline

Melanotan 1 compared with related peptides

References

1. Sawyer TK, et al. 4-Norleucine, 7-D-phenylalanine-α-melanocyte-stimulating hormone: a highly potent α-melanotropin with ultralong biological activity. Proc Natl Acad Sci USA. 1980;77(10):5754-5758. PMID 6777774. DOI 10.1073/pnas.77.10.5754.
2. Levine N, et al. Induction of skin tanning by subcutaneous administration of a potent synthetic melanotropin. JAMA. 1991. PMID 1658407. DOI 10.1001/jama.1991.03470190078033.
3. Characterisation of melanocortin receptor subtypes by radioligand binding analysis. Eur J Pharmacol. 1995. PMID 7774675. DOI 10.1016/0922-4106(95)90043-8.
4. Skin pigmentation and pharmacokinetics of melanotan-I in humans. Biopharm Drug Dispos. 1997. PMID 9113347.
5. Selective properties of C- and N-terminals and core residues of the melanocyte-stimulating hormone on binding to the human melanocortin receptor subtypes. Eur J Pharmacol. 1998. PMID 9671118.
6. Expression of melanocortin-5 receptor in secretory epithelia. Endocrinology. 1998. PMID 9564844.
7. Pharmacologic response of a controlled-release PLGA formulation for Melanotan-I. Pharm Res. 2000. PMID 10888312.
8. Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006. PMID 16412534.
9. Lim HW, et al. Afamelanotide and narrowband UV-B phototherapy for vitiligo: a randomized multicenter trial. JAMA Dermatol. 2015. PMID 25230094.
10. Langendonk JG, et al. Afamelanotide for erythropoietic protoporphyria. N Engl J Med. 2015;373(1):48-59. PMID 26132941. NCT01605136, NCT00979745.
11. ACTH receptor (MC2R) specificity: what do we know about underlying molecular mechanisms? Front Endocrinol. 2017. PMID 28220105.
12. Afamelanotide in protoporphyria and other skin diseases: a review. Postepy Dermatol Alergol. 2024. PMID 38784937.
13. PubChem CID 16197727 (afamelanotide); EMA EPAR for afamelanotide implant; FDA Drugs@FDA NDA 210797.

Research-use notice

This article is for education and laboratory reference only. It is not medical advice. Research peptides sold by Peplogy are for in vitro laboratory research by qualified professionals. They are not for human or veterinary use, and they are not drugs, foods, supplements or cosmetics. Nothing here suggests that any compound is safe or effective for any use in people or animals.

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