# Melanotan I (Afamelanotide) — Research Peptide Profile

> Research guide to Melanotan I (afamelanotide) - the MC1R-selective alpha-MSH analog FDA-approved as Scenesse for erythropoietic protoporphyria.

Source: https://peptpedia.org/peptide/melanotan-i | Published: 2026-07-18 | Last updated: 2026-07-18

## Overview

Melanotan I (afamelanotide, [Nle4,D-Phe7]-alpha-MSH) is a linear 13-amino-acid analog of alpha-melanocyte stimulating hormone developed at the University of Arizona in the 1980s melanocortin program that also produced Melanotan II and PT-141. Substituting norleucine at position 4 and D-phenylalanine at position 7 makes it resistant to oxidation and enzymatic breakdown and markedly more potent than native alpha-MSH. Unlike the cyclic, non-selective Melanotan II, afamelanotide acts predominantly through the melanocortin-1 receptor (MC1R) on melanocytes, driving eumelanin production without the sexual and appetite effects of MC3R/MC4R activation. It became the only melanocortin tanning peptide to win regulatory approval: in 2019 the FDA approved it as Scenesse, a 16 mg subcutaneous implant, for adults with erythropoietic protoporphyria (EPP), a genetic disorder in which sunlight triggers excruciating phototoxic reactions.

## Molecular Profile

- **Category:** metabolic
- **Molecular formula:** C78H111N21O19
- **Molecular weight:** 1,646.8 g/mol
- **CAS number:** 75921-69-6
- **Amino acid sequence:** Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2
- **Also known as:** Afamelanotide, MT-I, MT-1, NDP-MSH, [Nle4,D-Phe7]-alpha-MSH, Scenesse, CUV1647
- **Half-life:** Beta-phase half-life 0.8-1.7 hours after subcutaneous injection of the free peptide; the slow-release 16 mg implant sustains clinical effect over the approximately 60-day dosing interval
- **Solubility:** Water-soluble linear peptide
- **Storage:** Store lyophilized peptide at -20°C protected from light; the marketed implant is stored refrigerated per its label.

## Mechanism of Action

Afamelanotide is an agonist of the melanocortin-1 receptor (MC1R), a Gs-coupled receptor expressed on epidermal melanocytes. Receptor activation raises intracellular cAMP, triggering the PKA-CREB-MITF signaling cascade that upregulates tyrosinase and the melanogenic enzyme program, increasing synthesis and epidermal deposition of eumelanin, the dark, photoprotective form of melanin. In erythropoietic protoporphyria, accumulated protoporphyrin IX in skin absorbs visible light and generates the reactive oxygen species behind painful phototoxic reactions; a denser melanin shield absorbs and scatters incoming light, raising the exposure threshold needed to provoke injury. Because the free peptide's beta-phase half-life is only 0.8-1.7 hours, the marketed product is a slow-release subcutaneous implant delivering 16 mg over roughly 60 days, producing sustained receptor stimulation and progressive pigmentation between doses.

## Key Research Findings

- Afamelanotide is the only melanocortin tanning peptide with regulatory approval: FDA-approved in 2019 as Scenesse, a 16 mg subcutaneous implant, for adults with erythropoietic protoporphyria.
- In two Phase 3 trials, afamelanotide increased pain-free sun exposure (69.4 versus 40.8 hours in the US study; 6.0 versus 0.8 hours in the EU study) and reduced phototoxic reactions from 146 to 77.
- Melanotan I is a linear alpha-MSH analog acting predominantly at MC1R, unlike the cyclic, non-selective Melanotan II, which activates all five melanocortin receptors.
- The free peptide's half-life is under 2 hours, so the approved product is a slow-release implant dosed every 2 months; diffuse hyperpigmentation occurs in almost all treated patients.

## Afamelanotide Pharmacokinetics: From a One-Hour Peptide to a 60-Day Implant

Melanotan I has one of the most completely mapped route-dependence profiles of any melanocortin peptide: human pharmacokinetic trials established that subcutaneous dosing is fully bioavailable while oral dosing produces no detectable drug, and the free peptide's short plasma half-life directly motivated the controlled-release implant that became the FDA-approved product Scenesse.

### Route Determines Exposure

The foundational pharmacokinetic trial compared three routes of administration in the same volunteers.

- Complete Subcutaneous Bioavailability: In a randomized three-way crossover in three male volunteers (0.16 mg/kg intravenously and orally; 0.08-0.21 mg/kg subcutaneously over two five-day dosing weeks), subcutaneous melanotan-I was completely bioavailable relative to intravenous dosing, while oral dosing produced no detectable plasma levels (PMID 9113347).
- Short Plasma Half-Life: After subcutaneous injection, absorption-phase half-lives ranged from 0.07 to 0.79 hours and beta-phase half-lives from 0.8 to 1.7 hours, with clearance of 0.12-0.19 L/kg/h and 3.9% or less of the dose recovered in urine (PMID 9113347).
- Oral and Transdermal Failure Confirmed: Review of the full clinical record confirms that neither oral nor transdermal application produced measurable plasma concentrations or a pigmentation response — subcutaneous delivery is the only effective non-invasive route for the free peptide (PMID 28063031).

### Effect Outlasts Plasma Presence

The clinical effect is decoupled from plasma concentration because newly synthesized melanin persists after the peptide itself is gone.

- Delayed Peak Effect: Tanning of the forehead, arms, and neck peaked one week after administration rather than at peak plasma concentration, and remained evident three weeks after completion of the ten-dose regimen (PMID 9113347).
- Cumulative Pharmacodynamics: Ten daily subcutaneous doses of 0.08-0.21 mg/kg produced long-lasting skin pigmentation — the clinical endpoint integrates cumulative MC1R stimulation and eumelanin deposition, not moment-to-moment drug levels (PMID 28063031).
- Response Across Genotypes: Two volunteer trials found that neither MC1R loss-of-function variants nor fair skin abolished the afamelanotide-induced increase in pigmentation, indicating the exposure-effect relationship holds across the common responder phenotypes (PMID 28063031).

### The Implant Solution

A peptide cleared within two hours but needed for months of photoprotection required a formulation fix, which became the approved product.

- Controlled-Release Rationale: A controlled-release formulation was developed specifically to optimize administration in humans and proved effective at a lower total dose than the daily saline injection regimens (PMID 28063031).
- Phase 3 Implant Schedule: The two pivotal EPP trials used 16 mg subcutaneous implants administered every 60 days, producing median pain-free direct sun exposure of 69.4 versus 40.8 hours in the US study and 6.0 versus 0.8 hours in the EU study against placebo (PMID 26132941).
- From Hours to Months: The implant converts a beta-phase half-life of 0.8-1.7 hours into a two-month dosing interval by slow release from a solid biodegradable rod — the formulation pharmacokinetics on which the 2019 FDA approval of Scenesse rests (PMID 9113347).

## Dosing Information (Research Context)

The approved product, Scenesse, is a 16 mg subcutaneous implant administered every 2 months in adults with erythropoietic protoporphyria; the Phase 3 trials used implants every 60 days. Early Phase 1 tanning studies used daily subcutaneous injections of 0.08-0.16 mg/kg for 10 days. Unregulated 'Melanotan' products sold online are not pharmaceutical afamelanotide and have no dosing standard.

| Route | Dose | Frequency | Notes |
| --- | --- | --- | --- |
| Subcutaneous implant (Scenesse) | 16 mg | Every 2 months | FDA-approved (2019) for adults with EPP and a history of phototoxic reactions |
| Subcutaneous injection (Phase 1 research) | 0.08–0.16 mg/kg/day | Daily for 10 days | Historical tanning studies; superseded by the implant formulation |

## Researched Effects

- **Photoprotection in Erythropoietic Protoporphyria** (evidence: extensive): Two multicenter, randomized, double-blind, placebo-controlled Phase 3 trials (Langendonk et al., NEJM 2015) tested 16 mg afamelanotide implants given every 60 days in 74 European and 94 American EPP patients. In the US study, median pain-free direct sun exposure after 6 months was 69.4 hours with afamelanotide versus 40.8 hours with placebo (P=0.04); in the European study after 9 months it was 6.0 versus 0.8 hours (P=0.005), and the number of phototoxic reactions fell from 146 on placebo to 77 on afamelanotide (P=0.04). Quality of life improved on validated questionnaires in both trials, adverse events were mostly mild, and no serious adverse events were attributed to the drug, the evidence base behind the 2019 FDA approval.
- **Melanogenesis and Tanning** (evidence: extensive): Phase 1 studies established afamelanotide's pigmentary pharmacology in humans. In three trials combining the peptide with UV-B or sunlight (Dorr et al., 2004), tanning was enhanced synergistically, subjects showed 47% fewer sunburn cells at an irradiated site, and sunlight-only controls required 50% more sun-exposure time to achieve equivalent tanning, with peptide-assisted tans persisting at least 3 weeks longer. Earlier pharmacokinetic work documented significant tanning of the forehead, arms, and neck after intravenous or subcutaneous dosing even without deliberate UV exposure, peaking one week after administration and persisting three weeks beyond a ten-dose regimen.
- **Quality of Life and Tolerability in EPP** (evidence: moderate): EPP patients typically organize their lives around light avoidance, and both Phase 3 trials recorded improved quality-of-life scores on afamelanotide alongside the increase in pain-free exposure. Tolerability across the program was favorable: adverse events were mostly mild, serious events were judged unrelated to study drug, and earlier Phase 1 work reported only nausea, transient facial flushing, and occasional gastrointestinal upset. Review of the broader clinical literature notes diffuse hyperpigmentation in almost all treated patients, the expected on-target effect of MC1R agonism, with no serious adverse effects reported to date.
- **Broader Dermatologic Research** (evidence: moderate): Beyond EPP, afamelanotide has randomized controlled trial evidence in polymorphic light eruption and in vitiligo, where MC1R-driven repigmentation complements phototherapy, and smaller studies report efficacy in acne vulgaris, Hailey-Hailey disease, and solar urticaria. These applications exploit the same photoprotective and anti-inflammatory melanocortin biology, though reviewers emphasize that larger trials are needed and that pediatric safety, efficacy, and dosing remain undetermined.
- **Implant Sustained-Release Pharmacology** (evidence: moderate): Comparative pharmacokinetic trials showed subcutaneous afamelanotide is essentially completely bioavailable relative to intravenous dosing, with a beta-phase half-life of 0.8-1.7 hours, while oral dosing produced no detectable plasma levels. That short free-drug half-life motivated the slow-release implant formulation: a single 16 mg rod inserted subcutaneously maintains drug delivery and biological effect over the 60-day dosing interval used in the EPP trials and specified in the approved label.

## Research Applications

- Photodermatosis Research
- Melanocortin Pharmacology
- Dermatology
- Vitiligo Research
- Photoprotection Studies

## Key Studies

### Afamelanotide for Erythropoietic Protoporphyria

Langendonk JG, Balwani M, Anderson KE, et al. — *New England Journal of Medicine* (2015) — [PMID 26132941](https://pubmed.ncbi.nlm.nih.gov/26132941/) | [doi:10.1056/NEJMoa1411481](https://doi.org/10.1056/NEJMoa1411481)

Two multicenter, randomized, double-blind, placebo-controlled trials evaluated subcutaneous implants containing 16 mg of afamelanotide, given every 60 days, in 74 European Union and 94 United States EPP patients. Median pain-free direct sun exposure was longer on afamelanotide in both studies (US: 69.4 versus 40.8 hours at 6 months, P=0.04; EU: 6.0 versus 0.8 hours at 9 months, P=0.005), and the EU study recorded fewer phototoxic reactions (77 versus 146, P=0.04). Quality of life improved with treatment in both trials; adverse events were mostly mild and serious events were not considered drug-related. These results underpinned regulatory approval of afamelanotide for EPP.

### Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers

Dorr RT, Ertl G, Levine N, et al. — *Archives of Dermatology* (2004) — [PMID 15262693](https://pubmed.ncbi.nlm.nih.gov/15262693/) | [doi:10.1001/archderm.140.7.827](https://doi.org/10.1001/archderm.140.7.827)

Three Phase 1 studies examined melanotan-1 ([Nle4,D-Phe7]-alpha-MSH, 0.08-0.16 mg/kg/day subcutaneously) combined with UV-B light or sunlight in human volunteers. Tanning was achieved in 3 of 4 subjects in the first study, with 47% fewer sunburn cells at the UV-irradiated site; higher doses darkened more skin sites in the second; and in the third, peptide-treated subjects tanned significantly more than sunlight-only controls, maintained the tan at least 3 weeks longer, and controls needed 50% more sun-exposure time for equivalent tanning. Toxicity was minor, limited to nausea and transient facial flushing, supporting synergy between the peptide and UV exposure.

### Skin pigmentation and pharmacokinetics of melanotan-I in humans

Ugwu SO, Blanchard J, Dorr RT, et al. — *Biopharmaceutics & Drug Disposition* (1997) — [PMID 9113347](https://pubmed.ncbi.nlm.nih.gov/9113347/) | [doi:10.1002/(sici)1099-081x(199704)18:3<259::aid-bdd20>3.0.co;2-x](https://doi.org/10.1002/(sici)1099-081x(199704)18:3<259::aid-bdd20>3.0.co;2-x)

This comparative pharmacokinetic trial gave melanotan-I intravenously, orally, and subcutaneously (0.08-0.21 mg/kg) to three male volunteers over two five-day dosing weeks. Subcutaneous dosing was completely bioavailable relative to IV, oral dosing produced no detectable drug, and beta-phase half-lives ranged from 0.8 to 1.7 hours with 3.9% or less recovered in urine. Significant tanning of the forehead, arms, and neck followed IV or SC dosing, peaking one week after administration and persisting three weeks beyond the regimen. Side effects were minimal (occasional gastrointestinal upset and facial flushing), establishing subcutaneous delivery as the effective route and the rationale for a long-acting formulation.

### Afamelanotide: An Orphan Drug with Potential for Broad Dermatologic Applications

Wu J, Cotliar R — *Journal of Drugs in Dermatology* (2021) — [PMID 33683075](https://pubmed.ncbi.nlm.nih.gov/33683075/) | [doi:10.36849/JDD.5526](https://doi.org/10.36849/JDD.5526)

This review of the afamelanotide literature and trial registry confirms its status as FDA-approved (Scenesse) to increase pain-free sunlight exposure in adults with erythropoietic protoporphyria, and surveys its wider dermatologic potential. Randomized controlled trial evidence exists for polymorphic light eruption and vitiligo, and smaller studies report benefit in acne vulgaris, Hailey-Hailey disease, and solar urticaria. The authors note that no serious adverse effects have been reported, though diffuse hyperpigmentation occurs in almost all patients, and call for larger trials and dedicated pediatric safety and dosing research.

## Frequently Asked Questions

### What is the difference between Melanotan I and Melanotan II?

Melanotan I (afamelanotide) is a linear 13-amino-acid alpha-MSH analog acting predominantly at MC1R, the melanocyte pigmentation receptor. Melanotan II is a smaller cyclic analog that non-selectively activates MC1R through MC5R, adding sexual arousal, appetite suppression, and nausea to the pigmentary effect. The practical difference is regulatory: afamelanotide completed Phase 3 trials and is FDA-approved as Scenesse for erythropoietic protoporphyria, while Melanotan II was never approved anywhere and remains an unregulated research compound.

### Is Melanotan I FDA-approved?

Yes, in a specific form. The FDA approved afamelanotide in 2019 under the brand name Scenesse: a 16 mg subcutaneous implant indicated to increase pain-free light exposure in adult patients with a history of phototoxic reactions from erythropoietic protoporphyria. Approval applies only to that implant product and indication. Bulk 'Melanotan I' sold as a research chemical carries no approval, and compounded or online versions are not the reviewed product.

### How does afamelanotide help in erythropoietic protoporphyria?

In EPP, defective ferrochelatase causes protoporphyrin IX to accumulate in skin and blood. Daylight excites the protoporphyrin, generating reactive oxygen species that produce immediate, severe burning pain. Afamelanotide activates MC1R on melanocytes to increase epidermal eumelanin, which absorbs and scatters incoming light before it reaches protoporphyrin-rich tissue, raising the threshold for phototoxic injury. In the Phase 3 trials this translated into significantly more pain-free sun exposure (69.4 versus 40.8 hours in the US study) and fewer phototoxic reactions.

### What is the afamelanotide implant and why is it needed?

Scenesse is a rice-grain-sized solid rod containing 16 mg of afamelanotide, inserted subcutaneously, typically in the hip area, where it dissolves slowly. The implant exists because the free peptide's pharmacokinetics are poor for chronic therapy: subcutaneous afamelanotide has a beta-phase half-life of only 0.8-1.7 hours. Sustained release over the 2-month dosing interval maintains MC1R stimulation and progressive pigmentation between administrations, which daily injections could not practically achieve.

### Does Melanotan I tan skin without sun exposure?

Yes, pharmacologically. In the Ugwu pharmacokinetic study, significant tanning of the forehead, arms, and neck followed intravenous or subcutaneous dosing without any deliberate UV exposure, peaking a week after dosing. The Dorr Phase 1 studies then showed the peptide acts synergistically with UV: treated subjects developed deeper, longer-lasting tans with less sun and had 47% fewer sunburn cells at irradiated sites. The tan is a direct drug effect on melanocytes, not incidental bronzing.

### What side effects does afamelanotide have?

The recorded profile is mild relative to most approved drugs. Phase 1 studies reported nausea, transient facial flushing, and occasional gastrointestinal upset. In the Phase 3 EPP trials, adverse events were mostly mild and no serious adverse events were attributed to the drug. Review of the wider literature notes diffuse hyperpigmentation in almost all treated patients, an on-target effect that is desirable in EPP but relevant for anyone considering cosmetic use, and long-term pediatric safety remains unstudied.

### Is 'Melanotan' bought online the same as afamelanotide?

No. Online 'Melanotan' products are unregulated research chemicals of unknown identity, dose, and purity, and many actually contain Melanotan II, the non-selective cyclic analog with a broader side-effect profile. Pharmaceutical afamelanotide exists only as the Scenesse implant, administered by clinicians to EPP patients under its approved program. Regulators in multiple countries have warned against injectable tanning products precisely because they are not equivalent to the approved drug.

### What else has afamelanotide been studied for?

A 2021 literature review identified randomized controlled trial evidence for afamelanotide in polymorphic light eruption, another photosensitivity disorder, and in vitiligo, where MC1R-driven melanocyte stimulation is combined with phototherapy to encourage repigmentation. Smaller studies report benefit in acne vulgaris, Hailey-Hailey disease, and solar urticaria. The reviewers stress that these indications rest on limited trial numbers and that larger confirmatory studies are needed.

## Related Peptides

- [Melanotan II](https://peptpedia.org/peptide/melanotan-ii)
- [PT-141](https://peptpedia.org/peptide/pt-141)
- [Kisspeptin](https://peptpedia.org/peptide/kisspeptin)

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