Try Calculator
← Back to Compound Library SKIN / COSMETIC

Melanotan 1 (MT-1)

A Comprehensive Research Review of Afamelanotide

Introduction and Overview

Melanotan 1 (MT-1), also known by its pharmaceutical name afamelanotide, is a synthetic analog of alpha-melanocyte stimulating hormone (α-MSH) that stimulates melanin production in the skin. Among the melanocortin-based peptides used for tanning and photoprotection, MT-1 stands out for its higher selectivity toward the melanocortin 1 receptor (MC1R) and its distinction as the only melanocortin analog to achieve regulatory approval from the United States Food and Drug Administration (FDA).

MT-1 was developed at the University of Arizona during the 1980s as part of a research effort to create a practical sunless tanning agent. Scientists understood that α-MSH was the primary trigger of melanogenesis—the process by which the skin produces melanin—but the natural hormone was far too unstable and short-lived for therapeutic use. By modifying key amino acid residues in the α-MSH sequence, researchers created MT-1, a peptide reported to be approximately 1,000 times more potent and significantly more stable than native α-MSH.

In October 2019, the FDA approved MT-1 under the brand name Scenesse (manufactured by Clinuvel Pharmaceuticals) for the treatment of erythropoietic protoporphyria (EPP), a rare genetic disorder causing extreme sensitivity to light. The approved formulation is a 16 mg subcutaneous implant that releases the peptide over approximately 60 days. Scenesse had previously received European Medicines Agency (EMA) approval in 2014, and it is also approved in Australia and other regions for the same indication.

Compared to its structural relative Melanotan 2 (MT-2), MT-1 offers a more selective pharmacological profile. While both peptides produce skin darkening, MT-1 focuses primarily on melanogenesis through MC1R activation without the broader effects on sexual function, appetite, and other systems that MT-2 produces through its less selective receptor binding. This selectivity translates into fewer off-target side effects and a cleaner overall safety profile, which contributed to its successful passage through the regulatory approval process.

How It Works

MT-1 exerts its primary effects through activation of the melanocortin 1 receptor (MC1R) on melanocytes, the specialized cells in the skin responsible for producing melanin. Understanding the mechanism of action requires an appreciation of both the receptor pharmacology and the downstream signaling cascade.

MC1R Activation and Melanogenesis

When MT-1 binds to MC1R on the surface of melanocytes, it triggers a well-characterized intracellular signaling cascade. MC1R is a G-protein coupled receptor that, upon activation, stimulates adenylyl cyclase to increase intracellular cyclic AMP (cAMP) levels. Elevated cAMP activates protein kinase A (PKA), which in turn phosphorylates the cAMP response element- binding protein (CREB). Phosphorylated CREB upregulates the expression of microphthalmia- associated transcription factor (MITF), the master regulator of melanocyte function. MITF then drives the expression of enzymes critical to melanin synthesis, including tyrosinase, tyrosinase- related protein 1 (TRP-1), and dopachrome tautomerase (TRP-2).

The net result of this signaling cascade includes significantly increased melanin synthesis, distribution of melanin to surrounding keratinocytes (the primary structural cells of the skin), gradual and progressive darkening of the skin, and an enhanced protective melanin layer that reduces ultraviolet (UV) radiation damage. Importantly, MT-1 preferentially promotes the production of eumelanin (the brown-black pigment) rather than pheomelanin (the red-yellow pigment associated with increased oxidative damage and lesser photoprotection). This eumelanin-favoring profile is particularly relevant for fair-skinned individuals, who naturally produce a higher proportion of pheomelanin.

Receptor Selectivity Advantage

The key pharmacological distinction between MT-1 and MT-2 lies in receptor selectivity. MT-2 activates multiple melanocortin receptors, including MC1R, MC3R, MC4R, and MC5R, each of which mediates different physiological effects. MC4R activation, for example, is responsible for the appetite-suppressing and sexual arousal effects associated with MT-2.

MT-1, by contrast, binds with significantly higher selectivity for MC1R. This translates into a more focused effect on pigmentation, minimal impact on appetite regulation (an MC4R-mediated effect), minimal sexual side effects (also MC4R-mediated), and a cleaner and more predictable side effect profile overall.

Mechanism of Photoprotection

The increased melanin production stimulated by MT-1 provides a form of natural photoprotection through several overlapping mechanisms. Eumelanin absorbs UV radiation across a broad spectrum, converting photon energy into heat through a process known as ultrafast internal conversion. It reduces the formation of DNA-damaging reactive oxygen species (ROS) by scavenging free radicals. It decreases the formation of sunburn cells (apoptotic keratinocytes resulting from UV-induced DNA damage), and it provides a baseline layer of protection before any sun exposure occurs.

Clinical trial data demonstrated that subjects treated with MT-1 had 47% fewer sunburn cells compared to untreated controls following equivalent UV exposure, underscoring the functional significance of MT-1-induced melanin production.

Pharmacokinetics

MT-1 has a very short intrinsic half-life of approximately 30 minutes following subcutaneous injection, which limits its utility as a stand-alone injectable. This pharmacokinetic challenge is the reason the FDA-approved formulation uses a controlled-release subcutaneous implant. The implant provides an apparent half-life of approximately 15 hours, with a median time to peak concentration (Tmax) of 36 hours. Pigmentary effects persist for weeks after administration, as the melanin produced during the active drug exposure period remains in the skin through normal turnover cycles.

Research Benefits

Sunless Tanning and Skin Darkening

The most extensively studied and well-established benefit of MT-1 is its ability to induce skin darkening with reduced reliance on UV radiation. Research has demonstrated that MT-1 develops a visible tan with minimal UV exposure, produces deep, natural-looking pigmentation through eumelanin induction, is effective for fair-skinned individuals (Fitzpatrick skin types I and II) who typically burn rather than tan, and generates tanning effects that persist for weeks after the treatment period ends. While some degree of UV exposure accelerates and deepens the tanning response, MT-1 can produce measurable increases in melanin density even without UV exposure, distinguishing it from conventional tanning mechanisms that are entirely UV- dependent.

Ultraviolet Radiation Protection

The increased melanin produced by MT-1 provides meaningful protection against UV radiation damage. Studies have shown reduced sunburn severity following UV exposure, significant reductions in sunburn cell formation, a natural “sunscreen” effect from elevated eumelanin, and synergistic protective effects when combined with moderate sun exposure. This photoprotective effect is of particular interest for populations at elevated risk of UV-induced skin damage, including individuals with fair skin, those with outdoor occupational exposure, and those living in high-UV-index regions.

Erythropoietic Protoporphyria (EPP) Treatment

The FDA-approved indication for MT-1 is the treatment of EPP, a rare inherited disorder in which a deficiency of the ferrochelatase enzyme leads to the accumulation of protoporphyrin IX in the blood and skin. This causes severe, incapacitating phototoxic reactions upon exposure to visible light. Clinical trials have demonstrated that MT-1 significantly increases the duration of pain-free sun exposure, reduces the frequency and severity of phototoxic reactions, dramatically improves quality of life as measured by validated questionnaires, and enables patients to engage in outdoor activities that would otherwise be impossible. EPP patients treated with afamelanotide reported quality of life scores increasing from approximately 31% of maximum at baseline to approximately 74% during treatment.

Potential Applications Under Investigation

Beyond its approved indication, MT-1 is being investigated for several additional applications. Research suggests potential benefits in vitiligo, where MT-1 combined with narrowband UVB (NB-UVB) phototherapy has shown faster and more complete repigmentation compared to phototherapy alone. Studies have also examined MT-1 for polymorphic light eruption, where it may reduce the frequency and severity of reactions, as well as for solar urticaria and general photoprotection for individuals at elevated risk of UV-induced skin cancer.

What the Science Shows

MT-1 has the most extensive clinical evidence base of any tanning peptide, including the rigorous clinical trial program that supported its FDA approval.

Phase 1 Trials — University of Arizona (Dorr et al., 2004) Three phase 1 clinical trials were conducted at the Arizona Health Sciences Center to evaluate the safety and tanning efficacy of MT-1 in combination with UV exposure. These open-label studies administered MT-1 at doses of 0.08 to 0.16 mg/kg per day subcutaneously for 10 days combined with controlled UV-B or sunlight exposure. Results showed that treated subjects had 47% fewer sunburn cells at irradiated sites, significantly enhanced tanning compared to sunlight- only controls, tanning responses that persisted at least three weeks longer than those of controls, and side effects limited to mild, transient nausea and facial flushing. Notably, control subjects required 50% more sun exposure time to achieve equivalent tanning, and the 0.16 mg/kg dose was found to be superior to the 0.08 mg/kg dose without producing cumulative or new adverse effects.

EPP Phase 3 Trials (Langendonk et al., 2015) The pivotal trials that formed the basis for FDA approval comprised two multicenter, randomized, double-blind, placebo-controlled studies conducted in the European Union (74 patients) and the United States (94 patients). A total of 244 adults with EPP were enrolled across three clinical trials. Subjects received a 16 mg subcutaneous implant of afamelanotide or placebo every 60 days. In the U.S. trial, the median duration of pain-free sun exposure after six months was 69.4 hours in the afamelanotide group compared to 40.8 hours in the placebo group. In the EU trial, the duration of pain-free time after nine months was 6.0 hours versus 0.8 hours, and the number of phototoxic reactions was significantly lower in the treatment group (77 versus 146 events). Quality of life improved significantly in both trials, and the safety profile was favorable with mostly mild adverse events.

Vitiligo Trial (Lim et al., 2015) A multicenter randomized trial evaluated the combination of MT-1 implant with narrowband UVB (NB-UVB) phototherapy versus NB-UVB phototherapy alone for the treatment of vitiligo. Results demonstrated faster and superior repigmentation with the combination treatment compared to phototherapy alone. The combination was particularly effective on the face and upper extremities, areas that typically respond well to melanocortin stimulation. This study highlights a potential off-label application for MT-1 that leverages its melanocyte-activating properties in depigmented skin.

Long-Term Observational Data (Haylett et al., 2020; Biolcati et al., 2015) Long-term observational studies, including data from up to eight years of follow-up in EPP patients, have provided reassuring safety and efficacy information. These studies found no serious adverse events attributable to afamelanotide over extended use, sustained benefit and maintained quality of life improvements over time, phototoxic burn tolerance increases of 1.8- fold to 180-fold depending on the measurement protocol, and high patient compliance with low discontinuation rates. Post-authorization safety study (PASS) data submitted to the FDA, including patients with up to 10 years of afamelanotide exposure, did not identify additional safety concerns beyond those observed in the controlled trials.

5. Dosing Protocol

MT-1 dosing differs from MT-2 due to its shorter half-life and the availability of an FDA- approved controlled-release implant formulation.

FDA-Approved Implant (Scenesse) The approved dosing regimen consists of a 16 mg subcutaneous implant administered every 60 days by a healthcare professional trained in the implantation procedure. The implant provides controlled release of afamelanotide over the dosing interval. The maximum approved dosing schedule is four implants per year. This formulation is specifically indicated for adults with EPP who have a history of phototoxic reactions.

Injectable Research Protocol

For research contexts using injectable formulations, more frequent dosing is required due to MT- 1’s short intrinsic half-life. Published research protocols have utilized the following general approach:

Phase Dose Frequency Duration Loading 0.25 mg Daily 10 days Protective 0.25 mg Before sun exposure As needed Maintenance 0.25–0.5 mg 1–2 times weekly Ongoing

Due to MT-1’s short half-life, effects build with consistent dosing over time. MT-1 typically requires higher and more frequent dosing than MT-2 to achieve comparable tanning effects because of its greater receptor selectivity and shorter duration of action.

Dosing Comparison to MT-2

MT-1 generally requires higher cumulative doses and more frequent administration than MT-2 to produce equivalent tanning. This is attributable to MT-1’s narrower receptor selectivity (focused on MC1R only), shorter half-life (approximately 30 minutes versus several hours for MT-2), and lower milligram-for-milligram potency for tanning. However, this dosing disadvantage is offset by MT-1’s significantly cleaner side effect profile.

UV Exposure Considerations

Moderate UV exposure accelerates the tanning response to MT-1. Research protocols have typically incorporated 15 to 30 minutes of sun exposure during the loading phase. Significantly less UV is needed compared to natural tanning to achieve visible results. The goal is gentle melanocyte activation, not sunburn. Patients using the approved Scenesse implant for EPP are instructed to maintain their existing sun protection measures.

Draw Volumes by Vial Size

For a 10 mg vial reconstituted with 2 mL of bacteriostatic water (yielding a concentration of 5 mg/mL):

Dose Volume Units on Syringe 0.25 mg 0.05 mL 5 units 0.50 mg 0.10 mL 10 units 1.0 mg 0.20 mL 20 units

At 0.25 mg daily for a 10-day loading phase, one 10 mg vial provides 40 doses, covering the loading phase plus substantial maintenance.

Reconstitution Instructions

1. Remove the plastic cap from the vial and wipe the rubber stopper with an alcohol swab. 2. Draw 2 mL of bacteriostatic water into a sterile syringe. 3. Insert the needle through the rubber stopper at an angle. 4. Direct the stream of water down the inside wall of the vial to avoid disturbing the lyophilized powder. 5. Allow the peptide to dissolve without shaking. 6. Gently swirl if needed until the solution is completely clear. 7. Label the vial with the date and concentration (5 mg/mL). MT-1 dissolves readily in bacteriostatic water. The reconstituted solution should be clear and colorless. Discard the vial if the solution appears cloudy or discolored.

Side Effects

Common Side Effects

The most frequently reported side effects in clinical trials of MT-1 include nausea (the most common, reported in approximately 19% of treated subjects versus 14% on placebo; typically mild and transient), facial flushing (temporary vasodilation, usually resolving within minutes to hours), headache, fatigue (reported in approximately 6% of treated subjects), injection site or implant site reactions (reported in 21% of implant recipients versus 10% on placebo), dizziness, and somnolence.

These side effects were predominantly mild to moderate in severity and transient in nature. In the pivotal clinical trials, few adverse events led to treatment discontinuation.

Skin-Related Effects

As an expected pharmacological consequence of increased melanogenesis, MT-1 produces generalized skin darkening (the intended therapeutic or cosmetic effect), darkening of existing moles (nevi) and freckles (ephelides), and possible development of new melanocytic nevi. The FDA prescribing information recommends full-body skin examinations twice yearly for patients receiving Scenesse, specifically to monitor for changes in existing nevi and the appearance of new pigmented lesions.

Advantages Over MT-2 Side Effect Profile

MT-1 demonstrates a meaningfully cleaner side effect profile compared to MT-2. Due to its higher MC1R selectivity, MT-1 produces minimal appetite suppression (unlike MT-2, which activates MC4R), minimal sexual side effects (MT-2 is known to cause spontaneous erections and increased libido through MC4R activation), and more predictable, dose-proportional effects. This difference in side effect profiles was a key factor in MT-1’s successful progression through regulatory approval, while MT-2 remains unapproved.

Theoretical and Long-Term Concerns

The most significant theoretical concern with any agent that stimulates melanocyte activity is the potential impact on melanoma risk. However, clinical trial data and long-term observational studies spanning up to 10 years of exposure have not demonstrated an increased risk of melanoma in MT-1-treated patients. The post-authorization safety studies required by the FDA as a condition of approval have not identified new safety signals. Nonetheless, ongoing monitoring of mole changes remains a prudent precaution, and the prescribing information includes appropriate warnings regarding skin surveillance.

Contraindications and Precautions

Absolute Contraindications

hypersensitivity reactions, including anaphylaxis, have been reported post-marketing)

show adverse developmental effects, but use is not recommended)

Relative Contraindications and Precautions

assessment)

unknown)

unknown)

Monitoring Recommendations

The FDA prescribing information for Scenesse recommends full-body skin examinations twice yearly during treatment. Any changes in existing moles—including changes in size, shape, color, or border irregularity—should be promptly evaluated by a dermatologist. Patients should also report any implant site reactions to their healthcare provider.

Comparison: MT-1 vs. MT-2

Understanding the differences between MT-1 and MT-2 is essential for evaluating the risk- benefit profile of each peptide.

Parameter Melanotan 1 (MT-1) Melanotan 2 (MT-2) Chemical Name Afamelanotide Ac-Nle-c[Asp-His-D-Phe-Arg-

Trp-Lys]-NH₂

Structure Linear tridecapeptide Cyclic heptapeptide Primary Receptor MC1R (selective) MC1R, MC3R, MC4R, MC5R FDA Approval Yes (Scenesse, 2019) No Half-Life ~30 min (intrinsic); ~15 hr ~2 hours (implant)

Tanning Potency Moderate (requires higher doses) High (lower doses effective) Sexual Side Effects Minimal Significant (MC4R activation) Appetite Effects Minimal Appetite suppression (MC4R) Safety Data Extensive clinical trial data Limited clinical data Formulation 16 mg implant (approved); Injectable only injectable Dosing Frequency Daily (injectable) or q60 days 2–3 times weekly (implant) Best Suited For Tanning, photoprotection, EPP Tanning, sexual dysfunction

In summary, MT-1 provides a more targeted approach to melanogenesis with a superior safety profile and regulatory backing, while MT-2 offers greater milligram-for-milligram potency and additional effects on sexual function and appetite that some users may find desirable but that increase the risk of off-target effects.

Success Tips

Consistency Is Critical

Due to MT-1’s short half-life, consistent daily dosing during the loading phase is essential for building sufficient melanin levels. Unlike MT-2, which has a longer half-life and can be dosed less frequently, MT-1 requires regular, disciplined administration to achieve optimal results.

Moderate UV Exposure Accelerates Results

While MT-1 can produce some degree of pigmentation without UV exposure, moderate sun exposure accelerates and deepens the tanning response. During the loading phase, 15 to 30 minutes of sun exposure is generally recommended. The objective is gentle melanocyte activation—not sunburn. Overexposure to UV negates the photoprotective benefit and increases skin damage risk.

Monitor Skin Before and During Use

Document the baseline appearance of all moles before initiating MT-1. Photograph any moles of concern. While clinical studies have demonstrated a favorable long-term safety profile, any changes in mole size, shape, color, or symmetry during treatment should be evaluated by a dermatologist. This applies regardless of whether the approved implant or research injectable is being used.

Set Realistic Expectations

Tanning effects from MT-1 develop more gradually than with MT-2. Users should expect visible results over two to four weeks of consistent dosing, rather than the more rapid onset sometimes

reported with MT-2. The trade-off for this slower onset is a more predictable, better-documented safety profile.

Storage and Handling

Before Reconstitution (Lyophilized Powder)

After Reconstitution

matter MT-1 dissolves readily in bacteriostatic water. The reconstituted solution should be clear and colorless. Proper aseptic technique should be observed during reconstitution and each withdrawal to prevent microbial contamination.

Legal Status

United States: MT-1 (afamelanotide) is FDA-approved under the brand name Scenesse for the treatment of EPP. It is a prescription medication for this specific indication. Sale and use for cosmetic tanning purposes are not FDA-approved. Research peptide versions are available from research chemical suppliers but are not approved for human use outside of the EPP indication.

European Union: Afamelanotide received marketing authorization from the European Medicines Agency in 2014 for the prevention of phototoxicity in adult patients with EPP. The European Commission granted approval, and it is available by prescription in EU member states for this indication.

Australia: Approved by the Therapeutic Goods Administration (TGA) for the treatment of EPP. Clinuvel Pharmaceuticals, the manufacturer, is headquartered in Melbourne, Australia.

Frequently Asked Questions

How is MT-1 different from MT-2?

MT-1 is more selective for MC1R (the pigmentation receptor) while MT-2 activates multiple melanocortin receptors including MC3R, MC4R, and MC5R. This means MT-1 produces tanning with minimal sexual or appetite-related effects, while MT-2 has broader systemic effects. MT-1 also has FDA approval and substantially more clinical safety data supporting its use.

Is MT-1 safer than MT-2?

MT-1 has a significantly better-documented safety profile due to its passage through controlled clinical trials and the FDA approval process. Its selective receptor binding produces fewer off- target effects. However, both compounds stimulate melanocyte activity and therefore share theoretical concerns regarding mole changes and the need for dermatological monitoring.

Why do I need to dose MT-1 more frequently than MT-2?

MT-1 has a much shorter intrinsic half-life (approximately 30 minutes versus approximately two hours for MT-2). The FDA-approved formulation addresses this through a controlled-release implant. For injectable use, frequent dosing is necessary to maintain therapeutically effective circulating levels.

Can MT-1 treat vitiligo?

MT-1 has shown promise for vitiligo repigmentation when combined with narrowband UVB phototherapy. Clinical trial results demonstrated faster and more complete repigmentation compared to phototherapy alone, particularly on the face and upper extremities. It is not a cure for vitiligo, but it may help restore pigmentation in affected areas by activating residual melanocytes.

Will MT-1 affect my libido?

Unlike MT-2, MT-1 has minimal effects on sexual function because it does not significantly activate MC4R, the melanocortin receptor subtype involved in sexual arousal pathways. Most clinical trial subjects and research users report no noticeable change in libido.

Is MT-1 the same as the FDA-approved drug Scenesse?

Yes. Afamelanotide is the active pharmaceutical ingredient in Scenesse. The difference lies in the formulation and regulatory status. Scenesse is the branded, FDA-approved 16 mg subcutaneous implant manufactured by Clinuvel Pharmaceuticals. Research-grade MT-1 peptide is chemically the same molecule but is not manufactured under the same pharmaceutical-grade conditions and is not approved for therapeutic use.

How long does it take to see tanning results from MT-1?

With consistent daily dosing during a loading phase, visible tanning typically becomes apparent over two to four weeks. This is slower than the onset commonly reported with MT-2, but the tanning effect is long-lasting and persists for weeks after discontinuation due to the stability of eumelanin in the skin.

13. References

1. Dorr RT, Ertl G, Levine N, et al. Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers. Archives of Dermatology. 2004;140(7):827–835. 2. Langendonk JG, Balwani M, Anderson KE, et al. Afamelanotide for erythropoietic protoporphyria. New England Journal of Medicine. 2015;373(1):48–59. 3. Lim HW, Grimes PE, Agbai O, et al. Afamelanotide and narrowband UV-B phototherapy for the treatment of vitiligo: a randomized multicenter trial. JAMA Dermatology. 2015;151(1):42–50. 4. Clinuvel Pharmaceuticals. SCENESSE (afamelanotide) Prescribing Information. U.S. Food and Drug Administration. 2019. 5. Haylett AK, Sherwood S, Baker CS, et al. Efficacy of afamelanotide for the long-term treatment of erythropoietic protoporphyria. JAMA Dermatology. 2020;156(12):1366– 1370. 6. Biolcati G, Marchesini E, Sorge F, et al. Long-term observational study of afamelanotide in 115 patients with erythropoietic protoporphyria. British Journal of Dermatology. 2015;172(6):1601–1612. 7. Barnetson RS, Ooi TKT, Zhuang L, et al. [Nle4-D-Phe7]-α-melanocyte-stimulating hormone significantly increased pigmentation and decreased UV damage in fair-skinned Caucasian volunteers. Journal of Investigative Dermatology. 2006;126(8):1869–1878. 8. Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006;27(4):921–930. 9. U.S. Food and Drug Administration. Drug Approval Package: SCENESSE (afamelanotide). NDA 210797. October 8, 2019.

Property Support

Our Property Support services are designed to help homeowners, property managers, and businesses maintain safe, clean, and well-functioning properties year-round.

Get In Touch