Melanotan I, known by the international name afamelanotide and the trade name Scenesse, stands out among all the melanocortin peptides for one reason: it is an approved medicine. The European Medicines Agency authorised it in December 2014 and the US FDA in October 2019 — in both cases for one rare skin disease, erythropoietic protoporphyria, and not “for a tan”. Behind that stand two randomised trials in the New England Journal of Medicine and follow-up reaching eight years. We set out what was shown, and correct two claims often repeated about this peptide: that it is selective for a single receptor, and that nausea is only a problem at the start.
What afamelanotide (Melanotan I) is
Afamelanotide is a synthetic counterpart of one of the body's own hormones — melanocyte-stimulating hormone, α-MSH for short. It was the first analogue of that hormone, synthesised as far back as 1980 (Minder et al., 2017). It was made by swapping two amino acids in the natural molecule, which makes it more stable and more potent — hence its descriptive chemical name, NDP-α-MSH. The name “Melanotan I” is historical and still used outside medicine; it comes from the same body of work that later produced Melanotan II, a molecule of different structure and a different profile of action.
One pharmacological fact matters here: the route of administration is not a question of convenience. In volunteer studies, subcutaneous delivery had full bioavailability, whereas neither oral nor transdermal delivery produced measurable plasma concentrations or any pigmentation response (Minder et al., 2017). Clinically, a sustained-release form is used — an implant containing 16 mg of the peptide, inserted under the skin.
How it works — the MC1R switch and pigment
Melanocytes, the pigment cells of the skin, carry a “switch” called the melanocortin-1 receptor (MC1R). Activating it turns on several things at once: melanin (pigment) production, antioxidant mechanisms, DNA repair and modulation of inflammation (Minder et al., 2017). Fair-skinned people often carry MC1R variants that respond poorly to the natural hormone — and this is an interesting point, because in two volunteer studies neither the gene variant nor fair skin reduced the rise in pigmentation after afamelanotide. The peptide gets the job done where the natural hormone is too weak.
In protoporphyria the defence is twofold: more melanin absorbs light before it reaches the substance accumulating in the skin (protoporphyrin IX), and antioxidant pathways switch on as well. The first study in patients (Harms et al., 2009) measured both ends of that chain: skin melanin density rose significantly above baseline (P = 0.004), and so did tolerance in a standardised photoprovocation test (P = 0.007).
Is it really selective
It is widely repeated that afamelanotide is a “selective MC1R agonist” that leaves the brain's MC4R receptor — the one behind nausea and autonomic effects — untouched. The data do not support this. In 2021, structures of the MC4R receptor captured in its active state together with afamelanotide were published, solved by cryo-electron microscopy at 2.9 angstrom resolution (Heyder et al.). The paper describes afamelanotide as “a high-affinity linear variant of the endogenous agonist α-MSH” and shows directly how it binds MC4R and activates it. Afamelanotide is therefore an α-MSH analogue acting on several melanocortin receptors, not a selective molecule.
That does not mean it behaves exactly like Melanotan II — the sustained-release form produces a slow rise in concentration, which in clinical practice translates into a milder course. But the reasoning “no nausea because it does not touch MC4R” is wrong, and the claim that nausea only occurs at the start does not hold either: in the follow-up of 115 patients treated for up to eight years, nausea was the most frequently reported adverse event (Biolcati et al., 2015), and the Dutch cohort listed nausea, fatigue and headache as the typical self-limiting events (Wensink et al., 2020).
The disease it was tested in
Erythropoietic protoporphyria (EPP) is a rare inherited disorder of the haem biosynthesis pathway. Protoporphyrin IX — a light-sensitising substance — accumulates in the skin. On going out into the sun, patients feel first a burning pain, then redness and swelling. The pain is described as excruciating, and the disease restricts life drastically: before treatment, quality-of-life scores in the Italian-Swiss study stood at 31 ± 24 % of maximum (Biolcati et al., 2015). This background matters, because it explains what “efficacy” means in these trials: not a better tan, but the number of hours in the sun without pain.
Human data — two randomised trials
The authorisation rests on two multicentre, double-blind, placebo-controlled trials published together in the New England Journal of Medicine (Langendonk et al., 2015). The European trial enrolled 74 patients and the American one 94; they were randomly assigned 1:1 to an implant containing afamelanotide or to a placebo implant, inserted at two-month intervals. The primary endpoint was the number of hours of direct sun exposure without pain.
The results: in the US trial, after 6 months the median pain-free time was 69.4 hours in the treated group against 40.8 hours on placebo (P = 0.04). In the European trial, after 9 months the median was 6.0 hours against 0.8 hours (P = 0.005), and the number of phototoxic reactions was lower (77 against 146; P = 0.04). Quality of life improved in both trials. Adverse events were mostly mild, and serious ones were not attributed to the study drug.
One thing is easy to miss: the absolute figures differ more than tenfold between the two trials (69 hours against 6 hours) even though the drug was the same — a consequence of how exposure data were collected under each protocol. The sensible reading is the relative improvement over placebo within the same trial, not an hour count pulled out of context.
Human data — long-term observation
The Italian-Swiss follow-up covered 115 patients who received 1023 implants in total over a period of up to 8 years (Biolcati et al., 2015). Quality-of-life scores rose from 31 ± 24 % to 74 % of maximum and stayed at that level throughout the observation period. Only three people judged that the treatment had not met their expectations; 23 % stopped for other reasons, most often pregnancy or cost.
The Dutch cohort, run at the direction of the European Medicines Agency, covered 117 patients (Wensink et al., 2020). Treatment was continued by 115 of them, that is 98 %. Time spent outdoors rose by 6.1 hours per week (95 % CI 3.62–8.67; P < 0.001) and the mean quality-of-life score by 14.01 % (95 % CI 4.53–23.50; P < 0.001). Phototoxic reactions were less painful, but their number and duration did not change significantly — an honest distinction that marketing material usually omits.
The German registry, part of the European post-authorisation safety study, covered 200 patients (Homey et al., 2025). Quality of life rose significantly above baseline (P < 0.0001), 91 % of those who started continued treatment, and the safety profile in patients over 70 did not differ from the rest. A caveat: the study is run with the manufacturer's involvement and some authors have declared financial ties to it.
Nevi and dermatological monitoring
The commonest question about this peptide concerns moles: if it stimulates pigment cells, does it raise the risk of melanoma? This was tested directly in 15 EPP patients by assessing 103 acquired nevi under dermoscopy before treatment and at 5 and 12 months (Arisi et al., 2021). At 5 months every nevus of a given network type showed focal thickening of that network, and the number of so-called globules was higher — but by 12 months both changes had returned to baseline. Dermoscopic features suggestive of malignancy were never observed, and no new nevi developed. The authors conclude that the changes are reversible and do not indicate malignant transformation. This is a study of 15 people over 12 months, so it does not answer the question of risk after a decade; it answers only whether the observed “darkening” of moles is in itself a warning sign — it is not.
The regulatory history
The European Medicines Agency authorised Scenesse on 22 December 2014, for the prevention of phototoxicity in adult patients with erythropoietic protoporphyria (ema.europa.eu/en/medicines/human/EPAR/scenesse). Conditions came attached: a mandatory post-authorisation safety study and a European patient registry — which is where the cohorts described above come from. The US FDA approved the same product almost five years later, on 8 October 2019, under application NDA 210797 (accessdata.fda.gov — Drugs@FDA, NDA 210797). In both jurisdictions the indication is narrow and does not cover pigmentation in healthy people.
Safety and the limits of the evidence
The evidence base here is clearly better than for most compounds in this library — but it concerns one disease and one population. Everything known about long-term safety comes from EPP patients, in whom the benefit is large and the point of comparison is a life of excruciating pain after stepping into the sun. Carrying that profile over to a healthy person who wants to change their skin colour is an inference none of these studies supports.
Two gaps are concrete. First, the trials measured pain-free hours and quality of life, not protection against radiation damage to DNA or the longer-term risk of skin cancer — no study has tested this peptide as a substitute for sun protection. Second, the data on moles stop at 12 months and 15 patients. We deliberately give no methods of use and no doses; the figures above describe what was done in the clinical trials and are not a recommendation.
The wider context — the melanocortin family
Melanocortins are a family of peptides acting on five related receptors, from MC1R (pigment) to MC5R; different molecules hit different combinations of those switches and hence produce different outcomes. Melanotan II is a cyclic analogue that engages the central receptors more broadly, and bremelanotide (PT-141) is a derivative of it authorised for an entirely different indication. Afamelanotide is the case in this family that travelled the whole clinical path to the end — and it shows what separates a research peptide from a medicine.
Summary
Afamelanotide (Melanotan I, Scenesse) is a synthetic analogue of the hormone α-MSH dating from 1980, stimulating melanin production and the skin's defensive pathways through the MC1R receptor. Two randomised trials in the New England Journal of Medicine showed longer pain-free sun exposure in patients with erythropoietic protoporphyria, and registry observation covers 115 patients over a period of up to eight years plus several hundred more across Europe. The peptide is approved by the EMA (2014) and the FDA (2019) — for that one rare disease only. Two popular claims need correcting: afamelanotide is not selective for MC1R (it also activates MC4R, as the receptor structure showed), and nausea is not merely an initial problem — it is the most frequently reported adverse event in the multi-year follow-ups as well. Outside protoporphyria the data are preliminary: for pigmentation in healthy people, no study assessing long-term safety exists.
Sources
- Langendonk JG, Balwani M, Anderson KE, et al. Afamelanotide for Erythropoietic Protoporphyria. The New England Journal of Medicine. 2015;373(1):48–59. PMID: 26132941. DOI: 10.1056/NEJMoa1411481. pubmed.ncbi.nlm.nih.gov/26132941
- Wensink D, Wagenmakers MAEM, Barman-Aksözen J, et al. Association of Afamelanotide With Improved Outcomes in Patients With Erythropoietic Protoporphyria in Clinical Practice. JAMA Dermatology. 2020;156(5):570–575. PMID: 32186677. DOI: 10.1001/jamadermatol.2020.0352. pubmed.ncbi.nlm.nih.gov/32186677
- Biolcati G, Marchesini E, Sorge F, Barbieri L, Schneider-Yin X, Minder EI. Long-term observational study of afamelanotide in 115 patients with erythropoietic protoporphyria. British Journal of Dermatology. 2015;172(6):1601–1612. PMID: 25494545. DOI: 10.1111/bjd.13598. pubmed.ncbi.nlm.nih.gov/25494545
- Homey B, Schelonke K, Schlegel CM, et al. German Cohort Observational Study to Investigate the Short- and Long-Term Safety and Clinical Effectiveness of Afamelanotide 16 mg (SCENESSE) in Patients With Erythropoietic Protoporphyria (EPP). Photodermatology, Photoimmunology & Photomedicine. 2025;41(2):e13012. PMID: 40082741. DOI: 10.1111/phpp.13012. pubmed.ncbi.nlm.nih.gov/40082741
- Harms JH, Lautenschlager S, Minder CE, Minder EI. Mitigating photosensitivity of erythropoietic protoporphyria patients by an agonistic analog of alpha-melanocyte stimulating hormone. Photochemistry and Photobiology. 2009;85(6):1434–1439. PMID: 19656325. DOI: 10.1111/j.1751-1097.2009.00595.x. pubmed.ncbi.nlm.nih.gov/19656325
- Arisi M, Rossi M, Rovati C, et al. Clinical and dermoscopic changes of acquired melanocytic nevi of patients treated with afamelanotide. Photochemical & Photobiological Sciences. 2021;20(2):315–320. PMID: 33721252. DOI: 10.1007/s43630-021-00020-2. pubmed.ncbi.nlm.nih.gov/33721252
- Minder EI, Barman-Aksoezen J, Schneider-Yin X. Pharmacokinetics and Pharmacodynamics of Afamelanotide and its Clinical Use in Treating Dermatologic Disorders. Clinical Pharmacokinetics. 2017;56(8):815–823. PMID: 28063031. DOI: 10.1007/s40262-016-0501-5. pubmed.ncbi.nlm.nih.gov/28063031
- Heyder NA, Kleinau G, Speck D, et al. Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide. Cell Research. 2021;31(11):1176–1189. PMID: 34561620. DOI: 10.1038/s41422-021-00569-8. pubmed.ncbi.nlm.nih.gov/34561620
For in-vitro laboratory research only. It is not a human medicine and is not for treatment.