Melanotan-1 vs Melanotan-2: How the Two Melanocortin Peptides Differ in Research
Melanotan-1 vs Melanotan-2 compared: melanocortin receptor selectivity, afamelanotide context and what separates the two peptides in research.
Important notice: This article is intended solely for scientific information and research purposes. Melanotan-2 is a research peptide, not intended for human consumption and not approved as a medicine or cosmetic. Afamelanotide (Melanotan-1, brand name Scenesse) is a prescription-only medicine that we do not sell. Nothing here is dosing advice or a treatment recommendation.
TL;DR: two names, two different molecules
Different backbones. Melanotan-1 (afamelanotide) is a 13-amino-acid linear peptide. Melanotan-2 is a truncated, cyclic 7-residue lactam. They are not "versions" of each other. Different receptor profiles. Afamelanotide is functionally MC1R-selective at its approved clinical exposure. MT-2 is non-selective and also engages MC3R, MC4R and MC5R, which is why it produces effects afamelanotide does not. Different regulatory status. Afamelanotide (Scenesse) is EMA- and FDA-approved for a rare-disease indication, delivered as a physician-administered implant. MT-2 is not approved anywhere and faces tightening restriction in some jurisdictions. Different safety signatures. MT-2's non-selective activity plus uncontrolled bolus dosing in unsupervised use is mechanistically linked to nausea, spontaneous erections, priapism case reports and melanocytic (mole) changes that afamelanotide's pivotal trials did not show. We sell MT-2 as a research peptide only. Not afamelanotide, not a tanning product, no human-use claims.
Why these two names get confused
Melanotan-1 and Melanotan-2 both descend from the same starting point: alpha-melanocyte-stimulating hormone (alpha-MSH), the natural signaling peptide that activates the melanocortin receptor family (MC1R through MC5R) to control skin pigmentation, energy balance and aspects of sexual function. Both were engineered in the 1980s-90s peptide chemistry programs that tried to make alpha-MSH more stable and more potent. From there, the two molecules went in different directions, ended up with different structures, different receptor behavior, and eventually different regulatory fates. One became an approved orphan drug for a rare skin disease. The other stayed an unapproved research chemical that keeps showing up in case reports and regulatory warnings.
The shared "Melanotan" name is a historical accident of nomenclature, not a sign that the two peptides are interchangeable. This article lays out where they actually diverge: structure, receptor pharmacology, approval status, and the safety literature, so the difference is clear rather than assumed.
Structure: a linear tridecapeptide versus a cyclic core
Melanotan-1 / afamelanotide keeps the full 13-residue alpha-MSH backbone with two modifications for stability and potency: norleucine at position 4 (Nle4, resists oxidation) and a D-phenylalanine at position 7 (D-Phe7, resists enzymatic breakdown). The sequence is Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2, molecular weight about 1,646.8 g/mol.
Melanotan-2 is a different design altogether: a truncated, cyclic lactam. It drops the N-terminal Ser-Tyr-Ser and C-terminal Gly-Pro-Val of alpha-MSH, keeping only the core His-D-Phe-Arg-Trp pharmacophore, then closes it into a macrocycle with a lactam bridge between an aspartate and a lysine residue, capped with an N-terminal norleucine: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, molecular weight approximately 1,024 Da. The cyclization is what gives MT-2 its high potency and protease resistance relative to a comparably sized linear fragment. The two peptides are not structurally unrelated: beyond the shared His-D-Phe-Arg-Trp core, both carry an N-terminal acetyl cap, a C-terminal amide, a norleucine substitution, and a lysine residue, features that reflect a common engineering lineage even though the overall backbone geometry (linear versus cyclic) differs.
In short: same starting material, two different engineering solutions. One preserved the full peptide and refined it. The other stripped it down and locked it into a ring.
Half-life is a formulation story, not just a chemistry story
Given as a simple subcutaneous injection, Melanotan-I shows a biexponential plasma profile: an absorption-phase half-life of 0.07 to 0.79 hours and a terminal half-life of 0.8 to 1.7 hours (PMID 9113347). Melanotan-2's free-peptide half-life has been reported at roughly 30 to 40 minutes in early pharmacology characterization, a figure that should be read as approximate rather than a precisely sourced number. What makes the approved afamelanotide product, Scenesse, behave so differently in the clinic (apparent half-life around 15 hours, median time to peak plasma concentration around 36 hours, effect sustained for about 60 days) is the biodegradable controlled-release implant it is delivered in, not a change in the peptide's intrinsic clearance. Melanotan-2 has no equivalent approved depot formulation; research and unsupervised use is bolus injection with peptide-level, not implant-level, pharmacokinetics.
Receptor pharmacology: selective versus non-selective
This is the mechanistic center of the comparison, and it explains almost everything else in this article.
Both peptides act on the melanocortin receptor family, but they do not act on the same receptors to the same degree:
- Afamelanotide (MT-1) is functionally MC1R-selective at the exposure produced by its approved implant. MC1R is the receptor on epidermal melanocytes responsible for eumelanin synthesis, the pigmentation pathway. At the low, sustained systemic exposure the implant delivers, central melanocortin receptors (MC3R, MC4R) are engaged only marginally, which is consistent with the narrow, predictable side-effect profile seen in its pivotal trials.
- Melanotan-2 is non-selective. It activates MC1R (pigmentation, the same pathway afamelanotide uses), but it also activates MC3R and MC4R, hypothalamic receptors that govern appetite, energy balance and sexual arousal/erectile function, and MC5R. This broader receptor engagement is the direct reason MT-2 produces effects that afamelanotide's approved dosing avoids or produces only at background, near-placebo levels: spontaneous erections and increased libido (MC4R-mediated), dose-dependent and sometimes severe nausea plus appetite suppression (MC3R/MC4R, area postrema), and a stretching-and-yawning behavioral complex documented in melanocortin pharmacology.
The first human pharmacology study of MT-2, a small pilot in three healthy men dosed subcutaneously at 0.01 to 0.03 mg/kg once daily on weekdays for two weeks, already captured this dual character: two of three subjects showed increased pigmentation by one week, and the paper also recorded mild nausea at most dose levels, grade II somnolence and fatigue in one subject, and a stretching-yawning complex with spontaneous penile erections lasting one to five hours post-injection (PMID 8637402). That combination, pigmentation plus central arousal and nausea effects in the same small cohort, is the pharmacological fingerprint of a non-selective melanocortin agonist, and it is not something afamelanotide's clinical trials reproduced.
Approval status: one orphan drug, one unapproved research chemical
Afamelanotide (Scenesse), Clinuvel Pharmaceuticals, is an approved medicine. The European Medicines Agency granted conditional marketing authorization under exceptional circumstances on 22 December 2014, for prevention of phototoxicity in adults with confirmed erythropoietic protoporphyria (EPP), a rare genetic disorder that causes severe, painful skin reactions to light. The FDA approved Scenesse on 8 October 2019 for the same indication, following Priority Review and Orphan Drug designation, the first FDA-approved treatment shown to increase pain-free light exposure in EPP patients. It is delivered as a 16 mg subcutaneous implant, administered by a physician every 60 days, timed to the spring-through-autumn sun-exposure season. It carries no approval, in the EU, US or elsewhere, for cosmetic tanning, appetite modulation or sexual function. Those would be off-label uses of a prescription drug we do not sell.
Melanotan-2 is not approved anywhere as a medicine or a cosmetic, by the FDA, the EMA or any other major regulator. It remains, everywhere, a research chemical without a validated human dosing protocol. If anything, the regulatory trend is tightening. Australia's Therapeutic Goods Administration reclassified Melanotan-2 to Schedule 9 (prohibited substance), effective February 2026. In May 2025, UK Trading Standards issued a public warning against nasal "tanning spray" products containing MT-2, on two grounds at once: the products are marketed as cosmetics to sidestep medicines law, and independent testing commissioned by the BBC (University of Sunderland) found MT-2 content inconsistent or unclear in the majority of sampled products, meaning buyers of these sprays frequently do not even know what dose, or what substance, they are actually receiving.
What we actually sell, stated plainly
We sell Melanotan-2 exclusively as a research peptide: for laboratory and preclinical research use, never for human consumption, never as a tanning product. We do not sell afamelanotide or Scenesse, which is a prescription-only medicine administered by physicians for a specific rare-disease indication.
Safety literature: why the two profiles look so different
The clinical trial record for afamelanotide is comparatively narrow and predictable. In the two pooled phase 3, multicenter, randomized, double-blind, placebo-controlled trials that supported approval (PMID 26132941), the EU arm enrolled 74 adults with EPP (38 afamelanotide, 36 placebo) receiving five implants over nine months; median pain-free sunlight exposure was 6.0 hours with afamelanotide versus 0.8 hours with placebo (P = 0.005), and phototoxic reactions numbered 77 versus 146 (P = 0.04). The US arm enrolled 94 patients (48/45) over three implants across six months, with pain-free exposure of 69.4 versus 40.8 hours (P = 0.04). Adverse events were headache (34-40% versus 29-39% placebo), nausea (18-19% versus 17-18% placebo, barely above placebo), nasopharyngitis (12-21%), and mild implant-site hyperpigmentation in roughly a third of afamelanotide recipients. No drug-related serious adverse events were identified.
Melanotan-2's literature, drawn mostly from small pharmacology studies and case reports rather than large controlled trials, tells a different story, one that lines up with its broader receptor engagement and its typical bolus (non-depot) dosing pattern in unsupervised settings:
- Nausea is common and can be dose-dependent. In one crossover study of ten men with organic erectile dysfunction receiving 0.025 mg/kg subcutaneous MT-2, severe nausea occurred after 4 of 19 active injections (PMID 11018622). A second crossover study in twenty men found severe nausea in roughly 12.9% of subjects at the same dose (PMID 11035391).
- Spontaneous erections and, in overdose, priapism are a reproducible signal, mechanistically tied to MC4R. In the ten-man crossover study, erections occurred after 12 of 19 active injections versus 1 of 21 placebo injections, with mean tip rigidity above 80% sustained for 45.3 minutes versus 1.9 minutes on placebo (P = 0.047, PMID 11018622). In the twenty-man study, erection without sexual stimulation occurred in 17 of 20 men, and increased sexual desire was reported after 13 of 19 (68%) MT-2 doses versus 4 of 21 (19%) placebo doses (P less than 0.01, PMID 11035391). At the extreme end, this same MC4R activity has produced priapism as a urological emergency in case reports: one following an MT-2 overdose (PMID 23537392), another following cosmetic self-injection, both requiring emergency intervention (PMID 30796078).
- Overdose has produced systemic toxicity. A case report describes a 39-year-old man who self-injected a single 6 mg MT-2 dose, roughly six times a typical starting dose, and developed acute sympathomimetic signs (body aches, sweating, anxiety, blood pressure 151/85 mmHg, heart rate 130-146 bpm, dilated pupils, tremor), rhabdomyolysis (peak creatine kinase 17,773 IU/L), acute kidney injury (creatinine 2.25 mg/dL) and elevated troponin, managed over roughly three days in intensive care (PMID 23121206).
- Melanocytic (mole) changes are a genuine dermatological monitoring concern. A case report describes eruptive new nevi and darkening of pre-existing nevi within 24 hours of a single MT-2 injection (PMID 24334249). Two independent case reports describe melanoma temporally associated with MT-2 use: one melanoma (PMID 21564053) and one melanoma in situ (PMID 22724573). This matters clinically because darkening or new moles are exactly the warning signs used to screen for melanoma, so pigment changes triggered by a melanocortin agonist can complicate that surveillance.
One 2026 case report needs careful reading, not overstatement
A February 2026 case report (PMID 41752902) describes a 42-year-old man who developed oral mucosal pigmentation, a melanosis, not a melanoma, after roughly nine weeks of subcutaneous MT-2 injections, which partially regressed after he stopped. The authors explicitly state that causality is not established and name several confounders: pre-existing gum pigmentation, smoking, and tanning-bed use. It is a different and much less severe finding than the two separate melanoma case reports above, and the two should not be conflated. A separate, additional risk layer applies specifically to the unregulated cosmetic-spray market discussed above: UK Trading Standards testing found MT-2 detectable in only 6 of the 10 sampled nasal spray products, at inconsistent strength, with the rest of unclear composition. That product-quality problem sits alongside, not in place of, the pharmacological harms documented above (priapism, rhabdomyolysis, melanocytic changes), which follow from MT-2's own receptor activity and are not resolved by product purity.
For anyone working with MT-2 in a research context, awareness of mole changes as a monitoring point is a reasonable, evidence-based takeaway from this literature, distinct from any dosing recommendation. Our earlier article, Melanotan-2 in Summer 2026: What the New Case Reports and Regulatory Warnings Really Say, goes deeper into the case-report and regulatory-warning detail.
Tanning peptide that activates melanin production in the skin. Stimulates melanocyte receptors for natural UV-free pigmentation. Also researched for appetite regulation and libido effects.
USP-grade sterile water with 0.9% benzyl alcohol (near-neutral, ~pH 6) - the standard solvent for reconstituting lyophilized peptides. Essential accessory for any peptide research. Each vial is sealed and ready to use.
Sterile 1 mL graduated laboratory syringe with a 31G x 6 mm fine tip. Individually wrapped, latex-free, pyrogen-free, PVC-free, with a high-contrast 0.01 mL black scale for precise liquid measuring and transfer.
Common misconceptions, corrected
"Melanotan-1 and Melanotan-2 are the same peptide, just numbered differently." They are not. Different backbones (13-residue linear versus 7-residue cyclic core), different receptor selectivity, different approval status, and materially different reported side-effect profiles. They share a research lineage in alpha-MSH analog development, not an identity.
"Since afamelanotide is approved, Melanotan-2 must be close to approval too." No. Afamelanotide is approved only for EPP photoprotection, via a physician-administered implant. MT-2 has no approval anywhere, and the regulatory direction (Australia's 2026 Schedule 9 reclassification) is toward more restriction, not less.
"Selling Melanotan-2 is basically selling a version of the approved tanning drug." This gets the mechanism and the product both wrong. We do not sell afamelanotide or Scenesse. MT-2's broader receptor activity (appetite, erectile effects) and its case-report safety signature (priapism, dose-dependent severe nausea, melanocytic changes) are not what afamelanotide's pivotal trials showed. They are two different molecules with two different regulatory and safety records.
"Both Melanotans are approved tanning drugs." Neither is approved for tanning. Afamelanotide's approval is narrowly for EPP light-tolerance, a rare-disease photoprotection indication; pigmentation is a mechanism underlying that approved use, not a labeled cosmetic indication.
"MT-2's nausea and flushing are minor, and every melanocortin peptide causes them, including afamelanotide." The placebo-controlled afamelanotide trials found nausea only marginally above placebo (18-19% versus 17-18%). MT-2 studies report dose-dependent, sometimes severe nausea (up to roughly 13% severe at study doses), precisely because MT-2 engages MC3R/MC4R pathways that afamelanotide's approved dosing largely spares.
Frequently asked questions
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This article is for scientific and research information only. Melanotan-2 is not approved as a medicine or cosmetic and is not intended for human consumption; afamelanotide (Melanotan-1, Scenesse) is a prescription-only medicine that we do not sell. Nothing in this article is medical, dosing, or treatment advice.
Research context for English-speaking buyers
Most of our English-speaking customers ship to the UK, Ireland, Malta or other English-as-second-language EU territories. The regulatory picture differs per country.
- Relevant authorities
- MHRA (UK, post-Brexit), HPRA (Ireland, EU-aligned), FDA Section 503A bulks list (US, restricted Cat 2 status of several peptides as of 2026)
- Customs and VAT
- EU shipments include 19% VAT; UK shipments after Brexit are now extra-EU and may attract UK VAT plus a handling fee at import
- Typical shipping window
- EU 2-4 working days, UK 4-7 working days, other international 7-14 working days, depending on customs
Research-grade peptides shipped from our EU warehouse are sold for laboratory use only and are not authorised for human or veterinary therapeutic application in any of the destination jurisdictions. US customers should be aware that the FDA Section 503A bulks list classification (and the April 2026 reclassification of twelve compounds) only governs compounding pharmacies, not direct-to-researcher imports for non-clinical work. UK buyers should declare the consignment on import and may be asked for a research justification by HMRC. We provide a CoA per batch identified by colour code rather than serial number; customs sometimes asks for this document when clearing the parcel.