A practical reference on afamelanotide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-01-13. Anything still debated is marked as such rather than presented as settled.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
=== Processing of precursors === The precursors for systemin and AtPEP1 are both processed to yield one active peptide from the C-terminus of the precursor. It has been speculated that ProAtPEP1 is processed by CONSTITUTIVE DISEASE RESISTANCE 1, an apoplastic aspartic protease. The precursors to HypSys are processed into more than one active peptide. In tobacco, it is processed into two peptides, in petunia into three, and in sweet potato, possibly into six. At 291 amino acids long, the precursor to HypSys in sweet potato is the longest precursor described. The production of multiple signalling peptides from one precursor is a common feature found in animals.
Furthermore, the Japanese defensive plans had been directly obtained by the Allies from the wreckage of a plane carrying the commander-in-chief of the Imperial Japanese Navy's Combined Fleet, Admiral Mineichi Koga, in March 1944. During the course of the battle, American submarines torpedoed and sank two of the largest Japanese fleet carriers taking part in the battle. The American carriers launched a protracted strike, sinking one light carrier and damaging other ships, but most of the American aircraft returning to their carriers ran low on fuel as night fell. Eighty American planes were lost. Although at the time the battle appeared to be a missed opportunity to destroy the Japanese fleet, the Imperial Japanese Navy had lost the bulk of its carrier air strength and would never recover. This battle, along with the Battle of Leyte Gulf four months later, marked the end of Japanese aircraft carrier operations. The few surviving carriers remained mostly in port thereafter.
Ring A is then expanded via the polyketide synthase pathway to incorporate L-serine into ring B (figure 3). Ring A fragment is transferred from the peptidyl carrier protein (PCP) to the acyl carrier protein (ACP) by a keto-synthase (KS) domain, followed by transfer to malonyl-ACP via decarboxylative Claisen condensation catalysed by the enzyme pigJ. This fragment is then able to react with the masked carbanion formed from the pyridoxal phosphate (PLP) mediated decarboxylation of L-serine, which cyclizes in a dehydration reaction to yield the second pyrrole ring. This intermediate is then modified by oxidation of the primary alcohol to the aldehyde, catalysed by pigM, and methylation (which incorporates a methyl group from L-methionine onto the alcohol at the 6-position) catalysed by pigF and pigN. This yields the core A-B ring structure ready for further transformations, including to the tambjamines as well as the prodiginines.
=== Works cited === Adams, John, ed. (1805). The Annual Register, Or, A View of the History, Politics, and Literature for the Year ... J. Dodsley. Andrew, Christopher (2018). Secret World: A History of Intelligence. Yale University Press. ISBN 978-0-300-24052-8. Arnold, James R. (1995). Napoleon Conquers Austria: The 1809 Campaign for Vienna. Greenwood Publishing Group. ISBN 978-0-275-94694-4. Bell, David Avrom (2007). The First Total War: Napoleon's Europe and the Birth of Warfare as We Know it. Houghton Mifflin Harcourt. ISBN 978-0-618-34965-4. Black, Jeremy (2009). The War of 1812 in the Age of Napoleon. University of Oklahoma Press. ISBN 978-0-8061-4078-0. Briggs, Asa (1959). The Making of Modern England, 1783–1867: The Age of Improvement. Harper & Row. Bryant, Arthur (1944). Years of Victory, 1802–1812. Collins. Burke, Edmund (1808). The Annual Register, Or, A View of the History, Politics, and Literature for the Year ... J. Dodsley. Canales, Esteban (2004), 1808–1814: demografía y guerra en España (PDF) (in Spanish), Autonomous University of Barcelona, retrieved 3 May 2017 Chandler, David G. (1966). The Campaigns of Napoleon. Scribner. ISBN 978-0-02-523660-8. Clodfelter, Micheal (2017). Warfare and Armed Conflicts: A Statistical Encyclopedia of Casualty and Other Figures, 1492–2015 (4th ed.). McFarland. ISBN 978-1-4766-2585-0. Desan, Suzanne; Hunt, Lynn; Nelson, William Max (2013). The French Revolution in Global Perspective. Cornell University Press. ISBN 978-0-8014-6747-9. Dwyer, Philip (2013). Citizen Emperor: Napoleon in Power. Esdaile, Charles (2009).
== Inhibition == In vitro, glutathione reductase is inhibited by low concentrations of sodium arsenite and methylated arsenate metabolites, but in vivo, significant Glutathione Reductase inhibition by sodium arsenate has only been at 10 mg/kg/day. Glutathione reductase is also inhibited by some flavanoids, a class of pigments produced by plants.
Sources: en.wikipedia.org
Although orphan disease populations are the smallest, the cost of per-patient outlays among them are the largest and are expected to increase as more people with rare diseases become eligible for subsidies – in the U.S., for example, through the Affordable Care Act.
The simplest PK compartmental model is the one-compartmental PK model. This models an organism as one homogenous compartment. This monocompartmental model presupposes that blood plasma concentrations of the drug are the only information needed to determine the drug's concentration in other fluids and tissues. For example, the concentration in other areas may be approximately related by known, constant factors to the blood plasma concentration. In this one-compartment model, the most common model of elimination is first order kinetics, where the elimination of the drug is directly proportional to the drug's concentration in the organism. This is often called linear pharmacokinetics, as the change in concentration over time can be expressed as a linear differential equation
Refrigerated kimchi contains live LABs that continue to produce lactic acid, making the product sourer over time until it's too sour to be eaten. A LAB-based label contains similar LABs, food for the bacteria, and a pH-sensitive dye. As the LABs grow, they make more lactic acid and change the color. Phase change The melting of material can be used to produce an irreversible color change with heat. For example, a white wax is applied on top of a red piece of cardboard. When the wax melts off at a threshold temperature, the red becomes visible. Conversely, solidification can be used to make a freeze indicator, using the fact that some colloidal dispersions do not recover after freeze and thaw.
==== Spray-drying ==== As this method is traditionally used for small particles, it is used to produce tempeh powder for products such as soups, breads, tortillas, etc. However, this method can be expensive due to the bulky nature of the equipment.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.