This is a working overview of Melanotan II, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-25 and is reviewed periodically as new material appears.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
=== Absorption and distribution === As calciseptine is injected by the snake into its prey along with the rest of its venom, it does not have to pass the protective barrier of the skin and is injected directly into the tissues and/or bloodstream of the prey. No research has been conducted on the toxicokinetics of calciseptine specifically, but general research about snake toxin dynamics is available. Although the toxic peptides are generally small (about 60 amino acids), their size is sufficient to prevent them from crossing epithelial layers like the blood–brain barrier. Bioavailability measurements have been conducted for several snake venoms. For example, cobra venom has been found to have a bioavailability of 41.7% when injected intramuscular, and for other venoms this may even be less than 10%. These values are quite low compared to those of most therapeutic drugs, which usually have a bioavailability of nearly 100% after intramuscular injection. In general, toxic peptides of 10-40 amino acids have been found to have a relatively poor bioavailability due to their size and hydrophilicity. Thus, calciseptine, containing 60 amino acids, is expected to have a low bioavailability as well.
=== Epimerization === Radical SAM epimerases are responsible for the regioselective introduction of D-amino acids into RiPPs. Two well-known enzymes have been thoroughly described in RiPP biosynthetic pathways. Radical SAM peptide epimerases use a critical cysteine residue to provide back an H-atom to the epimerized residue in addition to unique features for RiPP interaction. Two well-known enzymes have been thoroughly described in RiPP biosynthetic pathways.
== Operation == The extraction cells consist of hollow bodies with inlets and outlets of liquid connection. The cells are first filled with the liquid chosen to be the stationary phase. Under rotation, the pumping of the mobile phase is started, which enters the cells from the inlet. When entering the flow of mobiles phase forms small droplets according to the Stokes' law, which is called atomization. These droplets fall through the stationary phase, creating a high interface area, which is called the extraction. At the end of the cells, these droplets unite due to the surface tension, which is called settling. When a sample mixture is injected as a plug into the flow of mobile phase the compounds of the mixtures elute according to their partition coefficients:
Sources: en.wikipedia.org
=== Cell cycle regulation === Although preferentially cytosolic, SIRT2 transiently shuttles to the nucleus during the G2/M transition of the cell cycle, where it has a strong preference for histone H4 lysine 16 (H4K16ac), thereby regulating chromosomal condensation during mitosis. During the cell cycle, SIRT2 associates with several mitotic structures including the centrosome, mitotic spindle, and midbody, presumably to ensure normal cell division. Finally, cells with SIRT2 overexpression exhibit marked prolongation of the cell cycle.
== History == 1996 - Institut für Bioanalytik GmbH was founded by Herbert Stadler, IBA introduces Strep-tag products 1998 - Acquisition of NAPS Göttingen GmbH (Nucleic Acid Products Supply) 1999 - Biologics joint venture with GBF Braunschweig 2001 - Institut für Bioanalytik GmbH was renamed to IBA GmbH 2003 - IBA introduces Streptamer cell isolation technology 2004 - Operations segmented into Protein, Gene and Cell TAGnology business units 2007 - IBA introduces StarGate cloning system 2008 - Innovation Award for StarGate 2010 - IBA introduces Fab-Streptamer technology 2011 - Innovation Award for Streptamer cell isolation technology 2012 - IBA introduces Fab-TACS (Formerly known as T-CATCH) column based cell purification 2014 - IBA earned its ISO 9001:2008 certification for Quality Management Standard, IBA introduces Strep-Tactin XT products 2015 - 6th foreign Trade Award of Lower Saxony (Germany), IBA launches MEXi mammalian expression system 2016 - IBA introduces cell selection device FABian
The convergent orientation of the catalytic triad in the active site of serine and cysteine proteases independently in over 20 enzyme superfamilies. The use of an N-terminal threonine for proteolysis. The existence of distinct families of carbonic anhydrase is believed to illustrate convergent evolution. The use of (Z)-7-dodecen-1-yl acetate as a sex pheromone by the Asian elephant (Elephas maximus) and by more than 100 species of Lepidoptera. The biosynthesis of plant hormones such as gibberellin and abscisic acid by different biochemical pathways in plants and fungi. The protein prestin that drives the cochlea amplifier and confers high auditory sensitivity in mammals, shows numerous convergent amino acid replacements in bats and dolphins, both of which have independently evolved high frequency hearing for echolocation. This same signature of convergence has also been found in other genes expressed in the mammalian cochlea The repeated independent evolution of nylonase in two different strains of Flavobacterium and one strain of Pseudomonas. The myoglobin from the abalone Sulculus diversicolor has a different structure from normal myoglobin but serves a similar function — binding oxygen reversibly. "The molecular weight of Sulculus myoglobin is 41kD, 2.5 times larger than other myoglobins." Moreover, its amino acid sequence has no homology with other invertebrate myoglobins or with hemoglobins, but is 35% homologous with human indoleamine dioxygenase (IDO), a vertebrate tryptophan-degrading enzyme. It does not share similar function with IDO.
Sources: en.wikipedia.org
Substantial cephalopelvic disproportion Unfavorable fetal position or presentation (e.g., transverse lies) undeliverable without conversion before delivery Obstetric emergencies where maternal or fetal risk-to-benefit ratio favors surgery Fetal distress when delivery is not imminent Umbilical cord prolapse Uterine activity fails to progress adequately Hyperactive or hypertonic uterus Vaginal delivery is contraindicated (e.g., invasive cervical carcinoma, active genital herpes infection, total placenta previa, vasa previa, cord presentation or prolapse) Uterine or cervical scarring from previous cesarean section or major cervical or uterine (e.g., transfundal) surgery Unengaged fetal head History of hypersensitivity to oxytocin or any ingredient in the formulation
in situ (of a scientific experiment or biological process) Occurring or made to occur in a natural, uncontrolled setting, or in the natural or original position or place, as opposed to in a foreign cell or tissue type or in an artificial environment.
A great number of software tools for protein structure prediction exist. Approaches include homology modeling, protein threading, ab initio methods, secondary structure prediction, and transmembrane helix and signal peptide prediction. In particular, deep learning based on long short-term memory has been used for this purpose since 2007, when it was successfully applied to protein homology detection and to predict subcellular localization of proteins. Some recent successful methods based on the CASP experiments include I-TASSER, HHpred and AlphaFold. In 2021, AlphaFold was reported to perform best. Knowing the structure of a protein often allows functional prediction as well. For instance, collagen is folded into a long-extended fiber-like chain and it makes it a fibrous protein. Recently, several techniques have been developed to predict protein folding and thus protein structure, for example, Itasser, and AlphaFold.
Biotechnology is a multidisciplinary field that involves the integration of natural sciences and engineering sciences to achieve the application of organisms and parts thereof for products and services. The term biotechnology was first used by Károly Ereky in 1919 to refer to the production of products from raw materials with the aid of living organisms. The core principle of biotechnology involves harnessing biological systems and organisms, such as bacteria, yeast, and plants, to perform specific tasks or produce valuable substances. Biotechnology has a significant impact on many areas of society, from medicine to agriculture to environmental science. One of the key techniques used in biotechnology is genetic engineering, which allows scientists to modify the genetic makeup of organisms to achieve desired outcomes. This can involve inserting genes from one organism into another, and consequently, creating new traits or modifying existing ones through gene editing. Other important techniques used in biotechnology include tissue culture, which allows researchers to grow cells and tissues in the lab for research and medical purposes, and fermentation, which is used to produce a wide range of products such as beer, wine, and cheese. The applications of biotechnology are diverse and have led to the development of products like drugs, biofuels, genetically modified crops, and innovative materials. It has also been used to address environmental challenges, such as developing biodegradable plastics and using microorganisms to clean up contaminated sites.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.