If you have been reading about MC1R and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-01-11. Numbers and descriptions here follow the published literature rather than marketing material.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
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=== Pharmacogenomics === Genetic variations in cytochrome P450 enzymes can influence exposure to vortioxetine. CYP2D6 extensive metabolizers have approximately 2-fold higher clearance of vortioxetine than CYP2D6 poor metabolizers. The estimated clearance rates were 52.9, 34.1, 26.6, and 18.1 L/h for CYP2D6 ultra-rapid metabolizers, extensive metabolizers, intermediate metabolizers, and poor metabolizers. Area-under-the-curve levels of vortioxetine were 35.5% lower in CYP2D6 ultra-rapid metabolizers than in extensive metabolizers, though with significant overlap due to interindividual variability. Dosage adjustment for CYP2D6 ultra-rapid metabolizers is considered to not be necessary. Vortioxetine exposure in CYP2D6 poor metabolizers is expected to be approximately twice as high as in extensive metabolizers. Depending on the individual response, dosage adjustment may be considered for CYP2D6 poor metabolizers, with a maximum recommended dosage of 10 mg/day for known such individuals. In addition to CYP2D6, CYP2C19 extensive metabolizers have 1.4-fold higher clearance of vortioxetine than poor metabolizers. However, this is not considered to be clinically important and dose adjustment is not considered to be necessary based on CYP2C19 status.
=== Muscle spasticity === Tizanidine is approved and used as a muscle relaxant to treat muscle spasticity. It has been found to be as effective as other muscle relaxants and is more tolerable than baclofen and diazepam. Due to its short elimination half-life and duration, tizanidine is generally taken once every 6 to 8 hours as needed, with a maximum of 3 doses per 24 hours.
=== Names === Enobosarm is the generic name of the drug and its International Nonproprietary Name (INN). Ostarine was a tentative brand name of the drug created by GTx, Inc. that did not end up being used for marketing purposes but continues to be used as a synonym for the drug. Enobosarm is also known by the pharmaceutical developmental code names S-22 (synthesis paper), GTx-024 (GTx, Inc.), MK-2866 (Merck), and VERU-024 (Veru, Inc.).
Sources: en.wikipedia.org
=== Into Germany === After helping to secure the Ruhr, the 82nd Airborne Division took over Ludwigslust past the Elbe River, accepting the surrender of over 150,000 men of Lieutenant General Kurt von Tippelskirch's 21st Army on 2 May 1945. General Omar Bradley, commanding the US 12th Army Group, stated in a 1975 interview with Gavin that Field Marshal Sir Bernard Montgomery, commanding the Anglo-Canadian 21st Army Group, had told him that German opposition was too great to cross the Elbe. When Gavin's 82nd crossed the river, in company with the British 6th Airborne Division, the 82nd Airborne Division moved 36 miles in one day and captured over 100,000 troops, causing great laughter in Bradley's 12th Army Group headquarters.
=== Tag === The tag may be either a direct reporter, such as a fluorophore, or an affinity label such as biotin, or it may consist of a latent handle like an alkyne or azide for use with Huisgen 1,3-dipolar cycloaddition (also known as click chemistry). Reporter tags facilitate detection and isolation of labeled proteins. Common examples include fluorophores used for visualization via in-gel fluorescence and high-throughput gel-based screens, biotin for streptavidin-based enrichment followed by mass spectrometry, and isotopic labels for quantitative mass spectrometry. Alternatively, alkynes or azides can be incorporated as bio-orthogonal handles for post-labeling conjugation via click chemistry, enabling modular addition of fluorophores, affinity tags, or isotopic labels after proteome labeling. These "clickable" designs minimize steric hindrance at the active site and expand analytical flexibility, particularly for high-resolution liquid chromatography-mass spectrometry methods.
== Human spaceflight, space treaties, interplanetary probes (1961–1968) == The period from 1961 to 1968 began with the first men sent to space, the first robotic explorations of other planets; with missions to Venus and Mars conducted by both the Soviet Union and the United States, robotic landings on the Moon, and the gestation of US ambition to land a man on the Moon. The 1960s saw significant advancements in crewed spaceflight by both Cold War adversaries, as well as the first nuclear detonation in space, research into anti-satellite technology, and the signing of historic international outer space treaties.
Progesterone is a progestogen, or an agonist of the nuclear progesterone receptors (PRs), the PR-A, PR-B, and PR-C. In addition, progesterone is an agonist of the membrane progesterone receptors (mPRs), including the mPRα, mPRβ, mPRγ, mPRδ, and mPRϵ. Aside from the PRs and mPRs, progesterone is a potent antimineralocorticoid, or antagonist of the mineralocorticoid receptor, the biological target of the mineralocorticoid aldosterone. In addition to its activity as a steroid hormone, progesterone is a neurosteroid. Among other neurosteroid activities, and via its active metabolites allopregnanolone and pregnanolone, progesterone is a potent positive allosteric modulator of the GABAA receptor, the major signaling receptor of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). The PRs are expressed widely throughout the body, including in the uterus, cervix, vagina, fallopian tubes, breasts, fat, skin, pituitary gland, hypothalamus, and in other areas of the brain. In accordance, progesterone has numerous effects throughout the body. Among other effects, progesterone produces changes in the female reproductive system, the breasts, and the brain. Progesterone has functional antiestrogenic effects due to its progestogenic activity, including in the uterus, cervix, and vagina. The effects of progesterone may influence health in both positive and negative ways. In addition to the aforementioned effects, progesterone has antigonadotropic effects due to its progestogenic activity, and can inhibit ovulation and suppress gonadal sex hormone production.
==== Syria ==== In 2024 it was acknowledged that five SAS members were under investigation by the Defence Serious Crime Unit on suspicion of committing war crimes in Syria, though details were not disclosed by the Ministry of Defence.
Sources: en.wikipedia.org
=== United States === In the U.S., laboratory mice are not regulated under the Animal Welfare Act administered by the USDA APHIS. However, the Public Health Service Act (PHS) as administered by the National Institutes of Health does offer a standard for their care and use. Compliance with the PHS is required for a research project to receive federal funding. PHS policy is administered by the Office of Laboratory Animal Welfare. Many academic research institutes seek accreditation voluntarily, often through the Association for Assessment and Accreditation of Laboratory Animal Care, which maintains the standards of care found within The Guide for the Care and Use of Laboratory Animals and the PHS policy. This accreditation is, however, not a prerequisite for federal funding, unlike the actual compliance.
Biography at the Biographical Directory of the United States Congress Financial information (federal office) at the Federal Election Commission Legislation sponsored at the Library of Congress Profile at Vote Smart Campaign contributions at OpenSecrets.org Follow the Money – John Kennedy 2007 2005 2003 1999 Louisiana Treasurer campaign contributions
=== Adjunctive techniques === Additional procedures may be performed in conjunction with blepharoplasty to support eyelid position and optimize outcomes. These may include canthopexy or canthoplasty to stabilize the lateral eyelid, as well as midface elevation or fat repositioning to improve the transition between the lower eyelid and cheek.
=== Medications === Some medications are known to cause muscle atrophy, usually due to direct effect on muscles. This includes glucocorticoids causing glucocorticoid myopathy or medications toxic to muscle such as doxorubicin.
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.