If you have been reading about Cyclic heptapeptide 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.
Last reviewed on 2026-06-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
Across literature and commercial listings, the substance appears under several names, including bremelanotide, PT-141, and various brand designations. A CAS registry number provides a unique identifier for the compound, aiding retrieval from chemical databases. Synonym lists may also contain early development codes and descriptive chemical names. When consulting sources, researchers need to confirm that the cited names refer to the same molecular structure to avoid confusion. Naming consistency matters especially when comparing analytical data across publications.
PT-141 is a synthetic cyclic heptapeptide whose development code is bremelanotide. It belongs to the class of melanocortin receptor agonists and acts by mimicking endogenous peptide hormones. The compound originated from research on melanotan II, where investigators exploring derivatives found distinct pharmacological features. Unlike the parent compound, PT-141 showed effects on pathways related to sexual desire and function in early studies, prompting its development as a separate candidate. Its molecular design aimed to separate receptor activity from pigmentary effects.
The molecular backbone consists of seven amino acid residues joined into a ring through a disulfide bridge. This cyclic conformation is critical for receptor binding. The sequence includes an acetylated N-terminus and an amidated C-terminus, modifications that improve resistance to enzymatic breakdown. One residue is in the D-configuration, a feature that further stabilizes the peptide against protease activity. Together, the ring structure and specific stereochemistry determine selectivity among melanocortin receptor subtypes.
Approved use is narrow and jurisdiction-specific. In the United States, the injectable product is authorised for premenopausal women with acquired, generalised hypoactive sexual desire disorder, a diagnosis that requires documented distress. It is not approved for men, for postmenopausal women, or for use alongside hormonal contraceptives under the approved labelling. Outside regulated markets, the same peptide is frequently sold as a research chemical, where identity, purity, and sterility are not independently verified.
Bremelanotide is a synthetic cyclic heptapeptide developed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation and appetite signalling. Its structure contains seven amino acid residues joined by a lactam bridge that closes the ring between two side chains. The molecular formula is C50H68N14O10 and the nominal molecular mass is near 1025 daltons. Much of the early laboratory literature refers to the same molecule by the development code PT-141.
The compound emerged from a research programme examining melanocortin analogues for effects on skin pigmentation. During early human studies, participants reported spontaneous erections as an unexpected side effect, which redirected development toward sexual function rather than tanning. An intranasal formulation was investigated in clinical trials but did not reach market approval. A subcutaneous injectable version later completed the regulatory process, and the nasal route does not appear in approved labelling.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic peptide | Melanocortin receptor agonist family |
| Molecular weight | Approximately 1025 Da | Free base form |
| Appearance | White to off-white powder | Lyophilized product |
| Solubility | Soluble in water | Also dissolves in polar organic solvents |
| Storage temperature | -20 degrees Celsius | Dry and protected from light |
Activation of MC4R in the hypothalamus is thought to influence dopaminergic signaling, which in turn affects arousal and desire. This mechanism differs from that of phosphodiesterase type 5 inhibitors, which act primarily on vascular smooth muscle in the genital region. Because the pathway is central rather than peripheral, effects are not strictly dependent on local blood flow. The precise downstream cascade linking receptor binding to behavioral outcomes remains an area of ongoing investigation.
Clinical development of bremelanotide proceeded through several reformulation attempts. An early intranasal version was discontinued, and a subcutaneous auto-injector formulation later received approval for hypoactive sexual desire disorder in premenopausal women. Approval decisions have varied by country and over time, and the product has not been universally adopted. Blood pressure elevation is a documented effect, which is why some jurisdictions require monitoring after administration. The clinical evidence base continues to evolve as additional studies are published.
Bremelanotide is a cyclic heptapeptide that acts as an agonist at melanocortin receptors. It binds MC1R, MC3R, MC4R, and MC5R, with MC4R activation considered most relevant to sexual desire pathways in the central nervous system. The molecule is a synthetic analog of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation and energy regulation. Early research explored its use in tanning before attention shifted toward sexual dysfunction applications. Receptor binding affinity varies across these subtypes.
Identity and purity testing for this peptide typically relies on reversed-phase high-performance liquid chromatography with ultraviolet detection, reported as area-percent purity. Mass spectrometry, usually in tandem mode, confirms molecular mass and supports quantification in biological matrices. Sequence confirmation may use peptide mapping after enzymatic digestion, while nuclear magnetic resonance and circular dichroism supply supplementary structural detail. No single technique establishes identity alone, so laboratories compare retention time, mass, and fragment pattern against a verified reference standard.
The lactam ring that closes the peptide backbone improves resistance to exopeptidase attack, but the molecule stays susceptible to hydrolysis and oxidation once dissolved. Degradation accelerates with temperature, extreme pH, and light exposure, and repeated freeze-thaw cycles promote aggregation and material loss. Lyophilized powder held desiccated at or below minus twenty degrees Celsius is the common way to keep reference material. Reconstituted solutions are generally kept cold and used within a short window because their stability is far lower than that of the dry solid.
The melanocortin system comprises five G protein-coupled receptors, designated MC1 through MC5, that signal mainly through cyclic AMP accumulation. MC1R and MC2R are associated with pigmentation and adrenal steroid production, while MC3R and MC4R are expressed in the central nervous system and influence energy balance and behavior. MC5R appears in exocrine tissues. Natural agonists include alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone, and endogenous antagonists such as agouti-related protein modulate the same sites. This receptor family provides the framework within which bremelanotide activity is described.
Bremelanotide acts as an agonist at several melanocortin receptors, with the strongest reported activity at MC4R and measurable activity at MC1R and MC3R. Because MC4R is expressed in hypothalamic and limbic circuits, the proposed mechanism links receptor activation to modulation of central pathways involved in desire rather than to direct effects on peripheral genital tissue. The precise downstream steps remain incompletely characterized, and evidence for the involvement of specific neurotransmitters is suggestive rather than settled. Nausea and blood pressure elevation reported during trials are consistent with melanocortin signaling outside the intended target circuit.
Compared with melanotan II, bremelanotide is a smaller cyclic peptide with a more constrained backbone, which affects receptor selectivity and metabolic stability. Published descriptions give a plasma half-life on the order of a few hours after subcutaneous administration, with elimination through hepatic and renal routes and limited plasma protein binding. Central access is inferred from effects observed in animal models, although direct measurement in humans is limited. Handling and storage requirements follow from the peptide backbone, which is susceptible to hydrolysis and oxidation.
Routine characterisation of bremelanotide relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nm, where the peptide backbone absorbs. Mass spectrometry, typically in tandem mode with electrospray ionisation, confirms identity and supports quantification in biological matrices. Additional checks include amino acid analysis, peptide mapping after enzymatic digestion, and confirmation of the lactam bridge, since incomplete cyclisation produces a mass-shifted by-product. Purity values above 95 percent are common in reference-grade material, though reports vary in how strictly related substances are resolved from the parent peak.
The lyophilised solid is relatively stable when kept dry, protected from light and held at reduced temperature, commonly minus 20 degrees Celsius or lower for long-term storage. In solution the peptide is more vulnerable: tryptophan oxidation, hydrolysis of the lactam bridge and aggregation all become relevant over time, and the rate depends on pH, buffer composition and concentration. Repeated freeze-thaw cycles are generally avoided because they promote aggregation. Aqueous working solutions are typically prepared fresh or split into single-use aliquots to limit degradation before analysis.
==== Combination drugs ==== Butalbital/acetaminophen (Butapap) – combination of butalbital (GABAA receptor positive allosteric modulator and barbiturate) and acetaminophen (analgesic) Ergotamine/caffeine (Cafergot) – combination of ergotamine (non-selective monoamine receptor modulator and ergoline) and caffeine (adenosine receptor antagonist) Ergotamine/chlorcyclizine/caffeine (Anervan) – combination of ergotamine (non-selective monoamine receptor modulator and ergoline), chlorcyclizine (antihistamine and other actions), and caffeine (adenosine receptor antagonist) Meloxicam/rizatriptan (AXS-07; Symbravo) – combination of meloxicam (COX inhibitor/NSAID) and rizatriptan (triptan) [139] Naproxen sodium/sumatriptan (MT-400; SumaRT/Nap; Suvexx; Trexima; Treximet) – combination of naproxen (COX inhibitor/NSAID) and sumatriptan (triptan) – migraine [140] Paracetamol/codeine/buclizine (Migraleve Yellow) – combination of paracetamol (analgesic) and codeine (opioid) Paracetamol/codeine/buclizine (Migraleve Pink) – combination of paracetamol (analgesic), codeine (opioid), and buclizine (antihistamine and other actions) Paracetamol/dichloralphenazone/isometheptene (Amidrine) – combination of paracetamol (analgesic), dichloralphenazone (phenazone (COX inhibitor/NSAID) and chloral hydrate (GABAA receptor positive allosteric modulator)), and isometheptene (adrenergic receptor agonist) Paracetamol/metoclopramide (Paramax) – combination of paracetamol (analgesic) and metoclopramide (various actions) Sumatriptan/naproxen (Treximet) – combination of sumatriptan (triptan) and naproxen (COX inhibitor/NSAID)
=== Science and technology === Turin had an astronomical observatory used by Giovanni Plana. The scientist Amedeo Avogadro worked as a professor in Turin. Galileo Ferraris, a professor at Turin University, discovered the working principles of the electric motor during the 19th century. In modern times, Turin hosted the CSELT telco laboratory.
=== 15 December === President Zelenskyy stated that Russia should start to withdraw their troops by Christmas as a step to end the conflict. Russia responded that there would be "No Christmas Ceasefire" until Ukraine accepted its loss of territory. The Kyiv School of Economics published a report estimating that, as of November 2022, Russia's invasion had caused $136 billion in direct damage to Ukraine's infrastructure. Energy infrastructure, industry, public, and private enterprises were impacted the most. USAID delivered four excavators and over 130 generators to Kyiv for use in "boiler houses and heat supply stations" according to mayor Vitali Klitschko. The recently liberated city of Kherson was entirely without power following Russian shelling, which killed at least two people. The Kherson military administration stated that the city was hit 86 times with "artillery, MLRS, tanks, mortars and UAVs," in the past 24 hours. In the Donbas, Ukrainian forces bombarded Donetsk in the largest wave of shelling seen since 2014, according to mayor Alexey Kulemzin. Volker Türk, the United Nations High Commissioner for Human Rights, published a detailed summary of 441 killings including 8 girls during the conflict. The United States expanded its training to 500 Ukrainians each month at Germany.
The type of analyzer used to run the CBC affects the reference ranges as well. Reference ranges are therefore established by individual laboratories based on their own patient populations and equipment.
== Research needs == It can be difficult to apply research into OIH to average patients, because some research focused on people taking very high doses or in methadone rehabilitation programs. Opioid-induced hyperalgesia has also been criticized as overdiagnosed among chronic pain patients, due to poor differential practice in distinguishing it from the much more common phenomenon of opioid tolerance. The misdiagnosis of common opioid tolerance (OT) as opioid-induced hyperalgesia (OIH) can be problematic as the clinical actions suggested by each condition can be contrary to each other. Patients misdiagnosed with OIH may have their opioid dose mistakenly decreased (in the attempt to counter OIH) at times when it is actually appropriate for their dose to be increased or rotated (as a counter to opioid tolerance). a2 agonists, such as clonidine and dexmedetomidine, have been studied as alternatives or adjuncts to opioids for their analgesic properties in the perioperative setting. They have been shown to decrease the need for opioids after surgery, which may reduce the risk of hyperalgesic effects associated with prolonged opioid use. However, there is currently insufficient data to support the clinical effectiveness of a2 agonists in reducing postoperative OIH. Palmitoylethanolamide (PEA) has been studied for its anti-inflammatory and analgesic effects and emerging data suggests that it may have a role in delaying the onset of opioid tolerance and reducing the development of OIH when used in conjunction with opioids.
Sources: en.wikipedia.org
A commonly applied definition of tissue engineering, as stated by Langer and Vacanti, is "an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve Biological tissue function or a whole organ". In addition, Langer and Vacanti also state that there are three main types of tissue engineering: cells, tissue-inducing substances, and a cells + matrix approach (often referred to as a scaffold). Tissue engineering has also been defined as "understanding the principles of tissue growth, and applying this to produce functional replacement tissue for clinical use". A further description goes on to say that an "underlying supposition of tissue engineering is that the employment of natural biology of the system will allow for greater success in developing therapeutic strategies aimed at the replacement, repair, maintenance, or enhancement of tissue function". Developments in the multidisciplinary field of tissue engineering have yielded a novel set of tissue replacement parts and implementation strategies. Scientific advances in biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabricate or improve existing tissues in the laboratory from combinations of engineered extracellular matrices ("scaffolds"), cells, and biologically active molecules.
As with regular coffee, the green coffee bean itself is first roasted to bring out flavour and aroma. Using rotating cylinders ovens, the green beans are heated to 165 °C (329 °F) for between 8 and 15 minutes. The beans are then cooled and ground into 0.5-to-1.1-millimetre (0.020 to 0.043 in) pieces. The main byproduct of the instant coffee production process is spent coffee grounds; they can be used as biomass, for example to produce heat used in the manufacturing process. The mass of spent coffee grounds is about twice that of the soluble coffee produced.
By the end of the year, there were 12,000 Cuban soldiers inside Angola, nearly the size of the entire SADF presence in South West Africa. The FNLA suffered a crushing defeat at the Battle of Quifangondo when it attempted to take Luanda on 10 November, and the capital remained in FAPLA hands by independence.
negative supercoiling The supercoiling of a double-stranded DNA molecule in the direction opposite to the turn of the double helix itself (e.g. a left-handed coiling of a helix with a right-handed turn). Contrast positive supercoiling.
Sources: en.wikipedia.org
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.
It emerged from research on melanotan II. Investigators exploring derivatives observed distinct pharmacological features related to sexual function.
Common names include bremelanotide and PT-141. Chemical databases may also list early development codes and descriptive names.
It is a synthetic cyclic peptide that acts as an agonist at melanocortin receptors. It is not a hormone replacement therapy and not a vasodilator in the usual clinical sense, although it does affect vascular tone. Chemically it belongs to the melanocortin analogue family.