A practical reference on Cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-15. Anything still debated is marked as such rather than presented as settled.
Development began with intranasal formulations investigated for erectile dysfunction, but blood pressure elevation limited that route and prompted a switch to subcutaneous delivery. Clinical testing then shifted toward hypoactive sexual desire disorder in premenopausal women, and a subcutaneous product received United States approval in 2019. Later trials examined other populations with mixed results, and questions about effect size, durability and patient selection remain open in the peer-reviewed literature. Research interest continues in parallel with the broader melanocortin field, where several synthetic analogues are studied together.
PT-141 is the research code for bremelanotide, a cyclic heptapeptide derived from alpha-melanocyte-stimulating hormone. The molecule belongs to the melanocortin receptor agonist family and shows highest affinity for the MC4 receptor subtype, with weaker activity at MC1, MC3 and MC5. Its structure retains the core His-Phe-Arg-Trp sequence that defines melanocortin recognition, while cyclization and terminal modifications improve metabolic stability relative to the parent hormone. Early work classified the compound as a centrally acting agent rather than a peripherally acting vasodilator, which shaped subsequent development priorities.
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.
| Property | Value | Notes |
|---|---|---|
| Research code | PT-141 | Used in early literature before the generic name became common |
| Generic name | Bremelanotide | International nonproprietary name |
| Peptide class | Cyclic heptapeptide | Seven residues joined by a lactam bridge |
| Primary receptor | MC4R | Lower affinity reported at MC1R, MC3R and MC5R |
| Route studied clinically | Subcutaneous injection | Intranasal route was abandoned after pressor effects |
Bremelanotide is a cyclic heptapeptide that binds several melanocortin receptors rather than one. In vitro assays report agonist activity at MC1R, MC3R, MC4R and MC5R, with MC4R generally treated as the subtype most relevant to sexual effects. MC4R is expressed in hypothalamic nuclei involved in appetite, energy balance and motivated behaviour, which provides a plausible route for central action. Selective MC4R agonists studied in animals produce comparable behavioural changes, supporting that interpretation.
How receptor activation translates into a change in desire is not established in detail. Proposed steps include modulation of dopaminergic signalling in reward circuits and downstream effects on autonomic tone. Human data consist mainly of clinical trials measuring self-reported outcomes rather than direct measurements of brain activity or transmitter release. The transient rise in blood pressure sometimes observed after administration is likewise reported consistently but explained only partly by known melanocortin pathways.
Melanocortin receptors form a family of five G-protein-coupled proteins, labelled MC1R through MC5R, that respond to peptides derived from pro-opiomelanocortin. Alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone are the best-known endogenous ligands. The receptors are distributed differently across tissues, so a single agonist can produce effects in the brain, skin, adrenal gland and vasculature. This distribution explains why one peptide can influence both pigmentation and motivated behaviour.
Clinical research typically uses randomised, double-blind, placebo-controlled designs. The most common primary endpoint is the desire domain score of the Female Sexual Function Index, sometimes paired with a distress measure. Secondary outcomes include arousal, satisfaction, and event-based counts of satisfying sexual episodes. Across trials, average improvements are modest and individual responses vary widely. Whether benefits persist beyond a few months, and whether they depend on baseline hormone status, remain open questions rather than settled findings.
Melanocortin receptors form a family of five G-protein-coupled receptors designated MC1 through MC5. Bremelanotide binds most strongly at MC4R and MC1R, with weaker activity reported at MC3R and MC5R. MC4R is expressed in hypothalamic nuclei that coordinate energy balance and aspects of sexual behaviour. The prevailing interpretation is that central MC4R activation, rather than peripheral vascular effects alone, drives the reported changes in desire. This account remains partly inferential, since direct receptor-level measurement in living humans is not practical.
Handling procedures emphasize minimizing moisture uptake, since the dried solid is hygroscopic and can draw water when warmed to room temperature before a vial is opened. Laboratories record lot number, purity, counter-ion content, and residual solvent data supplied by the producer. Impurity profiles are compared run to run, and any shift in retention time or peak shape prompts re-verification against a reference standard. Certificates of analysis are treated as claims to be checked rather than accepted at face value.
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.
Early research on PT-141 grew out of work on melanotan II, a related cyclic peptide studied for pigmentation. Investigators observed that centrally acting melanocortin agonists also influenced sexual behaviour in animal models, and the programme shifted toward that endpoint. A nasal formulation was evaluated in clinical trials but showed inconsistent absorption, and later studies used subcutaneous administration instead. Regulatory approval in the United States followed in 2019 for a defined population of premenopausal women with acquired, generalised hypoactive sexual desire disorder. That approval was specific to that group rather than a broad indication.
Bremelanotide acts as a non-selective agonist at melanocortin receptors, with reported activity at MC1R, MC3R, MC4R and MC5R. The proposed basis for its central effects is activation of MC4R populations in the hypothalamus, a region associated with appetite and reproductive signalling. Because the peptide carries a net positive charge and polar side chains, it does not cross biological membranes freely, which is one reason oral administration is not the standard route. Effects generally appear within an hour of parenteral administration and are described as centrally mediated rather than peripheral.
Bremelanotide, developed under the code PT-141, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone. Its structure is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, with a lactam bridge joining the aspartate and lysine side chains. The molecule has the formula C50H68N14O10 and a monoisotopic mass near 1025 daltons. It is commonly prepared as the acetate salt and appears as a white to off-white lyophilised powder in solid form. The free acid is the pharmacologically relevant species, while the counter-ion improves handling and dissolution.
Relatively low during the preovulatory phase of the menstrual cycle, progesterone levels rise after ovulation and are elevated during the luteal phase, as shown in the diagram. Progesterone levels tend to be less than 2 ng/mL prior to ovulation and greater than 5 ng/mL after ovulation. If pregnancy occurs, human chorionic gonadotropin is released, maintaining the corpus luteum and allowing it to maintain levels of progesterone. Between seven and nine weeks gestation, the placenta begins to produce progesterone in place of the corpus luteum in a process called the luteal-placental shift. After the luteal-placental shift, progesterone levels start to rise further and may reach 100 to 200 ng/mL at term. Whether a decrease in progesterone levels is critical for the initiation of labor has been argued and may be species-specific. After delivery of the placenta and during lactation, progesterone levels are very low. Progesterone levels are low in children and postmenopausal people. Adult males have levels similar to those in women during the follicular phase of the menstrual cycle.
A PEGylated lipid is used as an excipient in both the Moderna vaccine and the Pfizer–BioNTech COVID-19 vaccine. Both RNA vaccines consist of Messenger RNA, or mRNA, encased in a bubble of oily molecules called lipids. Proprietary lipid technology is used for each. In both vaccines, the bubbles are coated with a stabilizing molecule of polyethylene glycol. As of December 2020, there is some concern that PEG could trigger an allergic reaction, as appears to have occurred by 19 December, in at least three "Alaska health care worker" people who were administered the Pfizer–BioNTech COVID-19 vaccine. The particular PEGylated molecule in the Moderna vaccine is known as DMG-PEG 2000. Pegvaliase (Biomarin) – PEGylated recombinant phenylalanine ammonia-lyase for the treatment of Phenylketonuria, approved by the FDA for the US in May 2018. Adynovate – PEGylated Antihemophilic Factor VIII for the treatment of patients with hemophilia A. (Baxalta, 2015) Irinotecan liposome (Onivyde) – PEGylated liposomal irinotecan hydrochloride trihydrate for the treatment of metastatic pancreatic cancer in adults proceeding treatment with gemcitabine-based therapy. (Ipsen, 2015) Plegridy – PEGylated Interferon Beta-1a for the treatment of patients with relapsing forms of multiple sclerosis. (Biogen, 2014) Naloxegol (Movantik) – PEGylated naloxol for the treatment of opioid-induced constipation in adults patients with chronic non-cancer pain (un-pegylated methadone can cause adverse gastrointestinal reactions).
where Vatom = Vcell/n and n is the number of atoms per unit cell of volume Vcell. The unit cell of silicon has a cubic packing arrangement of 8 atoms, and the unit cell volume may be measured by determining a single unit cell parameter, the length a of one of the sides of the cube. The CODATA value of a for silicon is 5.431020511(89)×10−10 m. In practice, X-ray crystallography measurements are carried out on a distance known as d220(Si), which is the distance between the planes denoted by the Miller indices {220}, and is equal to a/√8. The isotope proportional composition of the sample used must be measured and taken into account. Silicon occurs in three stable isotopes (28Si, 29Si, 30Si), and the natural variation in their proportions is greater than other uncertainties in the measurements. The atomic weight Ar for the sample crystal can be calculated, as the standard atomic weights of the three nuclides are known with great accuracy. This, together with the measured density ρ of the sample, allows the molar volume Vm to be determined:
Methylestradiol, or 17α-methylestradiol (17α-ME), also known as 17α-methylestra-1,3,5(10)-triene-3,17β-diol, is a synthetic estrane steroid and a derivative of estradiol. It is specifically the derivative of estradiol with a methyl group at the C17α positions. Closely related steroids include ethinylestradiol (17α-ethynylestradiol) and ethylestradiol (17α-ethylestradiol). The C3 cyclopentyl ether of methylestradiol has been studied and shows greater oral potency than methylestradiol in animals, similarly to quinestrol (ethinylestradiol 3-cyclopentyl ether) and quinestradol (estriol 3-cyclopentyl ether).
== History == The disorder was first described in 1959 by psychiatrist and researcher Albert Stunkard as "night eating syndrome" (NES). The term "binge eating" was coined to describe the same bingeing-type eating behavior but without the exclusive nocturnal component. There is less research on BED than there is on anorexia or bulimia.
Sources: en.wikipedia.org
Silanization is the attachment of an organosilyl group to some chemical species. Almost always, silanization is the conversion of a silanol-terminated surface to an alkylsiloxy-terminated surface. This conversion confers hydrophobicity to a previously hydrophilic surface. This process is often used to modify the surface properties of glass, silicon, alumina, quartz, and metal oxide substrates, which all have an abundance of hydroxyl groups. Silanization differs from silylation, which usually refers to attachment of organosilicon groups to molecular substrates.
== Research == In the early 21st century, extensive research is occurring in the field of nanoparticle drug delivery systems to the brain. One of the common diseases being studied in neuroscience is Alzheimer's disease. Many studies have been done to show how nanoparticles can be used as a platform to deliver therapeutic drugs to these patients with the disease. A few Alzheimer's drugs that have been studied especially are rivastigmine, tacrine, quinoline, piperine, and curcumin. PBCA, chitosan, and PLGA nanoparticles were used as delivery systems for these drugs. Overall, the results from each drug injection with these nanoparticles showed remarkable improvements in the effects of the drug relative to non-nanoparticle delivery systems. This possibly suggests that nanoparticles could provide a promising solution to how these drugs could cross the BBB. One factor that still must be considered and accounted for is nanoparticle accumulation in the body. With long-term and frequent injections that are often required to treat chronic diseases such as Alzheimer's disease, polymeric nanoparticles could potentially build up in the body, causing undesirable effects. This area for concern would have to be further assessed to analyze these possible effects and to improve them.
== External links == Association of Biomolecular Resource Facilities ABRF Federation of American Societies for Experimental Biology FASEB ABRF Discussion Forum Journal of Biomolecular Techniques ABRF at LinkedIn Leadership
==== COVID-19 ==== Epidemiological research has shown that the COVID-19 pandemic accelerated the opioid crisis. The overarching trend of opioid overdose data has shown a plateau in deaths around 2017–18, with a sudden and acute rise in 2019 primarily attributed to synthetic opioids like fentanyl. In 2020, there were 93,400 drug overdoses in the U.S. with >73% (approximately 69,000) due to opioid overdose. One JAMA review by Gomes et al. showed that estimated years of life loss (YLL) due to opioid toxicity in the U.S. increased by 276%. This increase was particularly felt by those ages 15 to 19, whose YLL increased nearly threefold. Younger male adults had the largest effect size. Other reviews of U.S. and Canadian opioid data coinciding with the onset of COVID-19 suggested significant increases in opioid-related emergency medicine utilization, increased positivity for opioids, and surprisingly no to decreased change in naloxone dispensation. Telehealth played a large role in OUD treatment access, and legislation on telehealth continues to evolve. A study of Medicare beneficiaries with new-onset OUD showed that those who received telehealth services had a 33% lower risk of death by overdose. Minority groups such as Black and Hispanic Americans have also been shown to benefit from the increased access due to telehealth programs introduced during the pandemic, despite increasing disparity gaps in other OUD-related outcomes. The DEA and HHS have extended telemedicine flexibility for prescribing controlled substances such as buprenorphine for OUD through 31 December 2024.\\
Sources: en.wikipedia.org
The first patch for the Xbox 360 version was released about two weeks after release to fix some of the game stability issues players had reported. The patch was found to introduce more problems to the game for some users, including occasional freezes, bad framerates, and audio-related issues, though methods to resolve these issues through the console's cache system were outlined by Irrational Games. In December 2007, a common patch was released for both the Xbox 360 and Windows version. The patch included additional content such as new Plasmids, new achievements for the Xbox 360 version, and a FOV lock that allowed widescreen players a wider field of view without losing vertical information. The patch also added in an option to disable the use of Vita-Chambers, a feature requested by players to make the game more challenging, as well as an achievement to complete the game at its hardest setting without using a Vita-Chamber. In 2014, 2K Games released a DRM-free version of BioShock in the Humble 2K Bundle, followed by DRM-free releases on GOG in 2018.
== Drug-drug interactions == As of 2004 it was known that oxandrolone greatly increases warfarin's blood-thinning effect, sometimes dangerously so. In April 2004, Savient Pharmaceuticals published a safety alert through the FDA warning healthcare professionals of this. Oxandrolone also inhibits the metabolism of oral hypoglycemic agents. It may worsen edema when taken alongside corticosteroids or adrenocorticotropic hormone.
== StAR-independent steroidogenesis == While loss of functional StAR in the human and the mouse catastrophically reduces steroid production, it does not eliminate all of it, indicating the existence of StAR-independent pathways for steroid generation. Aside from the human placenta, these pathways are considered minor for endocrine production. It is unclear what factors catalyze StAR-independent steroidogenesis. Candidates include oxysterols which can be freely converted to steroid and the ubiquitous MLN64.
== List of major publications in English == Vladimir Kh. Khavinson. Peptides and Ageing. // Neuroendocrinology Letters. — Vol. 23, Suppl. 3, Special Issue. — 2002. — 144 p. Khavinson, Malinin. Gerontological Aspects of Genome Peptide Regulation. // Basel (Switzerland): Karger AG. — 2005. — 104 p. Khavinson. Peptidergic regulation of ageing. // SPb.: Humanistica. — 2009. — 48 p. Khavinson, Morozov, Anisimov. Experimental Studies of the Pineal Gland Preparation Epithalamin. // The Pineal Gland and Cancer. — Bartsch C., Bartsch H., Blask D.E., Cardinali D.P., Hrushesky W.J.M., Mecke D. (Eds.) — Springer-Verlag, Berlin, Heidelberg. — 2001. — P. 294–306. Vladimir N. Anisimov, Vladimir Kh. Khavinson. Small Peptide-associated Modulation of Aging and Longevity. // Modulating Aging and Longevity. — Kluwer Academic Publishers (Printed in the United Kingdom) — Suresh I.S. Rattan (ed.). — 2003. — P. 279–301. Vladimir N. Anisimov, Vladimir Kh. Khavinson. Pineal Peptides as Modulators of Aging. // Aging Interventions and Therapies. — World Scientific. — Suresh I.S. Rattan (ed.). — 2005. — P. 127–146. Khavinson, Mikhailova. Health and Aging in Russia. // Global Health and Global Aging. / (ed. by Mary Robinson et al.); foreword by Robert Butler. — 1st ed. — 2007. — P. 226–237. Khavinson, Neroev, Trofimova, Osokina. Unique method for restoration of retinal functions in case of different diseases. // SPb. — 2011. — 32 p.
== Effects of Algicidal Bacteria on Algae == Algicidal bacteria can cause harm to algae in multiple different ways. Depending on the type of algae and type of bacteria, the mechanisms and resulting effects can vary.
Sources: en.wikipedia.org
The code designates bremelanotide, a cyclic heptapeptide melanocortin receptor agonist. It served as an internal research identifier before the compound entered formal clinical development. The code and the generic name refer to the same molecule.
MC4R is generally described as the principal target, based on binding affinity and functional assays. Activity at MC1R, MC3R and MC5R is reported as weaker. Receptor selectivity is one reason the compound was pursued for central rather than vascular effects.
Both are synthetic melanocortin analogues built on a similar cyclic peptide scaffold. Bremelanotide is described in the literature as a metabolite-derived analogue of melanotan II rather than the same substance. The two differ in terminal modifications, which affect half-life and receptor profile.
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.