Everything below concerns cyclic heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
From a pharmacokinetic standpoint, the peptide is usually delivered by injection because oral bioavailability is very low; proteases in the digestive tract degrade it rapidly. After subcutaneous administration, plasma concentrations reach a peak within roughly one hour. Its elimination half-life is relatively short, with most reports placing it in the range of a few hours. Nasal formulations have also been examined, though absorption varies widely between individuals. Metabolism proceeds mainly through peptidase cleavage, and the resulting products are excreted by the kidneys.
PT-141 initiates cellular signaling by binding to specific subtypes within the melanocortin receptor family. These receptors belong to the G protein-coupled receptor superfamily, and activation raises intracellular cyclic adenosine monophosphate levels. This cascade ultimately influences neuronal circuits in the central nervous system that are associated with sexual desire and arousal. Research indicates the compound's action concentrates in hypothalamic regions rather than peripheral tissues, which helps explain some observed pharmacological features. The selectivity of receptor binding underlies its functional differences.
| 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 |
Reconstitution is usually performed with sterile water or a dilute acetic acid solution, and the choice of solvent affects both dissolution speed and final pH. Complete dissolution should be confirmed by visual inspection before any aliquot is taken, since undissolved particles can concentrate in the sampling volume. Repeated freeze-thaw cycles are the most common cause of gradual loss of purity, so dividing a stock into single-use aliquots at the first opportunity is standard practice. Working solutions kept refrigerated are generally used within days rather than weeks.
Identity and purity are established with orthogonal methods rather than a single test. Reverse-phase high-performance liquid chromatography with ultraviolet detection gives a purity figure by area normalization, while mass spectrometry confirms the expected molecular ion. Amino acid analysis or peptide mapping can detect sequence errors that a mass value alone would miss, and residual counterion content is sometimes measured separately. Common impurities include truncated sequences, oxidized residues, and deamidated products; reporting them individually is more informative than a single composite purity number.
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.
Early clinical work used an intranasal formulation, and later programmes switched to subcutaneous delivery for more consistent absorption. A subcutaneous product received regulatory approval in the United States in 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder. Approval followed phase 3 trials in which active treatment separated from placebo on desire and distress measures, though the average difference was modest. Labeling carries a caution about transient blood pressure elevation, so cardiovascular history is assessed before prescribing. Questions about durability of benefit beyond several months remain open.
Published discussion sits at the intersection of peptide chemistry, neuroendocrinology and sexual medicine. Trial reports emphasise change scores on validated instruments, while mechanistic papers focus on hypothalamic circuits and receptor selectivity. Because placebo response in this field is large, effect sizes are usually reported with confidence intervals rather than as isolated averages. Reviews note that female and male data sets are not interchangeable and should be read separately. Diagnostic terminology has been revised over time, which complicates comparison between older and newer studies.
Bremelanotide is a synthetic cyclic heptapeptide that acts on a family of G-protein-coupled receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide associated with pigmentation and several central signalling pathways. A lactam bridge constrains the ring and slows enzymatic breakdown, which distinguishes it from the linear parent molecule. Research interest moved over time from pigment biology toward central nervous system effects, particularly circuits connected to sexual desire. Parenteral delivery is used because oral bioavailability is poor.
=== The analyte is adsorbed onto the electrode surface === Adsorbed species give simple voltammetric responses: ideally, at slow scan rates, there is no peak separation, the peak width is 90mV for a one-electron redox couple, and the peak current and peak area are proportional to scan rate (observing that the peak current is proportional to scan rate proves that the redox species that gives the peak is actually immobilised). The effect of increasing the scan rate can be used to measure the rate of interfacial electron transfer and/or the rates of reactions that are coupltransfer. This technique has been useful to study redox proteins, some of which readily adsorb on various electrode materials, but the theory for biological and non-biological redox molecules is the same (see the page about protein film voltammetry).
=== Early Exploration and late-18th Century Politics === By the early 1700s, traders from South Carolina were visiting the Overhill towns regularly, and following the discovery of Cumberland Gap in 1748, long hunters from Virginia began pouring into the Tennessee Valley. At the outbreak of the French and Indian War in 1754, the Cherokee supported the British, who in return constructed Fort Loudoun in 1756 to protect the Overhill towns from the French and their allies. During the Anglo-Cherokee War, however, the Cherokee attacked the fort and killed its occupants in 1760. A peace expedition to the Overhill towns led by Henry Timberlake passed along the river through what is now Knoxville in December 1761. The Cherokee supported the British during the Revolutionary War, and after the end of the war, North Carolina, which considered the Tennessee Valley part of its territory, deemed Cherokee claims to the region void. North Carolina made plans to cede its Trans-Appalachian territory to the federal government, but decided to open up the lands to settlement first. In 1783, land speculator William Blount and his brother, John Gray Blount, convinced North Carolina to pass a law offering lands in the Tennessee Valley for sale. Later that year, an expedition consisting of James White (1747–1820), James Connor, Robert Love, and Francis Alexander Ramsey, explored the Upper Tennessee Valley, and discovered the future site of Knoxville. Taking advantage of Blount's land-grab act, White took out a claim for the site shortly afterward.
== In popular culture == The television medical dramas Heartland (2007) and Three Rivers (2009) were largely based on UPMC and the University of Pittsburgh's Thomas E. Starzl Transplantation Institute. In both cases the hospitals are fictionalized, but in the latter series UPMC is also specifically referred to as another Pittsburgh-area hospital.
The introduction or modification of a protecting group occasionally influences the reactivity of the whole molecule. For example, diagrammed below is an excerpt of the synthesis of an analogue of Mitomycin C by Danishefsky.
Opium was widely used for food, medicine, ritual, and as a painkiller throughout ancient civilizations including Greece, Egypt, and Islamic societies up to medieval times. The production methods have not significantly changed since ancient times. Through selective breeding of the Papaver somniferum plant, the content of the phenanthrene alkaloids morphine, codeine, and to a lesser extent thebaine has been greatly increased. In modern times, much of the thebaine, which often serves as the raw material for the synthesis for oxycodone, hydrocodone, hydromorphone, and other semisynthetic opiates, originates from extracting Papaver orientale or Papaver bracteatum. In preparation for the Second World War, the U.S. Army contracted farmers in the State of Sinaloa, Mexico, to grow opium crops. This was to provide morphine (the gold standard of analgesia) for injured soldiers. Modern opium production, once widely prohibited, still involves large-scale cultivation—especially in Afghanistan—where it is harvested by scoring poppy pods to collect latex used for both illicit drugs and legal medicines, with recent Taliban-led reductions cutting cultivation in Afghanistan by over 95%. For the illegal drug trade, the morphine is extracted from the opium latex, reducing the bulk weight by 88%. It is then converted into heroin which is almost twice as potent.
Sources: en.wikipedia.org
=== Alternative routes of administration === In rhesus macaques, BCG shows "unprecedented" rates of TB protection when given intravenously. Some risks must be evaluated before it can be translated to humans. The University of Oxford Jenner Institute is conducting a study comparing the efficacy of injected versus inhaled BCG vaccine in already-vaccinated adults.
=== Privacy and independence === A Nature editorial suggests medical care could become dependent on AI models that could be taken down at any time, are difficult to evaluate, and may threaten patient privacy. Its authors propose that health-care institutions, academic researchers, clinicians, patients and technology companies worldwide should collaborate to build open-source models for health care of which the underlying code and base models are easily accessible and can be fine-tuned freely with own data sets.
== L == Lactobacillus Lactobacillus acidophilus Lactobacillus bulgaricus Lactobacillus casei Lactococcus lactis Legionella pneumophila Leptospira Leptospira interrogans Leptospira noguchii Listeria monocytogenes
== Clinical studies == PF-04455242 reached phase 1 clinical trials for bipolar depression prior to the discontinuation of its development in 2010. Its development was discontinued upon unfavorable toxicological findings in animals that had been exposed to the drug for 3 months. Along with JDTic, which was also discontinued due to toxicity findings early in clinical trials, PF-04455242 was one of the first KOR antagonists to be developed for potential treatment of psychiatric disorders. It was in phase 1 trials by 2009 and was first described in the scientific literature by 2010.
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 primarily activates specific subtypes in the melanocortin receptor family. These receptors are G protein-coupled and mediate signaling mainly within the central nervous system.