PT-141 code is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-07-02. Numbers and descriptions here follow the published literature rather than marketing material.
Identity and purity are usually established with reversed-phase high-performance liquid chromatography combined with mass spectrometry. A gradient of water and acetonitrile containing trifluoroacetic acid is a common mobile phase, and ultraviolet detection near 214 nanometres responds to the peptide backbone. Mass spectrometry confirms the expected molecular mass and helps reveal truncation or oxidation products. Purity is reported as a peak-area percentage, a figure that depends on the wavelength and gradient used, so values from different laboratories are not always directly comparable. Peptide mapping and amino acid analysis provide additional confirmation when required.
Regulatory status varies by jurisdiction, where approved prescription products, compounded preparations and research-grade material are treated as distinct categories with different documentation requirements. Suppliers of research material commonly issue a certificate of analysis listing purity, identity and sometimes endotoxin content. Independent verification by a third-party laboratory is often recommended because self-reported figures are difficult to check. Literature discussions usually state the source, purity and storage conditions of the material used, since these details affect reproducibility. Analysts note that a reported purity figure does not by itself describe biological activity.
Lyophilised peptide is generally held below minus twenty degrees Celsius, protected from light and moisture, because hydrolysis and oxidation accumulate faster at ambient temperature. Once reconstituted, solutions are typically kept between two and eight degrees Celsius and used within a short window defined by the supplier. Repeated freeze-thaw cycles are avoided since they promote aggregation and loss of soluble material. Container material matters as well, because peptides adsorb to certain plastics and glass surfaces at low concentration. Stability figures supplied by a vendor apply only to the specific lot and buffer that were tested.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid before reconstitution |
| Solubility class | Soluble in water and aqueous buffers | Stock solutions often prepared in sterile water |
| Typical storage temperature | Minus twenty degrees Celsius or below | Dry powder, protected from light |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Ultraviolet detection near 214 nanometres |
| Common synonyms | PT-141 and bremelanotide | Code and generic name used interchangeably |
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.
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.
Published studies differ in design, population and endpoint definition, so results are not always directly comparable across reports. Some trials used patient-reported measures of desire and distress, while others tracked physiological or behavioural outcomes. Questions that remain open include the durability of effects beyond short follow-up periods, the frequency of transient blood pressure elevation observed after administration, and whether a subtype-selective analogue could separate central effects from pigmentation-related activity. These points are usually framed as unresolved rather than settled in review literature.
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.
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.
Whether the behavioral effect originates centrally, peripherally, or through both remains an active question. Animal experiments using receptor antagonists and site-specific injections point toward hypothalamic melanocortin circuits as a key locus, but translating those findings to humans is not straightforward. Blood pressure changes observed in trials suggest a vascular component that may be peripherally mediated. The relationship between receptor occupancy and reported effect has not been mapped in humans, and no validated biomarker predicts response. This gap makes it difficult to explain individual variability on pharmacological grounds alone.
Bremelanotide acts as an agonist at melanocortin receptors, a family of five G-protein-coupled receptors labeled MC1 through MC5. Binding studies indicate activity at several of these subtypes rather than strict selectivity for one. Signalling proceeds mainly through Gs-mediated activation of adenylyl cyclase, raising intracellular cyclic AMP. The MC4 receptor, expressed in hypothalamic and limbic circuits, is widely regarded as the subtype most relevant to sexual response. Because the molecule is not subtype-selective, effects at other melanocortin receptors are expected and are used to explain some observed side effects.
The peptide contains seven amino acids arranged in a ring, closed by a lactam bridge between a side-chain acid and an amine. This cyclic constraint holds the backbone in a defined conformation and increases resistance to enzymatic breakdown relative to linear analogs. N-terminal acetylation and a C-terminal amide further protect the molecule from exopeptidases. The result is a compound with a comparatively long circulation time for a small peptide. Structural modification of the bridge alters receptor affinity, which is one reason analogs in this family differ in their subtype preferences.
The declaration's first safeguard clause referred to protecting the civil and religious rights of non-Jews in Palestine. The clause had been drafted together with the second safeguard by Leo Amery in consultation with Lord Milner, with the intention to "go a reasonable distance to meeting the objectors, both Jewish and pro-Arab, without impairing the substance of the proposed declaration". Arabs constituted around 90% of the population of Palestine, but – as stated by Ronald Storrs, Britain's Military Governor of Jerusalem between 1917 and 1920 – they were "not so much [named but] lumped together under the negative and humiliating definition of 'Non-Jewish Communities'". Additionally, there was no reference to protecting the political rights of this group, as there was regarding Jews in other countries. This lack of interest was frequently contrasted against the commitment to the Jewish community, with various terms used over subsequent years to regard the two obligations as linked. A heated question was whether the status of both groups had "equal weight", which the British government and the Permanent Mandates Commission held to be the case in the 1930 Passfield white paper. Balfour stated in February 1919 that Palestine was considered an exceptional case in which, referring to the local population, "we deliberately and rightly decline to accept the principle of self-determination," although he considered that the policy provided self-determination to Jews. Avi Shlaim considers this the declaration's "greatest contradiction".
Traditional Chinese medicine also includes some human parts: the classic Materia medica (Bencao Gangmu) describes (also criticizes) the use of 35 human body parts and excreta in medicines, including bones, fingernail, hairs, dandruff, earwax, impurities on the teeth, feces, urine, sweat, organs, but most are no longer in use. Human placenta has been used an ingredient in certain traditional Chinese medicines, including using dried human placenta, known as "Ziheche", to treat infertility, impotence and other conditions. The consumption of the human placenta is a potential source of infection.
Richard Carthew et al. state in their 2004 study of siRNA/miRNA silencing pathways in Drosophila that siRNA-induced post-transcriptional gene silencing is initiated by the assembly of the RNA-induced silencing complex (RISC). RISC silences expression of certain genes by cleaving the mRNA molecules coding those genes. To begin the process in that system, they state that one of the two siRNA strands, the anti-sense guide strand, is loaded into the RISC while the other strand, the sense passenger strand, is degraded; they go on to state that certain Drosophila Dicer enzymes may be responsible for loading the guide strand into RISC. Then, in a perspective from 2009, the view is offered that "siRNA scans for and directs RISC" to a perfectly complementary sequence on the mRNA molecules. The cleavage of the mRNA molecules is thought to be catalyzed by the Piwi domain of Argonaute proteins of the RISC; the mRNA molecule is then cut precisely by cleaving the phosphodiester bond between the target nucleotides which are paired to siRNA residues 10 and 11, counting from the 5'end. As Orban and Izaurralde note with regard to a further study in Drosophila cells, "[f]ollowing this initial endonucleolytic cleavage, the mRNA is [further] degraded" by cellular exonucleases; they show that in this system, the 5' fragments "are rapidly degraded from their 3' ends by the exosomes, whereas the 3' fragments are degraded from their 5' ends by XRN1", a 5'-3' exoribonuclease.
Sources: en.wikipedia.org
On 17 September, at least 12 people were killed and more than 2,750 were wounded, including Hezbollah members and civilians, after the explosions of their pagers in Lebanon and Syria, including in Beirut. The attack resulted in 1,500 fighters being taken out of action, with many facing blindness or losing their hands. Among those injured was the Iranian ambassador, Mojtaba Amani. Several drones launched from Lebanon crossed the border. Hezbollah confirmed the death of 12 militants on that day. Also on 17 September, the Shin Bet claimed that it thwarted a Hezbollah attempt for assassinate a former senior defence official with a Claymore mine. On 18 September another series of explosions involving wireless devices was reported across Lebanon, killing at least 30 people and injuring 750 others. Hezbollah said that it carried out four strikes targeting IDF sites including in Neve Ziv and Beit Hillel with rockets and artillery. Lebanese media reported that Israeli strikes struck Al-Jbeen, Shama, Majdal Zoun, Kfar Kila, Kfar Shiuba, Houla, al-Taybeh, the forest in the vicinity of Kounine and Beit Yahoun, and the outskirts of Yater. The IDF said that it struck Hezbollah sites in Chihine, Tayibe, Blida, Meiss El Jabal, Aitaroun and Kfarkela and a Hezbollah weapons depot in Khiam in these airstrikes. On 19 September, the IDF said that it started carrying out airstrikes against Hezbollah to destroy its capabilities in southern Lebanon while heavy bombing was reported in Deir Qanoun En Nahr.
At the present time the Department promotes various scientific fields, running the whole gamut of base branches of classical physical chemistry: thermodynamics, kinetics, electrochemistry, catalysis, sorption processes. As the subjects of research, organic compounds unite all the aforesaid research areas. Over the last years staff members of the Department of Physical Chemistry made reports at conferences in many countries of the world: Canada, Poland, Republic of South Africa, Italy, Germany, Portugal, Czech Republic, USA, Ireland, Croatia, Spain, Sweden, Japan, Brazil. The head of the Department is Professor Boris N. Solomonov, Doctor of Science in Chemistry. The Department conducts research in the following fields:
"Tetraloop receptor motifs" are long-range tertiary interactions consisting of hydrogen bonding between the bases in the tetraloop to stemloop sequences in distal sections of the secondary RNA structure. In addition to hydrogen bonding, stacking interactions are an important component of these tertiary interactions. For example, in GNRA-tetraloop interactions, the second nucleotide of the tetraloop stacks directly on an A-platform motif (see above) within the receptor. The sequence of the tetraloop and its receptor often covary so that the same type of tertiary contact can be made with different isoforms of the tetraloop and its cognate receptor. For example, the self-splicing group I intron relies on tetraloop receptor motifs for its structure and function. Specifically, the three adenine residues of the canonical GAAA motif stack on top of the receptor helix and form multiple stabilizing hydrogen bonds with the receptor. The first adenine of the GAAA sequence forms a triple base-pair with the receptor AU bases. The second adenine is stabilized by hydrogen bonds with the same uridine, as well as via its 2'-OH with the receptor and via interactions with the guanine of the GAAA tetraloop. The third adenine forms a triple base pair.
A22, also known as S-(3,4-dichlorobenzyl) isothiourea, is a chemical compound with antibiotic activity. It is colorless, hygroscopic, and light-sensitive. A22 acts as a reversible inhibitor of the bacterial cell wall protein MreB, causing bacterial rod-shaped cells to form coccoid cells. The antibiotic activity of A22 has been studied primarily in Pseudomonas aeruginosa. However, A22 does not seem to be useful as an antibiotic in humans due to its cytotoxic and genotoxic effects on human peripheral blood mononuclear cells (PBMCs). Despite its cytotoxic effects in human cells, A22 has been used as a research tool to investigate the bacterial cytoskeleton. A22 binds directly to the actin homolog MreB in its nucleotide-binding pocket, blocking simultaneous ATP binding. As a consequence, A22 inhibits MreB polymerization and thus disrupts the cytoskeleton of bacteria, causing defects of morphology and chromosome segregation.
Sources: en.wikipedia.org
Purity is normally expressed as a percentage of total peak area from a chromatographic run. The value depends on the column, gradient and detection wavelength chosen. Results generated under different conditions are therefore not always interchangeable.
Cycling between frozen and thawed states promotes aggregation and can reduce the amount of soluble peptide. Adsorption to container walls also removes material from solution over time. Suppliers generally recommend aliquoting before freezing to limit the number of cycles.
A typical certificate lists lot number, appearance, purity by chromatographic area, identity confirmation and the analytical methods used. Some suppliers add endotoxin or residual solvent results. The document describes the tested lot only and does not extend to other batches.
PT-141 was the development code used for bremelanotide during its preclinical and early clinical programme. The peptide is now generally referred to by its international nonproprietary name.