Everything below concerns RP-HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-21. Numbers and descriptions here follow the published literature rather than marketing material.
Bremelanotide is a synthetic cyclic heptapeptide developed under the research code PT-141. The code reflects its position in an internal compound series rather than a chemical classification, and the name bremelanotide was later adopted for regulatory filings. Structurally it belongs to the melanocortin peptide family and shares a core sequence motif with alpha-melanocyte-stimulating hormone. The compound is supplied as an acetate salt in aqueous solution for injection. In reference literature it is indexed under both the code and the generic name, a dual listing that can complicate database searches.
Early work on melanocortin analogs in the 1980s and 1990s produced peptides intended to influence pigmentation and appetite. One of these, melanotan II, was observed to affect sexual desire as an incidental finding in self-administration reports. Researchers then pursued analogs with altered receptor selectivity and improved handling characteristics, and PT-141 emerged from that program in the late 1990s. The development path moved from dermatology and metabolism toward a central nervous system application, a shift that shaped both trial designs and the eventual label.
Regulatory review of bremelanotide concluded in 2019 with approval in the United States for a defined indication in premenopausal women. The reviewed formulation is a single-use prefilled autoinjector given subcutaneously, and its label carries cardiovascular monitoring language tied to blood pressure changes recorded during trials. Availability outside the approving jurisdiction varies, and in several countries the compound remains unapproved or is handled as a prescription-only item. Compounded and research-grade material also circulates, and it differs from the reviewed product in purity, characterization, and chain of custody.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H68N14O10 | Cyclic heptapeptide core |
| Molecular weight | 1025.2 g/mol | Calculated for the free base |
| CAS registry number | 189691-06-3 | Free base; the acetate salt has a separate entry |
| Solubility class | Water-soluble | Freely soluble in aqueous media near neutral pH |
| Typical storage | 2 to 8 °C | Protect from light; avoid repeated freeze-thaw cycles |
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.
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.
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.
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.
==== Retrograde ejaculation ==== This means that the sperm is produced in the testes but on its way out, it gets misdirected into the bladder rather than coming out through the urethra. This can lead to a low volume of semen (hypospermia) or no semen production (aspermia). Structural or functional damage to the bladder neck muscle causes the backflow of semen during the ejaculation. Nerve damage caused by medical conditions such as diabetes or multiple sclerosis can affect the function of bladder neck muscle. Also, surgery or trauma along with the medications used for hypertension and benign prostatic hyperplasia can contribute to bladder neck problems. Retrograde ejaculation can be diagnosed by the presence of sperm in the urine.
=== Other conditions === Catatonia is also seen in many medical disorders, including encephalitis, meningitis, autoimmune disorders, focal neurological lesions (including strokes), alcohol withdrawal, abrupt or overly rapid benzodiazepine withdrawal, cerebrovascular disease, neoplasms, head injury, and some metabolic conditions (e.g.,homocystinuria, diabetic ketoacidosis, hepatic encephalopathy, and hypercalcaemia).
Doillon started acting at age five, starring in Kung Fu Master directed by Agnès Varda. She has since worked with directors including Jean Pierre Améris, Jacques Doillon, Guillaume Canet, Abel Ferrara and Maïwenn.
Sources: en.wikipedia.org
===== Extraterrestrial origin of homochirality ===== Some analyses of organic molecules in extraterrestrial materials, such as carbonaceous chondrite meteorites and asteroids, identified small enantiomeric enrichments in a few L-amino acids and D-sugars, leading to the proposition that initial enantiomeric bias could have been seeded on Earth from space. That the enantiomeric biases measured in meteorites and astroids were consistent with that found in biology added credence to this idea, and experimental work showed plausible mechanisms for creating this enantiomeric bias in extraterrestrial materials. It was hypothesized that circularly polarized light originating from Mie scattering on aligned interstellar dust particles may trigger the formation of an enantiomeric excess within chiral material in space. Interstellar and near-stellar magnetic fields can align dust particles in this fashion. Another speculation (the Vester-Ulbricht hypothesis) suggests that fundamental chirality of physical processes such as that of the beta decay (see Parity violation) leads to slightly different half-lives of biologically relevant molecules. The amino acids in asteroids Bennu and Ryugu show no chiral bias. The Murchinson meteorite contained only racemic amino acids.
== Precautions == An equianalgesic chart can be a useful tool, but the user must take care to correct for all relevant variables such as route of administration, cross tolerance, half-life and the bioavailability of a drug. For example, the narcotic levorphanol is 4–8 times stronger than morphine, but also has a much longer half-life. Simply switching the patient from 40 mg of morphine to 10 mg of levorphanol would be dangerous due to dose accumulation, and hence frequency of administration should also be taken into account. There are other concerns about equianalgesic charts. Many charts derive their data from studies conducted on opioid-naive patients. Patients with chronic (rather than acute) pain may respond to analgesia differently. Repeated administration of a medication is also different from single dosing, as many drugs have active metabolites that can build up in the body. Patient variables such as sex, age, and organ function may also influence the effect of the drug on the system. These variables are rarely included in equianalgesic charts.
Efficacy was evaluated in KEYNOTE-590 (NCT03189719), a multicenter, randomized, placebo-controlled trial that enrolled 749 participants with metastatic or locally advanced esophageal or gastroesophageal junction carcinoma who were not candidates for surgical resection or definitive chemoradiation. In May 2021, the US FDA approved pembrolizumab in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy for the first-line treatment of people with locally advanced unresectable or metastatic HER2 positive gastric or gastroesophageal junction (GEJ) adenocarcinoma. Approval was based on the prespecified interim analysis of the first 264 participants of the ongoing KEYNOTE-811 (NCT03615326) trial, a multicenter, randomized, double‑blind, placebo‑controlled trial in participants with HER2‑positive advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma who had not previously received systemic therapy for metastatic disease. In July 2021, the US FDA approved pembrolizumab for high-risk, early-stage, triple-negative breast cancer in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery. The FDA also granted regular approval to pembrolizumab in combination with chemotherapy for people with locally recurrent unresectable or metastatic triple-negative breast cancer whose tumors express PD-L1 (Combined Positive Score [CPS] ≥ 10) as determined by an FDA-approved test.
Sources: en.wikipedia.org
PT-141 was the internal development code assigned to bremelanotide during preclinical research. Reference sources sometimes index the peptide under the code rather than the generic name. The two terms describe the same molecule.
They are related but distinct cyclic peptides. Melanotan II is an earlier and less selective melanocortin analog. Bremelanotide was developed later with a narrower receptor profile and a defined clinical application.
The reviewed product is given by subcutaneous injection using a single-use autoinjector. Administration occurs under prescription supervision. The device delivers one fixed amount per use rather than a measured or adjustable quantity.
The peptide is polar and charged, and reversed-phase chromatography with acidic mobile phases resolves it well from related substances. Ultraviolet detection near 214 nm gives adequate sensitivity without derivatisation.