How to Reconstitute PT-141 (Bremelanotide)

What PT-141 (Bremelanotide) Is

PT-141, formally known as Bremelanotide, is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (α-MSH). It is classified as a melanocortin receptor agonist, with research interest centered on its activity at the melanocortin-4 receptor (MC4R) and, to a lesser extent, the melanocortin-1 receptor (MC1R). The compound is supplied as a lyophilized powder for laboratory research and is not intended for human or veterinary use. Bremelanotide is also known by the research codes PT-141 and by the developmental designation Palatin Technologies PT-141. Its molecular formula is C50H68N14O10, and its molecular weight is approximately 1025.2 g/mol. The peptide sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, with the cyclic structure formed by a lactam bridge between the side chains of Asp and Lys. The N-terminus is acetylated and the C-terminus is a free acid. These identifiers are provided for laboratory identification and analytical characterization only.

The pharmacological work on Bremelanotide centers on the melanocortin receptor family, a group of G-protein-coupled receptors that signal primarily through the cyclic AMP pathway. MC4R is expressed in the central nervous system and is the receptor subtype most frequently implicated in the behavioral and neuroendocrine effects observed in animal models of melanocortin agonist administration.

Research Studies

Bremelanotide and Subcutaneous Administration in Premenopausal Women with HSDD

Two Phase 3, randomized, double-blind, placebo-controlled, parallel-group trials with optional open-label extensions evaluated the efficacy of bremelanotide administered subcutaneously on an as-needed basis for the treatment of hypoactive sexual desire disorder (HSDD), with or without decreased arousal, in premenopausal females [1][2]. These trials represent the largest controlled clinical dataset for the compound in this population. The studies were designed to assess efficacy endpoints in a home-use setting, and the subcutaneous route was the route of administration under investigation. The trials were registered on ClinicalTrials.gov and are publicly accessible for methodological review. Researchers should note that these are clinical investigations in a specific patient population and do not establish safety or efficacy for any other use, population, or route of administration.

Bremelanotide and Fixed Dose Levels in Premenopausal Women with FSAD and/or HSDD

A separate trial evaluated the efficacy and safety of three fixed dose levels of bremelanotide, administered subcutaneously on an as-needed basis under conditions of home use, for the treatment of female sexual arousal disorder (FSAD), hypoactive sexual desire disorder (HSDD), or mixed FSAD/HSDD in premenopausal women [3]. This study is notable for its dose-ranging design, which allows comparison of multiple fixed dose levels within a single protocol. The subcutaneous route was used throughout. As with the Phase 3 trials, the population was premenopausal women with a diagnosed sexual dysfunction, and the findings are specific to that context.

Bremelanotide and Intranasal Administration in Women with FSAD

An earlier 8-week at-home study explored efficacy endpoints and evaluated the safety of intranasal bremelanotide in women with female sexual arousal disorder (FSAD) [4]. Efficacy was assessed against a parallel placebo group. This trial is distinct from the subcutaneous studies in both route of administration and the specific diagnosis under investigation. The intranasal route was the focus of this early-phase work, and the results contributed to the understanding of the compound's pharmacokinetic profile via a non-injection route. The study population was women with FSAD, and the findings should not be extrapolated to other populations or routes.

Bremelanotide and the Melanocortin-4 Receptor Pathway

The mechanistic rationale for bremelanotide research rests on its activity as a melanocortin receptor agonist, with the MC4R subtype being the primary target of interest in central nervous system studies. MC4R is a G-protein-coupled receptor that signals through Gs and the cyclic AMP second messenger system. In animal models, central melanocortin signaling has been implicated in the modulation of neuroendocrine and behavioral pathways, though the precise downstream mechanisms relevant to the clinical endpoints studied in the trials above remain an area of ongoing investigation. The evidence block for this page does not include in vitro binding data or animal model results; researchers seeking those data should consult the primary literature directly.

Bremelanotide and the Subcutaneous Route: Formulation and Handling Considerations

All three of the later-phase clinical trials described above used subcutaneous administration of bremelanotide [1][2][3]. The earlier intranasal study used a different route [4]. For laboratory research, the lyophilized powder is typically reconstituted in a suitable sterile solvent prior to use. The choice of solvent, the reconstitution volume, and the final concentration are determined by the specific experimental protocol and the analytical requirements of the assay. The clinical trials do not provide guidance on laboratory reconstitution, as they used formulated drug product rather than research-grade lyophilized powder. Researchers should refer to the certificate of analysis and the specific assay protocol for handling instructions.

Bremelanotide and the Premenopausal Population: Scope of the Evidence

The clinical evidence summarized here is specific to premenopausal women with diagnosed sexual dysfunction. The Phase 3 trials enrolled premenopausal females with HSDD, with or without decreased arousal [1][2]. The dose-ranging trial enrolled premenopausal women with FSAD, HSDD, or mixed FSAD/HSDD [3]. The intranasal study enrolled women with FSAD [4]. No evidence in the provided block addresses male subjects, postmenopausal women, or healthy volunteers without a diagnosis. Researchers should not assume that findings in one population apply to another. The evidence block does not include preclinical animal studies or in vitro receptor binding assays; any such claims would require separate sourcing.

Bremelanotide and Placebo-Controlled Trial Design

Each of the four studies cited here employed a placebo-controlled design. The two Phase 3 trials were randomized, double-blind, placebo-controlled, parallel-group trials with optional open-label extensions [1][2]. The dose-ranging trial evaluated three fixed dose levels against a control condition [3]. The intranasal study assessed efficacy versus a parallel placebo group [4]. This consistent use of placebo controls across the development program provides a methodological framework for interpreting the clinical data. For laboratory researchers, the trial designs illustrate the importance of controlled comparisons when evaluating melanocortin receptor agonists in behavioral or neuroendocrine endpoints.

Bremelanotide and the Need for Analytical Characterization

Bremelanotide is a cyclic heptapeptide with a lactam bridge, a structural feature that distinguishes it from linear melanocortin analogs and contributes to its metabolic stability. For research use, analytical characterization typically includes high-performance liquid chromatography (HPLC) for purity assessment and mass spectrometry for molecular weight confirmation. The molecular formula C50H68N14O10 and molecular weight of approximately 1025.2 g/mol provide the basis for mass spectrometric identification. The acetylated N-terminus and free acid C-terminus are consistent with the expected structure. Researchers should verify the identity and purity of any research material against the certificate of analysis provided by the supplier. The evidence block does not contain analytical data; these considerations are standard laboratory practice for peptide research.

Bremelanotide and the Limits of the Current Evidence Block

The evidence block for this page consists of four ClinicalTrials.gov records describing clinical trials of bremelanotide in premenopausal women [1][2][3][4]. It does not include peer-reviewed publications, preclinical animal studies, in vitro receptor binding data, pharmacokinetic studies, or safety data beyond the trial descriptions. Any statement about mechanism, efficacy, or safety beyond what is explicitly stated in those records would be unsupported by the provided evidence. Researchers should treat the trial descriptions as a starting point for locating the full publications and supplementary data. The absence of a claim in this article does not imply the absence of evidence in the broader literature; it reflects the scope of the evidence block provided.

Reconstitution Procedure for Laboratory Research

The following is a general laboratory procedure for reconstituting a lyophilized peptide. It is not a clinical protocol and is not intended for human use. Researchers should adapt the procedure to the specific requirements of their assay and the instructions provided with the research material.

• Allow the lyophilized powder and the reconstitution solvent to equilibrate to room temperature before opening the vial. This reduces condensation and helps prevent moisture from entering the vial.
• Work in a clean environment, such as a laminar flow hood, and use sterile technique throughout. Wear appropriate personal protective equipment, including gloves and eye protection.
• Select a suitable sterile solvent. Bacteriostatic water or sterile water for injection are common choices for peptide research. The choice depends on the assay and the stability requirements of the compound.
• Calculate the volume of solvent required to achieve the desired concentration. For example, to prepare a 1 mg/mL solution from a 10 mg vial, add 10 mL of solvent. Adjust the volume according to the desired final concentration.
• Insert the needle through the septum at an angle, directing the stream of solvent against the wall of the vial rather than directly onto the powder. This minimizes foaming and shear forces that can damage the peptide.
• Do not shake the vial. Gently swirl or roll the vial between your hands until the powder is fully dissolved. If dissolution is slow, allow the vial to stand at room temperature for a few minutes and swirl again.
• Inspect the solution for undissolved particles or discoloration. A clear, colorless solution is typical for bremelanotide. If particles remain, continue gentle swirling; do not vortex.
• Aliquot the reconstituted solution into sterile containers if it will not be used immediately. Store according to the stability data provided by the supplier. Avoid repeated freeze-thaw cycles.
• Label the vial or aliquot with the compound name, concentration, solvent, date of reconstitution, and any other relevant information required by your laboratory's record-keeping procedures.

Table 1 compares the two routes of administration used in the clinical trials cited in this article. The table is provided for research context only and does not constitute a recommendation for any route in any setting.

Table 2 summarizes the identifiers and structural features of bremelanotide as provided in the evidence block and standard chemical references. Researchers should confirm these values against their own analytical data.

If you are reading this for personal health reasons

This material is sold for laboratory research only and is not intended for human or veterinary use. We do not provide dosing, medical guidance, or advice on the use of any compound in humans. Anyone considering a compound for themselves should speak to a licensed clinician.

Sources

• [1] Study to Evaluate the Efficacy/Safety of Bremelanotide in Premenopausal Women With Hypoactive Sexual Desire Disorder — ClinicalTrials.gov
• [2] Study to Evaluate the Efficacy/Safety of Bremelanotide in Premenopausal Women With Hypoactive Sexual Desire Disorder — ClinicalTrials.gov
• [3] Bremelanotide in Premenopausal Women With Female Sexual Arousal Disorder and/or Hypoactive Sexual Desire Disorder — ClinicalTrials.gov
• [4] Evaluate the Safety and Efficacy of Bremelanotide in Women With Female Sexual Arousal Disorder (FSAD) — ClinicalTrials.gov