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PT-141 (Bremelanotide)

Melanocortin Receptor Agonist Research Reagent | Cyclic Heptapeptide | RUO

7 Amino Acids | MW ~1,025 g/mol | PubChem CID 9941379 | CAS 189691-06-3 | Sequence: Ac-Nle-cyclo(Asp-His-D-PheArg-Trp-Lys)-OH | Lyophilized | COA Per Batch

FOR RESEARCH USE ONLY. Not intended for consumption, parenteral administration, therapeutic, or diagnostic application of any kind. For laboratory and preclinical research exclusively.

TECHNICAL SPECIFICATIONS

Disclaimer : For Research Use Only (RUO). Not for human use.

PRODUCT OVERVIEW

PT-141 (bremelanotide) was rationally developed from early melanotan research as a structurally optimised melanocortin agonist for receptor pathway investigation. The compound is a cyclic heptapeptide with molecular formula C50H68N14O10 and molecular weight approximately 1,025 g/mol (PubChem CID 9941379; CAS 189691-06-3; DrugBank DB11653; KEGG DRUG D06569; ChemSpider 8116997). The cyclic lactam bridge between Asp and Lys residues, N-terminal acetylation of norleucine (Nle), and D-phenylalanine (D-Phe) substitution at position 4 collectively produce a conformationally constrained scaffold with enhanced metabolic stability and selective receptor engagement compared to linear alpha-MSH analogues.

The compound was extensively characterised in published preclinical and clinical pharmacology studies. FDA chemistry review documentation describes bremelanotide acetate , the salt form used in the approved pharmaceutical product Vyleesi — as a synthetic cyclic heptapeptide with the equivalency statement 1.75 mg bremelanotide base = 1.89 mg bremelanotide acetate. This distinction between the free base (PubChem CID 9941379) and the acetate salt (PubChem CID 91971505; acetate hydrate CID 169434958) is important for research purity specifications and molar concentration calculations. Profound Aminos supplies the research-grade free base form for laboratory use, not the pharmaceutical salt formulation.

The mechanistic profile of PT-141 in published preclinical research centres on central MC3R and MC4R agonism in hypothalamic and limbic circuits , pathways involved in neural circuit modulation research that are mechanistically distinct from peripheral nitric oxide synthase pathways. This central neuromodulatory mechanism makes PT-141 uniquely valuable for 2026-era research into melanocortin receptor pharmacology, hypothalamic neural circuit biology, and CNS receptor agonist tool compound studies.

MOLECULAR STRUCTURE – PubChem CID 9941379

PT-141 (Bremelanotide) – PubChem CID 9941379

Bremelanotide (PT-141) has molecular formula C50H68N14O10 and approximate molecular weight 1,025 g/mol. The compound is a cyclic heptapeptide with the IUPAC name (3S,6S,9R,12S,15S,23S)-15-[(N-Acetyl-L-norleucyl)amino]-9-benzyl-6-{3-[(diaminomethylidene)amino]propyl}-12-(1H-imidazol-5-ylmethyl)-3-(1H-indol-3-ylmethyl)-2,5,8,11,14,17-hexaoxo-1,4,7,10,13,18-hexaazacyclotricosane-23-carboxylic acid. The sequence Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH contains a cyclised ring formed via a lactam bond between the side-chain carboxyl of Asp (position 2) and the side-chain amine of Lys (position 7). Three key structural features drive the pharmacological profile: the cyclic lactam constraint restricts conformational freedom, presenting the His-D-Phe-Arg-Trp pharmacophore in the receptor-binding orientation; D-Phe at position 4 replaces the native L-Phe of alpha-MSH to confer resistance to aminopeptidase cleavage; and N-terminal acetylation of Nle blocks aminopeptidase attack at the N-terminus, removing the methionine oxidation

liability of native alpha-MSH. CAS Registry Number 189691-06-3 is assigned to the bremelanotide free base; the acetate salt used in the approved pharmaceutical product is covered by distinct CAS documentation.

Key Chemical Identifiers

RESEARCH MECHANISM – 2026 LABORATORY APPLICATIONS

In 2026-era central neuromodulation, receptor pharmacology, and melanocortin pathway research, PT-141 is utilised to investigate the following mechanistic endpoints:

1. MC3R / MC4R Central Receptor Agonism — Binding Kinetics & Pathway Research
   Investigating how bremelanotide selectively binds melanocortin receptor subtypes — with principal activity at MC1R and MC4R and additional activity at MC3R and MC5R — in CNS-relevant cell models. Research applications include competitive radioligand displacement assays using [125I]-NDP-alpha-MSH, cAMP accumulation assays in MC4R-expressing HEK293 cell lines (receptor activation via adenylate cyclase/PKA pathway), isoform-selective receptor binding profiling, and structure-activity relationship (SAR) studies comparing cyclic vs linear melanocortin peptide scaffolds. Key published reference: Molinoff PB et al., Expert Opin Investig Drugs 2003 (PMID: 12851303).
2. Hypothalamic Neural Circuit Modulation — MC4R Pathway Research
   Studying how MC4R agonism by PT-141 modulates neuronal activity in hypothalamic and limbic circuits involved in motivational and autonomic regulation. Research applications include electrophysiological recordings in hypothalamic slice preparations, calcium imaging in MC4R-expressing neuronal models, c-Fos immunohistochemistry mapping of MC4R-active neural circuits, and in vitro neuronal firing rate assays. Based on published PNAS mechanistic data (van der Ploeg LHT et al. 2002) and the 2022 J Clin Invest fMRI crossover study (PMID: 36189794) demonstrating MC4R-mediated neural circuit engagement in human research participants.
3. Cyclic Peptide Stability & DPP-IV Resistance Research
   Investigating the enzymatic stability profile of the cyclic lactam scaffold — particularly the contribution of D-Phe at position 4 (preventing aminopeptidase cleavage), the lactam bridge (providing conformational rigidity), and N-Ac-Nle N-terminus (blocking N-terminal exopeptidase attack). Research applications include in vitro peptide degradation assays in simulated physiological conditions, mass spectrometry-based metabolite identification, comparative half-life assays versus linear alpha-MSH, and plasma stability profiling. Reference: FDA pharmacokinetics review documentation for bremelanotide — terminal half-life approximately 2.7 hours subcutaneous; hydrolysis of amide bonds as primary metabolic pathway.
4. Melanocortin Receptor Subtype Selectivity Research — MC1R vs MC4R Dissection
   Quantifying the differential contributions of MC1R and MC4R engagement by PT-141 in tissue-specific research models. MC1R expression on melanocytes is responsible for the hyperpigmentation signal documented in published clinical programmes; MC4R in hypothalamic nuclei is the mechanistically relevant receptor for central circuit modulation research. Research applications include isoform-selective receptor reporter systems, MC1R vs MC4R competitive displacement assays, skin melanocyte vs neuronal cell line comparison studies, and targeted MC4R knockout model pharmacology. Key reference: FDA prescribing information documenting non-selective MCR agonism with MC1R and MC4R as therapeutically relevant subtypes.
5. Central Autonomic Regulation Research — Blood Pressure & Heart Rate Pathway
   Studying how central melanocortin receptor activation modulates autonomic cardiovascular regulation. Published clinical pharmacology data from the bremelanotide ambulatory blood-pressure characterisation programme (White WB et al., J Hypertens 2017, PMID: 27977473) documented placebo-subtracted systolic BP increases of approximately 3.1 mmHg at the 1.75 mg dose level and heart rate reductions of approximately 4.6-4.7 bpm — mechanistically consistent with MC4R-mediated central autonomic circuit modulation. Research applications include cardiovascular parameter telemetry in rodent melanocortin research models, MC4R antagonist reversal studies, and hypothalamic autonomic nuclei electrophysiology.
6. Cyclic Heptapeptide Conformational Pharmacology — SAR Research
   Investigating the structure-activity relationship contributions of individual PT-141 residues to MC receptor binding affinity and selectivity. The His-D-Phe-Arg-Trp tetrapeptide pharmacophore — corresponding to the core binding motif of alpha-MSH — is the primary receptor-contact region. Research applications include alanine-scan peptide analogue synthesis and binding comparison, Trp indole ring modification effects on MC4R affinity, Arg guanidinium group contribution to receptor pocket interaction, and cyclic vs linearised scaffold affinity comparison. Reference: Diamond LE et al., Int J Impot Res 2004 (PMID: 14963471) for early structure-activity characterisation.
7. Oral Bioavailability & Gastrointestinal Absorption Research
   Investigating how cyclic peptide architecture affects gastrointestinal stability and oral absorption in preclinical research models. FDA pharmacokinetics review documents a 100% subcutaneous bioavailability profile with peptide hydrolysis as primary metabolism and urinary/faecal excretion (64.8% / 22.8% radioactive recovery respectively). Research applications include Caco-2 intestinal permeability assays, in vitro gastrointestinal enzyme stability profiling, oral vs subcutaneous bioavailability comparison in rodent models, and P-glycoprotein efflux studies relevant to cyclic peptide CNS penetration research.
8. Gastric Motility & GI Absorption Interaction Research
   Studying how MC receptor engagement by PT-141 modulates gastric emptying rate and its consequences for concomitant oral research compound absorption ,a mechanistically documented pharmacodynamic interaction pathway based on FDA-published clinical pharmacology data showing bremelanotide slows gastric motility. This positions PT-141 as a research tool for investigating melanocortin receptor involvement in gastrointestinal motility regulation. Research applications include gastric emptying radiotracer studies, duodenal absorption rate measurements, and pharmacokinetic interaction modelling of melanocortin agonism on GI transit time.v

WHY SOURCE FROM PROFOUND AMINOS

1. Cyclic Structure Verification via LC-MS — Beyond Linear Purity Testing
   Standard RP-HPLC purity testing confirms what percentage of a container is the target compound it does not confirm whether the cyclic lactam bridge is correctly formed. PT-141 contains a lactam bond between Asp (position 2) and Lys (position 7); an incorrectly cyclised or linearised byproduct from synthesis can have similar RP-HPLC retention times to the target cyclic compound while having fundamentally different receptor pharmacology. Profound Aminos verifies every batch via LC-MS molecular weight confirmation (expected [M+H]+ ~1026 for free base) and structural confirmation consistent with the cyclic scaffold. Purity without cyclic structure verification is an incomplete quality standard for this class of peptide.
2. Lyophilized Format — Critical for Tryptophan Stability
   Trp at position 6 of PT-141 contains an indole side chain that is susceptible to oxidation in aqueous solution, particularly under light exposure or thermal stress , generating kynurenine and related oxidation products that alter receptor binding affinity. Lyophilization removes aqueous solvent, dramatically slowing Trp oxidation pathways and extending the functional research lifetime of the compound. Every Profound Aminos PT-141 batch is lyophilized and stored in light-protected, desiccated conditions. Reconstituted aliquots should be used promptly and protected from UV exposure.
3. Endotoxin Screening — Critical for CNS Research Models
   Lipopolysaccharide (LPS) endotoxin activates TLR4/NF-kB signalling in glial cells and neuronal preparations, generating pro-inflammatory cytokines that can confound or mimic melanocortin receptor-mediated CNS pathway research outcomes. For researchers investigating MC4R-mediated hypothalamic neural circuit modulation, unscreened endotoxin contamination is a direct research validity threat — indistinguishable from receptor-mediated effects without dedicated control experiments. Every Profound Aminos PT-141 batch is screened to <0.25 EU/mg by LAL chromogenic method, documented on the per-batch COA.
4. USA Domestic Cold-Chain — Trp Oxidation and Peptide Integrity
   International sourcing introduces uncontrolled temperature excursions during customs transit that accelerate Trp indole oxidation and amide bond hydrolysis — degrading the cyclic scaffold that is essential to PT-141’s receptor binding geometry. Profound Aminos ships exclusively within the USA via a monitored cold-chain logistics protocol from a climate-controlled facility to the research address, eliminating international transit degradation risk.

COMPARATIVE RESEARCH CONTEXT – 2026 Melanocortin Receptor Agonist Research Landscape

Important Note : Profound Aminos supplies PT-141 (Bremelanotide) strictly as an RUO research reagent — NOT as the FDA-approved pharmaceutical product Vyleesi. The approved product is manufactured by Palatin Technologies under strict pharmaceutical GMP as a 1.75 mg/0.3 mL sterile subcutaneous autoinjector. Profound Aminos RUO material is a research reagent governed by 21 CFR 312.2(b)(1), not a pharmaceutical product. These are legally distinct categories.

FREQUENTLY ASKED QUESTIONS

Q1: Is PT-141 (Bremelanotide) from Profound Aminos the same as the FDA-approved drug Vyleesi?

No — these are legally and materially distinct products. Vyleesi is the FDA-approved pharmaceutical product manufactured by Palatin Technologies under pharmaceutical GMP as bremelanotide acetate 1.75 mg/0.3 mL sterile subcutaneous autoinjector (NDA 210557, approved 21 June 2019). Profound Aminos supplies PT-141 (Bremelanotide) as a lyophilized Research Use Only (RUO) reagent governed by 21 CFR 312.2(b)(1). The RUO reagent is not a pharmaceutical product, is not FDA-approved for any application, is not compounded under 503A/503B frameworks, and is not intended for administration to living organisms. Purchase confirms agreement to institutional laboratory research use only.

Q2: What are the key PubChem chemical identifiers for PT-141 (Bremelanotide)?

Bremelanotide free base: PubChem CID 9941379 | Molecular Formula C50H68N14O10 | MW ~1,025 g/mol | CAS 189691-06-3 | DrugBank DB11653 | KEGG DRUG D06569 | ChemSpider 8116997 | ChEMBL CHEMBL2104001. Bremelanotide acetate salt: PubChem CID 91971505. Bremelanotide acetate hydrate: PubChem CID 169434958. The free base and acetate forms are distinct compounds with different molecular formulae and molecular weights — the active peptide sequence is identical, but the counter-ion and molecular weight differ. All records are accessible at pubchem.ncbi.nlm.nih.gov.

Q3: What is the mechanism of action of PT-141 (Bremelanotide) in research models?

Bremelanotide is a non-selective melanocortin receptor (MCR) agonist with principal activity at MC1R and MC4R and additional activity at MC3R and MC5R. FDA’s prescribing information states the mechanism by which Vyleesi improves HSDD in women is unknown, but published translational and mechanistic research supports a central MC4R-mediated pathway. MC4R receptors are expressed in hypothalamic and limbic circuits involved in autonomic regulation and motivational processing. MC1R expression on melanocytes explains the hyperpigmentation signal documented in clinical development. The cyclic lactam scaffold restricts conformational flexibility, presenting the His-D-Phe-Arg-Trp pharmacophore in the receptor-binding geometry required for high-affinity MCR interaction. This central mechanism distinguishes PT-141 from peripheral vasodilator compounds in research applications.

Q4: What is the FDA regulatory status of PT-141 (Bremelanotide) in May 2026?

Bremelanotide (as Vyleesi) holds FDA NDA 210557, approved 21 June 2019, for acquired, generalised hypoactive sexual desire disorder (HSDD) in premenopausal women. The approved indication explicitly excludes postmenopausal women, men, and sexual-performance enhancement. As of May 2026, no additional FDA-approved indications exist. Ongoing programmes (diabetic kidney disease NCT05709444; obesity combination NCT06565611) remain investigational and non-approved.

Regarding compounding: PT-141/bremelanotide is not on the FDA 503A or 503B positive bulks lists for compounding , it is an FDA-approved active ingredient in a branded product (Vyleesi), and compounding of essentially-copy preparations of FDA-approved drugs is subject to specific statutory restrictions. The Profound Aminos RUO reagent is not a compounded pharmaceutical and is not the approved product. It is supplied exclusively as a research reagent under 21 CFR 312.2(b)(1).

Q5: What published clinical research exists for PT-141 (Bremelanotide)?

A substantial clinical development programme was conducted and published. Key studies include: Phase IIb dose-finding in premenopausal women with FSD/HSDD (Clayton et al. 2016, Womens Health, PMID: 27181790) — 612 enrolled; Phase III RECONNECT pivotal trials — two identical 24-week randomised controlled trials in 1,247 premenopausal women meeting both co-primary FSFI-Desire and FSDS-DAO endpoints (Kingsberg et al. 2019, PMID: 31599840);

52-week open-label extension safety study (Simon et al. 2019, PMID: 31599847); 2022 fMRI crossover mechanistic study demonstrating MC4R-mediated neural circuit engagement in women with HSDD (Thurston et al. 2022, PMID: 36189794); cardiovascular characterisation study (White et al. 2017, PMID: 27977473); and integrated safety analysis across 43 studies, 3,500 subjects (Clayton et al. 2022, PMID: 35147466). All clinical data are from the FDA-approved product Vyleesi, not from RUO research reagents. RUO material is not to be used for human application.

Q6: How is PT-141 (Bremelanotide) reconstituted for laboratory research use?

Reconstitute lyophilized PT-141 in sterile PBS or bacteriostatic water at the molar concentration required for the specific assay protocol. Use MW ~1,025 g/mol (free base) for concentration calculations. Add solvent slowly along the inner wall of the container using gentle swirling — do not vortex. Aliquot immediately into single-use research volumes and store at -20 degrees C. Protect from light at all steps to prevent Trp indole oxidation. Avoid repeated freeze-thaw cycles which accelerate cyclic peptide degradation. Inspect visually before use and discard any preparation showing turbidity or colour change. Consult the batch COA for specific purity, endotoxin, and storage recommendations.

Q7: What analytical quality controls does Profound Aminos perform on PT-141?

Every PT-141 batch from Profound Aminos is verified by: RP-HPLC purity (>=99%); LC-MS identity confirmation — molecular weight verification consistent with free base C50H68N14O10 (~1,025 g/mol) and structural characterisation consistent with cyclic scaffold; endotoxin screening (<0.25 EU/mg by LAL chromogenic method); lot number and manufacturing date documentation. All data reported on the per-batch Certificate of Analysis, downloadable from the Profound Aminos COA portal prior to or upon order.

Q8: What is the pharmacokinetic profile of Bremelanotide from published FDA review data?

FDA clinical pharmacology review (NDA 210557) documents the following for the approved subcutaneous formulation: absolute bioavailability approximately 100%; median Tmax approximately 1.0 hour; mean plasma Cmax 72.8 ng/mL; AUC 276 hour*ng/mL; protein binding 21%; mean volume of distribution 25.0 +/- 5.8 L; terminal half-life approximately 2.7 hours; clearance 6.5 +/- 1.0 L/hour; metabolism by multiple amide bond hydrolysis rather than dominant CYP pathway; radiolabel recovery 64.8% urine and 22.8% faeces. Exposure increases in organ impairment: AUC increased 1.2-fold (mild renal), 1.5-fold (moderate renal), 2.0-fold (severe renal); 1.2-fold (mild hepatic), 1.7-fold (moderate hepatic). These pharmacokinetic parameters are published for the FDA-approved pharmaceutical product and are presented here as reference data for research context, not as guidance for any non-approved use.

Q9: What are the key safety findings from published clinical programmes?

The safety profile from pooled phase III placebo-controlled data (3,500 subjects across 43 studies; Clayton et al. 2022, PMID: 35147466) documents: nausea 40.0%, flushing 20.3%, injection-site reactions 13.2%, headache 11.3%, vomiting 4.8%, cough 3.3%, fatigue 3.2%, hot flush 2.7%, paraesthesia 2.6%, dizziness 2.2%, nasal congestion 2.1%. Cardiovascular: transient blood pressure increase (maximum approximately 6 mmHg systolic, 3 mmHg diastolic, peaking 2-4 hours post-dose) with heart rate reduction up to 5 bpm — contraindicated in uncontrolled hypertension and known cardiovascular disease.

Focal hyperpigmentation: in 1% of patients receiving up to 8 monthly doses (38% under daily dosing for 8 days), more frequent in patients with darker skin, not always resolved after discontinuation. These findings are from the approved product clinical programme and are research-context information only.

Q10: Can PT-141 (Bremelanotide) be compounded under 503A or 503B for human use?

This requires careful distinction. Bremelanotide is an active ingredient in FDA-approved Vyleesi (NDA 210557). Compounding of essentially-copy preparations of FDA-approved drugs is subject to significant statutory restrictions under 21 U.S.C. 353a and 353b. Unlike bulk drug substances on the 503A positive bulks list, bremelanotide compounding involves a different regulatory analysis because an approved reference product exists.

Some 503A pharmacies have compounded bremelanotide for patient-specific off-label indications (such as male ED) with valid prescriptions, but this involves navigating the ‘essentially a copy’ prohibition and requires documented clinical rationale for the individual patient. The Profound Aminos RUO reagent is not a compounded pharmaceutical. It is a research-grade material supplied exclusively for laboratory investigation under 21 CFR 312.2(b)(1) and is not to be used for human application under any circumstances.

REGULATORY & COMPLIANCE STATEMENT (RUO)

STRICT PROHIBITION : Promoting, distributing, or using this research reagent for any application involving administration to living organisms is strictly prohibited and constitutes a violation of U.S. federal law. FDA enforcement actions in 2024-2026 have established that RUO disclaimers do not protect vendors when overall marketing content indicates intended human use.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

KEY REFERENCES – PubMed / PubChem / FDA Verified

FOR RESEARCH USE ONLY. Not intended for consumption, parenteral administration, therapeutic, or diagnostic application of any kind. For laboratory and preclinical research exclusively.

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