Abarelix Acetate | CAS 785804-17-3 / 183552-38-7 | GnRH Receptor Antagonist (Research Use Only) | Knowlux

Product Description

Abarelix Acetate, CAS 785804-17-3 (acetate salt) / 183552-38-7 (free peptide), is a synthetic linear decapeptide gonadotropin-releasing hormone (GnRH) receptor antagonist supplied by Knowlux for laboratory research use. The sequence is Ac-D-2Nal-D-Phe(4-Cl)-D-3Pal-Ser-N(Me)Tyr-D-Asn-Leu-Lys(iPr)-Pro-D-Ala-NH2. The free peptide molecular formula is C72H95ClN14O14 (MW 1416.06); the acetate salt corresponds to C74H99ClN14O16 with a molecular weight of approximately 1476.12. Each lot is released with a lot-specific COA, MSDS and analytical traceability.

CAS and Salt Form Distinction: The CAS landscape for Abarelix is a frequent source of procurement ambiguity. CAS 183552-38-7 is the free peptide registry and is the identifier most widely applied across PubChem, NCI Thesaurus, and ChemicalBook listings. CAS 785804-17-3 is the acetate salt registry, and it is the more precise identifier when the counter-ion basis must be documented explicitly for assay or regulatory purposes. A substantial number of supplier catalogues use 183552-38-7 under the product name "Abarelix Acetate," conflating the free peptide and salt registries. Knowlux specifies the salt basis, acetate content, and water content per lot on the COA. Buyers should confirm whether the quoted material is reported on a free-peptide or acetate-salt basis before procurement, as the acetate counter-ion shifts the mass balance by approximately 60 g/mol.

Structural Note: The decapeptide backbone incorporates several non-natural residues that distinguish Abarelix from native GnRH: D-2-naphthylalanine at position 1, D-4-chlorophenylalanine at position 2, D-3-pyridylalanine at position 3, N-methyltyrosine at position 5, and N6-isopropyllysine at position 8. The N-terminus is acetylated and the C-terminus is D-alaninamide (D-Ala-NH2). Unlike the disulfide-constrained peptides in the Ziconotide and Linaclotide families, Abarelix is linear and does not contain cysteine residues. The multiple D-amino acid substitutions and the N-methylated tyrosine are the structural determinants of its antagonist activity and metabolic stability.

Product Parameters

Product Details

1. Overview

Abarelix is a synthetic decapeptide that functions as a direct and competitive antagonist at the pituitary GnRH receptor. Unlike GnRH superagonists (e.g., leuprolide, goserelin), which initially stimulate gonadotropin release before receptor downregulation, Abarelix produces immediate suppression of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion without an initial testosterone surge. This pharmacological distinction has made it a reference compound for studying GnRH receptor antagonism and for investigating hormone-dependent prostate cancer models. Abarelix was developed by Praecis Pharmaceuticals under the trade name Plenaxis and received FDA approval in 2003 for advanced prostate cancer. It was voluntarily withdrawn from the US market in 2006 due to an unacceptable rate of immediate-onset histamine-mediated hypersensitivity reactions. The material supplied under this specification is research-grade and is not intended for human administration. Knowlux supplies this compound strictly for laboratory investigation of GnRH receptor pharmacology, pituitary hormone regulation, and peptide immunogenicity.

2. Receptor Pharmacology and Histamine Release Liability

Abarelix binds the human GnRH receptor with high affinity and blocks LH and FSH release. GLPBIO reports an IC50 of 3.5 nM in HEK293 cells expressing the human GnRH receptor. The pharmacological profile is characterized by rapid onset of testosterone suppression to castrate levels without the flare phenomenon associated with GnRH agonists. A key safety-relevant pharmacological property of Abarelix, and a consideration for any research application involving mast cells or histamine-sensitive systems, is its histamine-releasing activity: Abarelix at concentrations of 30 and 300 ug/mL causes significantly increased histamine release in vitro, a property linked to the clinical hypersensitivity reactions that led to its market withdrawal. This liability is structurally associated with the peptide's overall cationic and amphipathic character and distinguishes it from later-generation GnRH antagonists such as degarelix, which were engineered to reduce histamine release.

3. Research Applications

Published pharmacological characterizations and documented protocols describe the following research applications:

• GnRH receptor binding and functional antagonist assays (LH/FSH suppression in pituitary cell models)

• Prostate cancer and hormone-dependent tumor growth research models

• Comparative pharmacology of GnRH agonists versus antagonists (absence of testosterone flare)

• Peptide-induced histamine release and hypersensitivity mechanism studies

• Reference standard development for HPLC and LC-MS analytical methods

These descriptions are derived from published research and are provided for scientific reference only. They do not constitute clinical guidance or dosing recommendations.

Quality Control

Supplier-reported purities for Abarelix Acetate span a range consistent with the grade offered. BenchChem lists purity >=97% by HPLC for its standard research grade. Selleck reports a batch-level HPLC purity of 99.32% and lists the catalogue specification as >=98.0%. MedChemExpress reports 99.61% for a representative lot. ChemicalBook supplier listings specify single impurity <=2.0%, peptide content >=80.0%, and water content <=8.0% for the research-grade acetate salt. The principal quality consideration is the distinction between HPLC area-percent purity and peptide content on an anhydrous, acetate-free basis; researchers preparing molar solutions should use the peptide content value rather than the HPLC purity figure. Full COA, MSDS, and lot-specific chromatograms are issued with each shipment.

Solubility and Handling

Solubility: Abarelix Acetate solubility is strongly solvent-dependent, and supplier data reflect this. DMSO is the preferred solvent across sources: BenchChem, Selleck, TargetMol, and MyBioSource report DMSO solubility of >=100 mg/mL (67.75 mM), with sonication recommended. Selleck additionally reports water solubility of 100 mg/mL and ethanol solubility of 10 mg/mL for its lot. In contrast, ChemicalBook describes the compound as sparingly soluble in methanol and water, and Anjiechem lists DMF 30 mg/mL, DMSO 30 mg/mL, ethanol 30 mg/mL, and PBS (pH 7.2) 5 mg/mL. These divergences likely reflect differences in salt form, lot history, and whether sonication was applied. For practical stock preparation, DMSO at >=100 mg/mL is the most consistently supported condition across sources; aqueous dilution should be performed immediately before use, and precipitation upon dilution into aqueous media has been documented as a handling consideration. Prepare solutions fresh and aliquot to avoid repeated freeze-thaw cycles.

Handling Precautions: Use powder-handling containment (glove box or fume hood with particulate control). Avoid inhalation of fine powder. Wear nitrile gloves, lab coat, and eye protection. BenchChem technical guidance notes that Abarelix Acetate can adsorb to common laboratory plastics, reducing effective concentration; low-binding polypropylene tubes and tips are recommended for assay work. The histamine-releasing property documented in the pharmacological literature warrants awareness when handling the compound in settings involving mast cells or histamine-sensitive assays.

Storage and Stability

Storage guidance converges on -20C as the standard long-term condition for the lyophilized powder, with desiccation and protection from moisture. TargetMol, Selleck, MyBioSource, and BenchChem all specify 3 years at -20C for powder. MedChemExpress offers a more conservative tier of 2 years at -80C and 1 year at -20C. Chem-Impex lists storage at 0C to 8C, an outlier relative to the -20C and -80C recommendations from the principal research-grade suppliers. For long-term archival storage, -20C under desiccation is the most widely supported condition. Reconstituted DMSO stocks are less stable than the powder: BenchChem recommends storage at -80C for no longer than 6 months, and MedChemExpress lists 1 month at -20C for solutions. Prepare aliquots to avoid repeated freeze-thaw cycles. Protect from light and moisture throughout storage.

Documentation Support

Per lot: COA, MSDS, certificate of origin, HPLC chromatogram, and mass spectrometry data. Acetate content, water content, peptide content, and counter-ion specification available on request. Custom specifications and third-party inspection can be arranged on a project basis.

About Knowlux

Knowlux Biotechnology is a GMP-oriented manufacturer and supplier of peptides, APIs and fine-chemical research compounds, operating from Hubei, China. We serve research groups, CDMOs and distributors in more than 40 countries, and support contract synthesis, custom packaging and technical documentation requests.

Compliance Statement

FOR RESEARCH USE ONLY. NOT FOR HUMAN USE. NOT FOR DIAGNOSTIC OR THERAPEUTIC USE.

This product is supplied for laboratory research use only. It is not for human or animal administration, not for diagnostic or therapeutic use, not for retail sale, and not for personal use. Abarelix is an approved medicinal product in certain jurisdictions for specific clinical indications (advanced prostate cancer); however, it was withdrawn from the US market in 2006, and the material offered under this specification is research-grade and is not intended for clinical use. The purchaser is responsible for verifying product specifications against their specific research requirements and for compliance with all applicable institutional, local, and national regulations governing research chemical acquisition, storage, and use. Research context statements are for scientific reference only and do not constitute medical advice, promotional claims, or dosing guidance.

Data Verification Notes: The molecular formula C72H95ClN14O14 and molecular weight 1416.06 for the free peptide are confirmed by PubChem, NCI Thesaurus, ChemicalBook, InvivoChem, and Santa Cruz Biotechnology. The acetate salt formula C74H99ClN14O16 and molecular weight 1476.12 are confirmed by Selleck, GLPBIO, EvitaChem, and Xcess Biosciences under CAS 785804-17-3. Chem-Impex lists the acetate as C72H95ClN14O14.C2H4O2 with MW 1476.13, which is stoichiometrically consistent with a monoacetate of the free peptide. One ChemicalBook listing shows a molecular weight of 2639.16 alongside formula C102H172N36O32S7; this is the formula and molecular weight of Ziconotide, not Abarelix, and is treated as a data entry error rather than adopted. The CAS mapping (785804-17-3 = acetate salt; 183552-38-7 = free peptide) is confirmed by InvivoChem, Selleck, GLPBIO, and EvitaChem. The IC50 of 3.5 nM (HEK293, human GnRH receptor) is from GLPBIO. The histamine release data (30 and 300 ug/mL) and the FDA withdrawal history are from ChemicalBook. Solubility values are reported with their source conditions rather than reconciled into a single figure because the underlying measurements reflect different salt forms, dissolution techniques, and solvent systems.

Formatting Note: All formulas, sequences, and comparison operators use plain ASCII notation to prevent character corruption on the platform. Section headings, table alignment, and spacing follow the approved product detail pattern. No trailing spaces or non-breaking characters are used; tables use consistent pipe alignment.