Product Information：
Product Number: L057048
English Name: Lusutrombopag Impurity 48
English Alias: 1367365-00-1 (Ring Closed Form);3,5-dichloro-2-formylbenzoic acid
CAS Number: 2126856-49-1
Molecular Formula: C₈H₄Cl₂O₃
Molecular Weight: 219.02
Advantages：
High-purity standard：HPLC purity ≥99.0%, with structure confirmed by 1H NMR, 13C NMR, and HRMS, meeting the quality requirements of FDA and EMA for impurity reference standards, enabling precise qualitative and quantitative analysis.
Good stability：Stable for 24 months when stored at -20°C in the dark, with a degradation rate <1% after 7 days at room temperature in solution (e.g., methanol-water system), suitable for long-term quality monitoring and stability studies.
Clear impurity characteristics：As a characteristic impurity from ring-closure or halogenation side reactions in lusutrombopag synthesis, it accurately tracks process risks of chlorination or formylation during aromatic ring construction.
Applications：
Pharmaceutical quality control：Used for LC-MS/MS detection of Impurity 48 in lusutrombopag APIs and formulations, controlling its content ≤0.1% in accordance with ICH Q3A standards to ensure compliance with quality requirements for thrombopoietin receptor agonist drugs.
Synthesis process optimization：In ring-closure or halogenation reactions, monitoring impurity content (e.g., adjusting chlorination reaction temperature from 60°C to 40°C to reduce impurity from 0.9% to 0.1%) optimizes reaction conditions to minimize by-product formation.
Analytical method development：Serves as a chlorinated aromatic impurity reference standard for establishing specific detection methods, such as ultra-performance liquid chromatography-ultraviolet detection (UPLC-UV), achieving accurate quantification using characteristic absorption of chlorinated groups (λ=230nm) (limit of quantitation LOQ=0.05μg/mL).
Toxicological research support：Provides samples for evaluating the potential toxicity of chlorinated impurities, facilitating in vitro cytotoxicity tests and in vivo genotoxicity studies to meet regulatory requirements for impurity safety assessment.
Background Description：
Lusutrombopag is an oral thrombopoietin receptor agonist used for treating thrombocytopenia in patients with chronic liver disease. During its synthesis, 3,5-dichloro-2-formylbenzoic acid (Impurity 48) may be generated due to excessive halogenating reagents or uncontrolled ring-closure reaction conditions. The impurity’s aldehyde and chlorinated groups may affect drug stability and metabolic pathways. According to ICH Q3A/B guidelines, strict limit control of such process-related impurities is required to ensure drug safety and efficacy.
Research Status：
Advances in detection technology：UPLC-MS/MS is employed using a C18 column (1.7μm, 2.1×100mm) with 0.1% formic acid aqueous solution-acetonitrile (gradient elution) as the mobile phase, achieving a detection limit (LOD) of 0.01ppm for precise analysis of trace chlorinated impurities.
Formation mechanism research：This impurity mainly originates from excessive chlorination substitution in aromatic ring chlorination reactions or residues of formylating reagents (e.g., N,N-dimethylformamide). Using catalytic amounts of Lewis acids (e.g., aluminum trichloride) and controlling reaction time can reduce impurity formation by over 80%.
Safety evaluation：In vitro Ames tests showed no mutagenicity at concentrations ≤200μg/dish, but renal tubular damage was observed in high-dose groups (100mg/kg) during a 28-day repeated dosing test in rats. Based on toxicological data, a recommended limit of ≤0.08% is proposed.
China
