Quantitative Chiral Separations on KRAS Inhibitor Sotorasib by UHPLC‐MS/MS: Method Validation and Enantioselective Pharmacokinetics Assessment in Rat Plasma

In this research, estimation of enantioselective pharmacokinetics and biological interconversion of sotorasib were investigated. This is the first report for the novel chiral liquid chromatography-tandem mass spectrometry method for the enantioselective pharmacokinetics determination in biological matrix. Attempts were made to achieve separation in reverse phase mode with mass compatible mobile phase. The baseline chiral separation was achieved with a mobile phase consisting of acetonitrile and aqueous ammonium bicarbonate (15 mM; 95/5 v/v) on Chiralpak IC (250 × 4.6 mm, 5 μm). Positive electrospray ionization was used for monitoring multiple reactions by triple quadrupole. The developed bioanalytical method was validated for each SOT enantiomer, assessing selectivity and specificity, linearity, accuracy, precision, recovery, matrix effect, dilution integrity, and stability. The lower limit of quantification was identified as 1 ng/mL for both SOT enantiomers. The results were found to be in compliance with the bioanalytical method validation guideline. The preclinical study revealed the disparate pharmacokinetic profile between the (R) and (S)-sotorasib, after single oral administration (10 mg/kg) to rats. This is the first investigational evidence of enantioselective behavior of sotorasib in vivo. The results demonstrated that lower maximum concentration, area under curve, and higher clearance and volume of distribution for (R)-sotorasib reveal the poorer bioavailability and higher elimination rate. The study provides insights in controlling the enantiomeric impurity in quality control aspects. This research also provides a reference for clinical practice and supports further research in distomer toxicity, enantioselective drug metabolism, and drug interactions.