Development and optimization of a high-throughput HPLC-MS/MS method for the simultaneous determination of Cedazuridine, Gemcitabine and its metabolite in mouse plasma

Gemcitabine (GEM) has been extensively applied in treating various solid tumors. Nonetheless, GEM is easily metabolized in vivo by cytidine deaminase (CDA) to inactive 2', 2'-Difluorodeoxyuridine (dFdU) results in a low oral bioavailability, which limit its clinical application. It was found that Cedazuridine (CDZ) could effectively inhibit the deamination of the drug by CDA, and its combination with GEM might affect the oral bioavailability of GEM. To investigate the effect of CDZ on the bioavailability and metabolism of GEM after oral administration, an HPLC-MS/MS method was developed for the simultaneous determination of CDZ, GEM, and its metabolite dFdU in mouse plasma. The separation of CDZ, GEM and dFdU was performed on an acetonitrile and water containing 0.1 % formic acid in isocratic elution on a COSMOSIL® 5C18-PAQ packed column (150 × 4.6 mm, 2.6 µm). The three analytes and the internal standard were determined in a multiple reaction monitoring (MRM) mode under positive ion conditions. The three analytes showed good linearity in the range of 5-10,000 ng/mL, and all quality control samples showed good precision and accuracy. The method was successfully applied to the pharmacokinetic study of GEM with CDZ. The results showed that CDZ significantly improved the oral bioavailability of GEM by reducing the metabolism of CDA to GEM in mice, which will provide a reference for the combined application of GEM and CDZ in clinical therapy.