UPLC-MS/MS analysis of axitinib and pharmacokinetic application in beagle dogs

To develop a method for determining the concentration of axitinib in beagle dog plasma and utilize this method to investigate the pharmacokinetics of orally administered axitinib in beagle dogs.

Plasma samples were processed using acetonitrile precipitation and analyzed by UPLC-MS/MS with sunitinib as an internal standard (IS). Chromatographic separation was achieved on a Waters Acquisition UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm) with a gradient elution of acetonitrile and 0.1 % formic acid. Mass spectrometry uses an electrospray ion source for positive ion detection in a multiple reaction monitoring mode. The monitored ion transitions for axitinib and sunitinib were m/z 387 → 355.96 and m/z 399.3 → 282.96, respectively. Six beagle dogs were administered 0.33 mg/kg of axitinib orally, and venous blood samples were collected at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 h post-dose for pharmacokinetic analysis.

The assay demonstrated a linear range of 0.5-100 ng/mL (r² = 0.9992), and the lower limit of quantification was up to 0.5 ng/mL. Precision, as assessed by relative standard deviation (RSD), was within 8.64 % for both intraday and interday variability. The relative error (RE) for precision from -2.77 %-1.20 %. The recovery rate of the analytes exceeded 85.28 % and the matrix effect was approximately 100 %. Plasma samples maintained stability under various conditions, including room temperature storage for 12 h, processed on an automatic sampler at 4 °C for 6 h, three freeze-thaw cycles, and long-term storage at -80 °C for 60 days. Pharmacokinetic parameters were determined using DAS 2.0 software, revealing a half-life (T_1/2) of 6.05 h and an area under the curve (AUC _{(0 → ∞)}) of 97.13 ng h/mL for axitinib.

The UPLC-MS/MS method developed in this study offers high specificity, rapid analysis, high recovery, excellent linearity, and minimal plasma volume requirements, making it well-suited for pharmacokinetic and drug interaction studies in beagles dogs.