Development of Fast and Simple LC-ESI-MS/MS Technique for the Quantification of Regorafenib; Application to Pharmacokinetics in Healthy Rabbits

Background: A simple quantification technique by liquid chromatography electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) is required for regorafenib in biological matrices with bioavailability studies in healthy rabbits, when compared with reported techniques. Objective: The main aim of the research work was to develop a validated LC-ESI-MS/MS technique for the quantification of regorafenib and application to bioavailability studies in healthy rabbits. Methods: Chromatographic separation was achieved with hypersil-C-18 analytical column (50mmx4.6 mm, 4 mu m) and mobile phase composition of acetonitrile and 5mM ammonium acetate in the proportion of 70:30. The mobile phase was infused into the column with high pressure to get a 0.7 ml/min flow rate. The total retention time of the analyte is promising when compared with the existed methods for regorafenib. Quantitation was processed by monitoring transitions of m/z -483.0/262.0 and 450.0/260.0 for regorafenib and internal standard respectively in multiple reaction monitoring. Results: The linearity equation and correlation coefficient (R-2) findings were y =0.9948x+2.6624 and 0.998 respectively. The intra and inter-day precision of the developed technique was found between 1.00 - 8.50% for the QC-samples (2, 4, 240 and 480ng/ml). From bioavailability study, the drug was shown T-max of 3.688 +/- 0.754; average AUC(0 ->alpha) and AUC(0 -> t) were 6476.81 +/- 259.59 and 6213.845 +/- 257.892 respectively and C-max was found to be 676.91 +/- 22.045 in healthy rabbits. Conclusion: The developed technique was validated and successfully applied in the pharmacokinetic study of the drug (40 mg tablet) administered through the oral route in healthy rabbits.