A reliable and stable method for the determination of foretinib in human plasma by LC-MS/MS: Application to metabolic stability investigation and excretion rate.

Foretinib (GSK1363089) is a multiple receptor tyrosine kinases inhibitor. In this study, a reliable, fast liquid chromatography-tandem mass spectrometric method was described for assaying foretinib in plasma, urine, and rat liver microsome samples. Simple extraction procedure by protein preciptation with acetonitrile was implemented for foretinib and brigatinib (internal standard) analysis. Chromatographic resolution of analytes was achieved on C18 column with the help of isocratic mobile phase. The binary mobile phase consisted of 60% ammonium formate (10 mM, pH 4.2) and 40% acetonitrile at a flow rate of 0.25 mL/min. Run time was 3 min, and both foretinib and brigatinib were eluted within 0.74 and 1.95 min; they were detected in positive ion mode utilizing multiple reactions monitoring mode. Linearity of the proposed method ranged from 5 to 500 ng/mL (r2 ≥ 0.9993) in the human plasma. Lower limit of quantification and detection were 6.0 and 1.8 ng/mL, respectively. Intraday and interday precision and accuracy were 0.16 to 1.67 % and -2.39 to -0.52 %. In vitro half-life and intrinsic clearance were 24.93 min and 6.56 mL/min/kg, respectively. Literature review showed that no previous studies have been proposed for the analytical quantification of foretinib in human plasma or its metabolic stability. The established method was also applied to estimate the rate of foretinib excretion in rat urine. The developed method can be used for foretinib pharmacokinetic applications.