A Simple and Sensitive LC-MS/MS Method for the Determination of Mobocertinib and Its Metabolite Desmethyl-Mobocertinib in Human Plasma and Its Application to Clinical Pharmacokinetic Study

Mobocertinib is a potent selective tyrosine kinase inhibitor approved for the treatment of non-small cell lung cancer with activating EGFR exon 20 insertions. The aim of this study was to develop a procedure for liquid chromatography tandem mass spectrometry (LC-MS/MS) for the determination of mobocertinib and its metabolite desmethyl-mobocertinib in human plasma. The human plasma samples were precipitated with acetonitrile and analyzed using a Waters ACQUITY BEH C₁₈ column coupled to a triple quadrupole mass spectrometer. Separation was executed using the acetonitrile-0.1% formic acid solution with gradient elution, at a flow rate of 0.4 mL/min. Mobocertinib and desmethyl-mobocertinib were monitored by multiple reaction monitoring (MRM) with m/z 586.5 > 72.2 and 572.4 > 473.2, respectively. The procedure demonstrated excellent linearity (r > 0.997) within the concentration range of 0.1-200 ng/mL for both analytes. Precision in relative standard deviation was < 9.37% for mobocertinib and < 12.03% for desmethyl-mobocertinib. Accuracy in relative error was within -7.23% to 9.18% for mobocertinib and -2.78% to 9.87% for desmethyl-mobocertinib. Extraction recovery was > 80% for both analytes. The validated LC-MS/MS method was successfully applied to the pharmacokinetic study of mobocertinib and desmethyl-mobocertinib in healthy human volunteers with K₂EDTA as anticoagulant after a single dose of mobocertinib (160 mg).