An ultra-sensitive liquid chromatography tandem mass spectrometry method for the simultaneous quantification of ²H₆-alectinib and alectinib in human plasma to support a microtracer food-effect trial

A liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the quantification of ²H₆-alectinib and alectinib was developed and validated for the support of a pilot microtracer food-effect trial. The aim of the bioanalytical method was the simultaneous quantification of low ²H₆-alectinib concentrations and high alectinib concentrations that are present in study samples, using a single sample pre-treatment and analysis method. Sample preparation consisted of liquid-liquid extraction with tert-butyl methyl ether (TBME). The final extract was injected on a C18 column (1.7 μm particles, 50 × 2.1 mm ID) with gradient elution. A triple quadruple mass spectrometer operating in positive method was used for detection and quantification. The validated concentration ranges were from 5 to 400 pg/mL for ²H₆-alectinib and from 25 to 2000 ng/mL for alectinib. The bias was within ±3.5 % and ± 5.1 % and precisions ≤5.7 % and ≤ 1.9 % for ²H₆-alectinib and alectinib, respectively. By correcting for the interference of natural abundant isotopes of alectinib, ²H₆-alectinib plasma concentrations between 1 and 5 pg/mL could be quantified, with bias was within ±15.9 % and precision ≤12.5 % in the presence of 400 ng/mL or 800 ng/mL alectinib. The clinical application was successfully applied to quantify ²H₆-alectinib and alectinib in plasma samples from a participant enrolled in a microtracer food-effect study.