Quantitative determination of CGS 26214, a cholesterol lowering agent, in human plasma using negative electrospray ionization liquid chromatography–tandem mass spectrometry

CGS 26214 is a synthetic cholesterol-lowering agent shown to be active in the rat, dog and monkey. The present work was conducted to develop a sensitive liquid chromatography–tandem mass spectrometry (LC–MS–MS) method for quantitative determination of the compound in human plasma following clinical doses of 10–100 μg per day. A number of analytical challenges were encountered during the development of the assay. The compound was an ester and susceptible to hydrolysis under experimental conditions. A lower limit of quantitation of 50 pg/ml was needed due to the low clinical doses. Positive electrospray ionization of CGS 26214 yielded insufficient sensitivity needed for the studies. Consequently, LC–MS–MS conditions were optimized for the negative ion mode of detection. The sample preparation steps proved to be critical in order to reduce the possibility of microbore column (50 mm×1.0 mm I.D.) obstruction, chromatographic deterioration, and matrix mediated electrospray ion suppression. The present method addressed the above issues. The method was accurate and reproducible and was successfully applied to generate plasma concentration–time profiles for human subjects after low oral doses of the compound.