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 microg 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 x 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.