Axitirome

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.

CGS 26214 is a racemic compound having cholesterol-lowering activity in rats, dogs, and monkeys. This compound has two equipotent chiral components CGS 28934(-) and CGS 28935(+). An analytical challenge was to develop a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the analysis of the chiral components in human plasma following clinical doses of 1 mg or less. Several issues had to be addressed in order to devise a LC/MS/MS assay for the above compounds. First, the compounds were esters and susceptible to hydrolysis under experimental conditions. Second, a lower limit of quantitation (LLOQ) of 0.4 ng/ml was needed. Third, positive electrospray ionization of CGS 26214 did not yield sufficient sensitivity needed for the studies in humans. Consequently, LC/MS/MS conditions were optimized for negative ion mode of detection. Fourth, sample preparation steps proved to be critical in order to reduce the possibility of microbore chiral-HPLC column (100 x 1.0 mm i.d.) obstruction, chromatographic deterioration, and matrix mediated electrospray ion suppression. Although the present method addressed the above challenges, its major drawback was limited sample throughput capability. Nonetheless, the method was successfully applied to generate plasma concentration-time profiles for human subjects after oral doses (0.9 mg) of the racemate as well as the optically pure isomers.