A high-performance liquid chromatography method using ultraviolet detection for the quantitation of flavopiridol from human plasma

Flavopiridol is an inhibitor of cyclin-dependent kinase, a key regulator of cell cycle, and is currently under clinical trials. We developed and validated an HPLC assay method for the quantitation of flavopiridol in human plasma samples. The sample preparation consisted of protein precipitation with acetonitrile. Separation was accomplished on a C(18) column and a C(18) precolumn insert utilizing a gradient profile consisting of ammonium acetate and methanol. Ultraviolet detection was set at 268 nm for flavopiridol and 323 nm for umbelliferone, the internal standard. The method was validated over flavopiridol concentration range of 0.025-3.0 microg/mL using 250 microL of plasma. The assay was linear over this concentration range with a coefficient of variation less than 10% for inter- and intra-assay. The retention times were around 6.2 min for umbelliferone and 9.8 min for flavopiridol. The recoveries of flavopiridol and umbelliferone were 88.6 +/- 1.0% and 97.1 +/- 3.7%, respectively. This method is suitable for quantifying flavopiridol in plasma samples and further characterizing the clinical pharmacology of this compound.