Validation study of assay method for DX-8951 and its metabolite in human plasma and urine by high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry

A new liquid chromatographic/mass spectrometric assay has been developed for the determination of DX-8951, a new anti-tumor drug, and its 4-hydroxymethyl metabolite (UM-1) in human plasma and urine. Solid-phase extractions were used for sample preparation. A gradient reverse-phase HPLC separation was developed with mobile phases consisting of trifluoroacetic acid and methanol. The detection was conducted using atmospheric pressure chemical ionization tandem mass spectrometry in the selected reaction monitoring mode. A structural analog, camptothecin (CPT), was used as the internal standard. The assay was validated for the determination of DX-8951 and UM-1 in human plasma and urine. The lower limits of quantitation of DX-8951 and UM-1 were 0.1 ng/mL in plasma and 1 ng/mL in urine. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.