Liquid chromatographic-tandem mass spectrometric assay for the simultaneous quantification of Camptosar® and its metabolite SN-38 in mouse plasma and tissues

A simple, rapid and sensitive LC-MS/MS bioanalytical method has been developed to simultaneously quantify Camptosar (CPT-11) and its active metabolite. SN-38, in mouse plasma and tissues. A single step protein precipitation with acetonitrile in 96-well plates was used for sample preparation. Camptothecin (CPT) was used as the internal standard. Fast separation of SN-38, CPT-11 and CPT was carried out isocratically on a C-18, 2 mm x 50 mm, 5 mu m HPLC column with a mobile phase containing acetonitrile and 20mM ammonium acetate (pH 3.5) and a 2.5 min chromatographic run time. The API 4000 MS/MS system was operated in positive ionization multiple reaction monitoring mode, and the transitions for SN-38, CPT-11 and CPT were 393.4 -> 349.3, 587.6 -> 167.2 and 349.3 -> 305.3, respectively. The SN-38 and CPT-11 concentrations in samples were calculated from a standard curve of peak area ratios of the analyte to that of the internal standard using a 1/x(2) weighted linear regression. The quantitation limit of 0.5 ng/mL was achieved by using a low sample volume (100 mu L) of plasma or tissue homogenates. The assay was linear over the concentration range of 0.5-500 ng/mL with acceptable precision and accuracy. The method was used for the quantification of CPT-11 and SN-38 in plasma and tissues to support a preclinical pharmacokinetics and tissue distribution study of CPT-11 in mice. (c) 2004 Elsevier B.V. All fights reserved.