Study On The Pharmacokinetics And Tissue Distribution Of CPT13, A Novel Camptothecin Analog

In an attempt to improve water solubility, decrease the antitumor activity and increase stability in blood of CPT, a series of 10-subsituted nitrous heterocyclic CPT analogues were prepared by facile nucleophic substitution. Based on our previous experiment, we found that CPT 13 was best effective. Preliminary study evaluating its anti-tumor in vitro, it was revealed that CPT13 exhibited good topoisomerase I inhibitory activity, which is one of the mechanism of action of CPT13, it can also inhibit PC3, HCT8, A549 and MCF7 in the range 0.008 to 2.5μM obvious time-and dose-dependent, and meantime it possessed higher in vitro cytoxicity activity towards human colon cancer HCT8 cell line. In order to further explore the underlying mechanism of cell growth inhibition of CPT13 towards HCT8 cell line, our previous report had shown that CPT13 also studied apoptosis induced HCT8 the molecular mechanisms that CPT 13 induced apoptosis pathway and the regulation of he expression of some related apoptotic proteins such as Bcl-2,Bax and p53 protein levels. In this study, the pharmacokinetics and tissue distribution of camptothecin derivatives CPT 13 were further reported by using high-performance liquid chromatography (HPLC) and liquid chromatography tandem mass spectrometry (LC-MS/MS). The results were as follows:1. In this study, reversed-phase high performance liquid chromatographic (HPLC) method using tandem mass spectrometry detection was initially developed and validated for the analysis of 10-(2-pyrazolyl-ethoxy)-(20S)-camptothecin (CPT13) in rat plasma. Detection was performed using a triple quadrupole tandem mass spectrometer in multiple reactions monitoring (MRM) mode via an electrospray ionization (ESI) source. The calibration curve was linear (r(?)=0.9998) over the concentration range of 1-1000 ng/mL, with a LLOQ of lng/mL for CPT13. The inter-and intra-day precisions (%R.S.D.) were less than 2.58% and 6.28% , respectively, and the accuracies (%) were within the range of 97.34-110.67%. CPT13 in rat plasma was stable in different storage conditions.2. The pharmacokinetics results showed that after oral administration of different doses (50 mg/kg,30 mg/kg and 10 mg/kg) of CPT13, the higher doses resulted in higher values for AUC0-t and AUC0-∞. The results also showed that the t1/2 of intravenous CPT13 was approximately 0.67 h. The proposed method could determine CPT13 concentrations until 480min after administration. The results also showed that CPT13 undergoes extensive and rapid first-pass metabolism after intravenous administration. After 2 h, the concentration of CPT 13 in plasma blood was difficult to detect and the concentration was up to LLOQ. The pharmacokinetic parameters of the drug, as determined from different doses (oral and intravenous), produced an estimated absolute oral bioavailability (F) of～0.3% .3. At the same time, HPLC assay was established for estimating the CPT13 concentration in various tissues after intravenous administration in mice. The specificity, linearity, sensitivity, accuracy, precision, recovery and stability were good. After intravenous administration, the highest concentration weres found in the lung, liver and kidney, followed by the spleen and heart, the least in the stomach and small intestine. After 5 min administration, the concentration of CPT13 was detected but the concentration was up to LLOQ in the stomach, but at the following times the concentration were not detected. The lowest concentration were founded in mall intestine, heart and spleen after 60min administration, but it were still detected in lung, liver and kidney after 480min. Calculated the AUC of CPT13 in different tissues, it can be seen clearly the AUC of the lung, liver and kidney were more greater than other tissues.In summary, through animal experiments, the pharmacokinetic parameters were investigated after a series of oral and intravenous administration. CPT13 concentration was studied in different tissues afer intravenous administration.The resulting information about CPT13 will provide the basis for clinical trials.