Paleoecological insights from fossil freshwater mollusks of the Kanapoi Formation (Omo-Turkana Basin, Kenya)

International audienc

A dried blood spot assay for paclitaxel and its metabolites

After being used for decades in clinical screening, dried blood spots (DBS) have recently received considerable attention for their application in pharmacokinetic and toxicokinetic studies in rodents. The goal of this study was to develop and apply a DBS-based assay for a pharmacokinetic study of paclitaxel (PTX) and its metabolites in SCID/Beige mice. A fast and sensitive UHPLC-MS/MS method has been developed for the simultaneous determination of PTX, its three metabolites (6 alpha-hydroxy-paclitaxel, 3'-p-hydroxypacli taxel, and 6a,3'-p-dihydroxy-paclitaxel) and its stereoisomer 7-epi-p aclitaxel. The 10 mu L DBS sample was extracted with methanol for 20 min at 37 degrees C. After dilution of the extracts with water in a ratio of 1:1, the analytes were separated on a reversed-phase 2.1 mm I.D. column using gradient elution. The total run time was 2.5 min. The analytes were detected by use of multiple reaction monitoring mass spectrometry. The extraction recoveries of the compounds were all greater than 60%, resulting in a quantification limit of 1 ng/ml. The calibration curves ranged from 1 to 1000 ng/ml. The intra-day and inter-day imprecision (%CV) across three validation runs over four quality control levels were less than or equal to 14.6%. The accuracy was within +/-11.9% in terms of relative error. The described method is advantageous in terms of its ease-of-use and speed compared to other published PTX assays. The method's usefulness was demonstrated by applying it to a preclinical pharmacokinetic investigation of PTX and its metabolites in SCID/Beige mice with an intraperitoneal administration of 50 mg/kg Abraxane (R)

Characterization of porcine hepatic and intestinal drug metabolizing CYP450 : comparison with human orthologues from a quantitative, activity and selectivity perspective

Over the past two decades, the pig has gained attention as a potential model for human drug metabolism. Cytochrome P450 enzymes (CYP450), a superfamily of biotransformation enzymes, are pivotal in drug metabolism. Porcine CYP450 has been demonstrated to convert typical substrates of human CYP450. Nevertheless, knowledge and insight into porcine CYP450 quantity and substrate selectivity is scant, especially regarding intestinal CYP450. The current study aimed to map the quantities of hepatic and intestinal CYP450 in the conventional pig by using a proteomic approach. Moreover, the selectivity of the six most common used probe substrates (phenacetin, coumarin, midazolam, tolbutamide, dextromethorphan, and chlorzoxazone) for drug metabolizing enzyme subfamilies (CYP1A, CYP2A, CYP3A, CYP2C, CYP2D and CYP2E respectively), was investigated. Hepatic relative quantities were 4% (CYP1A), 31% (CYP2A), 14% (CYP3A), 10% (CYP2C), 28% (CYP2D) and 13% (CYP2E), whereas for the intestine only duodenal CYP450 could be determined with 88% for CYP3A and 12% for CYP2C. Furthermore, the results indicate that coumarin (CYP2A), midazolam (CYP3A), tolbutamide (CYP2C), and dextromethorphan (CYP2D) are as selective for porcine as for human CYP450. However, phenacetin (CYP1A2) and chlorzoxazone (CYP2E1) are less selective for the specific enzyme, despite similarities in selectivity towards the different enzymes involved compared to humans

The Other Press, February 1, 1984

Cisplatin is a first-line chemotherapeutic for the treatment of a wide variety of cancers since its discovery in the 1960s. Although various techniques have been reported for the measurement of total platinum in biological matrices, such as inductively coupled plasma-mass spectrometry and derivatization procedures, a specific, sensitive and robust assay for the quantification of intact cisplatin is still lacking. Therefore, we present a rapid, selective, sensitive, and reliable UHPLC-MS/MS based method for the determination of intact cisplatin in human plasma in support of a Phase II clinical trial. The optimal chromatographic behavior of cisplatin was achieved on a Syncronis HILIC column (50 x 2.1 mm, 1.7 mu m, zwitterionic stationary phase). The retention behavior of cisplatin on this zwitterion-based stationary phase was well described by an adsorptive interaction model. A simple sample preparation based on protein precipitation combined with the removal of phospholipids by HybridSPE-precipitation was developed. The method was proven to be free of a relative matrix effect. The assay was validated within a range of 20 - 10,000 ng/mL using 100 mu L of plasma sample. The intra and inter day precisions were all less than 7.6%, and none of the bias was greater than 13.1%, thus corroborating that the developed method is precise and accurate. As a proof of concept, the assay has been successfully applied to plasma samples obtained from different patients who were enrolled in the Phase II trial and were treated with cisplatin