Characterisation and identification of the human N+-glucuronide metabolite of cediranib

Pharmacokinetic Interaction of Rifampicin with Oral Versus Intravenous Anticancer Drugs: Challenges, Dilemmas and Paradoxical Effects Due to Multiple Mechanisms

Since many drugs are cytochrome P450 (CYP)-3A4 substrates, it has become common practice to assess drug-drug interaction (DDI) potential with a CYP3A4 inhibitor (ketoconazole) or inducer (rifampicin) in early drug development. Such an evaluation is relevant to anticancer drugs with metabolism governed by CYP3A4. DDIs with rifampicin are complex, involving other physiological mechanisms that may impact overall pharmacokinetics. Our objective was to study and delineate such mechanisms for oral versus intravenous anticancer drugs. We hypothesized that DDIs between anticancer drugs and rifampicin were primarily driven by CYP3A4 induction. This hypothesis was proven for the oral anticancer drugs; however, in some cases, other intrinsic mechanisms such as P-glycoprotein (Pgp)/UDP glucuronosyl transferase (UGT) induction and transporter inhibition may have played an important role alongside the induced CYP3A4 enzymes. The hypothesis that CYP3A4 induction would decrease drug exposure appeared paradoxical for intravenous romidepsin and-to a somewhat lesser extent-for cabazitaxel. In light of this dilemma in the interpretation of the pharmacokinetic data with rifampicin, several questions require further consideration. Given the complexity and paradoxical effects arising with DDIs with rifampicin, the continued preference for rifampicin as CYP3A4 inducer needs immediate re-appraisal.

In vitro pharmacokinetic profile of a benzopyridooxathiazepine derivative using rat microsomes and hepatocytes: identification of phases I and II metabolites

In the present study, the in vitro metabolic behavior of a benzopyridooxathiazepine (BZN), a potent tubulin polymerization inhibitor, was investigated by liquid chromatography-UV detection (LC-UV). First, simple and fast LC-UV methods have been optimized and validated to evaluate the pharmacokinetic profile of BZN using rat liver microsomes or hepatocytes primary cultures suspensions. Whatever the medium investigated, baseline resolution between the internal standard and BZN was achieved in a run time less than 15min using a Symmetry ODS column (150mm×4.6mm i.d., 5μm) and a mobile phase consisting of acetonitrile/water/formic acid 60:40:0.1 (v/v/v). Linearity was assessed in the 0.1-50μM and in the 0.05-5μM concentration ranges, respectively, in microsomal and hepatocyte matrix. According to the novel strategy based on the build of the accuracy profile, total error of the developed methods was included within the ±10% limits of acceptance. Then, from incubation of BZN with both liver microsomes and or hepatocytes, structural informations on phase I and phase II metabolites were acquired using liquid chromatography coupled to electrospray orbitrap mass spectrometer (LC-MS). Mass spectrum, double bond equivalent and elemental composition were useful data to access to the chemical structure of each metabolite. In microsomal suspension, four main metabolites were observed including monohydroxylation and dihydroxylation of the benzopyridooxathiazepine core, demethylation of the methoxyphenyl moiety, as well as their combinations. The phase II metabolites detected in hepatocytes suspension were the glucuronide adducts of both demethylated BZN and mono-oxygenated BZN. Based on the structural elucidation of the metabolites detected, we proposed an in vitro metabolic pathway of BZN, a new tubulin polymerization inhibitor.

Determination of cediranib in mouse plasma and brain tissue using high-performance liquid chromatography-mass spectrometry

A new high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) assay for cediranib, a tyrosine kinase inhibitor for VEGFRs, was developed and validated, for the determination of plasma and brain levels of cediranib in small specimen volumes. Tyrphostin (AG1478) was used as internal standard. Mouse plasma and brain homogenate samples were prepared using liquid-liquid extraction. The assay was validated for a 2.5-2500 ng/mL concentration range for plasma, and for 1-2000 ng/mL range for brain homogenate. For these calibration ranges, within-assay variabilities were 1.1-14.3% for plasma and 1.5-9.4% for brain homogenate; between-assay variabilities were 2.4-9.2% for plasma, and 4.9-10.2% for brain homogenate. Overall accuracy ranged from 101.5 to 107.0% for plasma and 96.5 to 100.2% for brain homogenate, for all target concentrations. The developed assay has been successfully applied for a brain distribution study in mice at an oral dose of 5 mg/kg.