Development of an optimized procedure for the preparation of rat intestinal microsomes: comparison of hepatic and intestinal microsomal cytochrome P450 enzyme activities in two rat strains.

The objective of this study was to characterize cytochrome P450 (CYP) activities in both intestinal and hepatic microsomes from Wistar and Sprague-Dawley rats. Specific probes for measuring CYP activities were selected using rat recombinant CYP. The intestinal microsome preparation was optimized getting a more relevant and reproducible abundance of CYPs to measure CYP activities. Testosterone, propranolol, diclofenac, and midazolam were determined as specific substrates of rat CYP2C11, CYP2D2, CYP2C6, and CYP3A, respectively. Ethoxyresorufin and pentoxyresorufin were not specific substrates of CYP1A2 and CYP2B1, respectively. Hepatic and intestinal microsomes expressed active CYP1A1, CYP1A2, CYP2B1, and CYP3A2. Only liver expressed active CYP2C6, CYP2C11, and CYP2D2. Wistar liver expressed more active CYP1A and CYP3A2, but less active CYP2B1 than Wistar intestine. Sprague-Dawley liver expressed more active CYP2B1 and CYP3A2, but less active CYP1A than Sprague-Dawley intestine. In conclusion, CYP activities were qualitatively equivalent but not quantitatively in both strains.

Physiologically Based Models in Regulatory Submissions: Output From the ABPI/MHRA Forum on Physiologically Based Modeling and Simulation.

Under the remit of the Ministerial Industry Strategy Group (MISG), the Association of the British Pharmaceutical Industry (ABPI) and Medicines and Healthcare products Regulatory Agency (MHRA) hosted a meeting to explore physiologically based pharmacokinetic modeling and simulation, focusing on the clinical component of regulatory applications. The meeting took place on 30 June 2014 with international representatives from industry, academia, and regulatory agencies. Discussion topics were selected to be complementary to those discussed at an earlier US Food and Drug Administration (FDA) meeting. This report summarizes the meeting outcomes, focusing on the European regulatory perspective.

Use of nonlinear mixed effect modeling for the meta-analysis of preclinical pharmacokinetic data: application to S 20342 in the rat.

The standard two-stage analysis of separate preclinical pharmacokinetic (PK) and toxicokinetic (TK) studies may lead to good information on the bioavailability in the rat at a low (pharmacologic) dose but only an idea on the dose/exposure relationship, on gender, and on time effect. In view of these drawbacks, we decided therefore to explore the usefulness of the implementation of a meta-analysis in preclinical studies in a given species (the rat in this case) taking as an example S 20342, an investigational new drug with potential antipsychotic properties. A nonlinear mixed-effect PK model was built from all intravenous (IV) and oral (PO) data collected until the completion of the 4-week toxicity study. The database included data from 201 Wistar rats (161 males and 40 females). Forty animals received the drug IV and 161 PO. The treatment duration ranged from 1 day to 4 weeks. IV doses were 3, 5, and 20 mg/kg, and 11 different oral doses were tested in the range of 5 to 200 mg/kg. Three different salts were administered PO: hydrochloride, sulfate, and mesylate. The modeling was performed with NONMEM IV. The best pharmacokinetic model was a two-compartment model with simultaneous first-order and zero-order absorption. The combination of these two input functions allowed the model to fit the peak plasma concentrations observed in the first hour (first order), especially after oral administration of low doses, and to take into account the prolonged absorption phase when the dose increased (zero order). A significant gender effect was found on CL. In addition, significant positive correlations were found between weight and CL, weight and Vc, and dose and the dose fraction after a zero-order absorption. No covariate significantly influenced the other parameters. In conclusion, the meta-analysis of preclinical data allowed for an objective assessment of statistically significant effects throughout the model-building process, leading to a better knowledge (and thus a better understanding) of preclinical PK in the rat. Moreover, the model obtained could be used to interpret further preclinical specific studies involving a sparse sampling design (e.g., further TK studies and PK/PD studies). Although this meta-analysis is more complicated than the noncompartmental approach and requires a case-by-case effort, it could be very useful to integrate this approach in the preclinical development process.

Pharmacokinetic predictions in children by using the physiologically based pharmacokinetic modelling.

Nowadays, 50-90% of drugs used in children have never been actually studied in this population. Consequently, either our children are often exposed to the risk of adverse drug events or to lack of efficacy, or they are unable to benefit from a number of therapeutic advances offered to adults, as no clinical study has been properly performed in children. Actually the main methods used to calculate the dose for a child are based on allometric methods taking into account different categories of age, the body weight and/or the body surface area. Unfortunately, these calculation methods consider the children as small adults, which is not the case. Physiologically based pharmacokinetics is one way to integrate the physiological changes occurring in the childhood and to anticipate their impact on the pharmacokinetic processes: absorption, distribution, metabolism and excretion/elimination. From different examples, the application of this modelling approach is discussed as a possible and valuable method to minimize the ethical and technical difficulties of conducting research in children.

S 12340: a potent inhibitor of the oxidative modification of low-density lipoprotein in vitro and ex vivo in WHHL rabbits.

Oxidative modification of low-density lipoprotein (LDL) is thought to play a key role in the formation of foam cells and in the initiation and progression of the atherosclerotic plaque. After evaluation of a large number of original drugs, S 12340 was found to be the most potent compound in inhibiting in a dose-dependent manner the human LDL oxidative modification induced either by copper ions or by cultured endothelial cells. Both the electrophoretic mobility and the thiobarbituric acid reactive substances returned to almost normal values in the presence of 0.5 microM of S 12340. Watanabe heritable hyperlipidemic rabbits were treated orally for 3 days or for 1 month with S 12340 to evaluate the potential protective effect of the compound on LDL oxidative modification induced ex vivo. Purified LDL from placebo and treated rabbits were submitted to oxidation, and S 12340 was effectively able to protect LDL in a dose-dependent manner and at doses as low as 10 mg/kg/day. Purified LDL from animals sacrificed at various times after oral administration of S 12340 were protected against oxidation for at least 6 h after the last administration of the compound. These findings are in good agreement with the plasma and LDL levels of S 12340 in these WHHL rabbits. S 12340, probucol and vitamin E were all able to decrease the optical density of the 1,1-diphenyl-2-picrylhydrazyl solution, demonstrating their free radical scavenging properties. The pharmacological properties of the compound suggest that S 12340 may be of potential interest for a new therapeutic approach to atherosclerosis.