Physiologically Based Pharmacokinetic Modelling of Cytochrome P450 2C9-Related Tolbutamide Drug Interactions with Sulfaphenazole and Tasisulam.

Background And Objectives: Cytochrome P450 2C9 (CYP2C9) is involved in the biotransformation of many commonly used drugs, and significant drug interactions have been reported for CYP2C9 substrates. Previously published physiologically based pharmacokinetic (PBPK) models of tolbutamide are based on an assumption that its metabolic clearance is exclusively through CYP2C9; however, many studies indicate that CYP2C9 metabolism is only responsible for 80-90% of the total clearance. Therefore, these models are not useful for predicting the magnitude of CYP2C9 drug-drug interactions (DDIs).

Industry Perspective on Contemporary Protein-Binding Methodologies: Considerations for Regulatory Drug-Drug Interaction and Related Guidelines on Highly Bound Drugs.

Regulatory agencies have recently issued drug-drug interaction guidelines, which require determination of plasma protein binding (PPB). To err on the conservative side, the agencies recommend that a 0.01 lower limit of fraction unbound (f) be used for highly bound compounds (>99%), irrespective of the actual measured values.

Comparison between Radioanalysis and F Nuclear Magnetic Resonance Spectroscopy in the Determination of Mass Balance, Metabolism, and Distribution of Pefloxacin.

Mass balance and metabolism studies using radiolabeled substances are well recognized as an important part of the drug development process. In this study, we directly assessed the use of fluorine nuclear magnetic resonance (F NMR) to achieve quantitative mass balance, metabolism, and distribution information for fluorinated compounds, without the need for radiolabeled synthesis or study. As a test case, the disposition of pefloxacin, a fluoroquinolone antibiotic, was evaluated in rats using quantitative F NMR in parallel with a radiolabeled study.

Using dried blood spot sampling to improve data quality and reduce animal use in mouse pharmacokinetic studies.

Traditional pharmacokinetic analysis in nonclinical studies is based on the concentration of a test compound in plasma and requires approximately 100 to 200 μL blood collected per time point. However, the total blood volume of mice limits the number of samples that can be collected from an individual animal-often to a single collection per mouse-thus necessitating dosing multiple mice to generate a pharmacokinetic profile in a sparse-sampling design. Compared with traditional methods, dried blood spot (DBS) analysis requires smaller volumes of blood (15 to 20 μL), thus supporting serial blood sampling and the generation of a complete pharmacokinetic profile from a single mouse.

Characterization of the expression and activity of carboxylesterases 1 and 2 from the beagle dog, cynomolgus monkey, and human.

The carboxylesterases (CESs) are a family of serine hydrolases that hydrolyze compounds containing an ester, amide, or thioester. In humans, two dominant forms, CES1 and CES2, are highly expressed in organs of first-pass metabolism and play an important role in xenobiotic metabolism. The current study was conducted to better understand species-related differences in substrate selectivity and tissue expression of these enzymes.

Dried blood spot sampling: coupling bioanalytical feasibility, blood-plasma partitioning and transferability to in vivo preclinical studies.

Background: The adoption of dried blood spot (DBS) sampling and analysis to support drug discovery and development requires the understanding of its bioanalytical feasibility as well as the distribution of the analyte in blood.

Results: Demonstrated the feasibility of adopting DBS for four test analytes representing diverse physico-chemical as well as pharmacokinetic parameters. The key findings include the use of a single extraction procedure across all four analytes, assay range of 1 to 5000 ng/ml, stability in whole blood as well as on-card, and the non-impact of blood volume.

Effect of gastric pH on the pharmacokinetics of a BCS class II compound in dogs: utilization of an artificial stomach and duodenum dissolution model and GastroPlus,™ simulations to predict absorption.

Dogs are one of the most commonly used non-rodent species in toxicology studies and are known to have basal stomach pH ranging from 2 to 7 in the fasted state. Thus absorption and resulting plasma exposure of weakly basic compounds administered as crystalline suspensions to dogs are often variable. LY2157299 is a potent and selective transforming growth factor (TGF)-beta receptor type 1 kinase (TGF-βRI) inhibitor that displayed variable absorption in early dog studies.

Recommended nomenclature for five mammalian carboxylesterase gene families: human, mouse, and rat genes and proteins.

Mammalian carboxylesterase (CES or Ces) genes encode enzymes that participate in xenobiotic, drug, and lipid metabolism in the body and are members of at least five gene families. Tandem duplications have added more genes for some families, particularly for mouse and rat genomes, which has caused confusion in naming rodent Ces genes. This article describes a new nomenclature system for human, mouse, and rat carboxylesterase genes that identifies homolog gene families and allocates a unique name for each gene.

Genomic analysis of the carboxylesterases: identification and classification of novel forms.

Large species differences in the expression of carboxylesterases (CE) have been described, but the interrelationships of CEs across species are not well characterized. In the current analyses, sequences with genomic structures similar to human CEs were found in piscine, avian, and mammalian genomes. Analyses of these genes suggest that four CE groups existed prior to mammalian divergence, with another form occurring after eutherian-marsupial divergence, yielding five distinct mammalian CE groups.

Synthesis, crystallization, and biological evaluation of an orally active prodrug of gemcitabine.

The design, synthesis, and biological characterization of an orally active prodrug (3) of gemcitabine are described. Additionally, the identification of a novel co-crystal solid form of the compound is presented. Valproate amide 3 is orally bioavailable and releases gemcitabine into the systemic circulation after passing through the intestinal mucosa.

The intestinal absorption of a prodrug of the mGlu2/3 receptor agonist LY354740 is mediated by PEPT1: in situ rat intestinal perfusion studies.

LY354740 is a potent mGlu2/3 agonist with a limited oral bioavailability. Its alanyl prodrug, LY544344, showed high affinity to the intestinal peptide transporter PEPT1, and improved the oral bioavailability of LY354740 in various animal models. The aim of the present study was to investigate the mechanism of in vivo absorption of the dipeptidic prodrug LY544344.

Transepithelial transport of the group II metabotropic glutamate 2/3 receptor agonist (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate (LY354740) and its prodrug (1S,2S,5R,6S)-2-[(2'S)-(2'-amino)propionyl]aminobicyclo[3.1.0]hexane-2,6-dicarboxylate (LY544344).

The limited oral bioavailability of the potent and selective group II metabotropic glutamate (mGlu) 2/3 receptor agonist, (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate (LY354740), was shown to be improved by its peptidyl prodrug, (1S,2S,5R,6S)-2-[(2'S)-(2'-amino)propionyl]aminobicyclo[3.

The biotransformation of prasugrel, a new thienopyridine prodrug, by the human carboxylesterases 1 and 2.

2-Acetoxy-5-(alpha-cyclopropylcarbonyl-2-fluorobenzyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine (prasugrel) is a novel thienopyridine prodrug with demonstrated inhibition of platelet aggregation and activation. The biotransformation of prasugrel to its active metabolite, 2-[1-[2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl]-4-mercapto-3-piperidinylidene]acetic acid (R-138727), requires ester bond hydrolysis, forming the thiolactone 2-[2-oxo-6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl]-1-cyclopropyl-2-(2-fluorophenyl)ethanone(R-95913), followed by cytochrome P450-mediated metabolism to the active metabolite. The presumed role of the human liver- and intestinal-dominant carboxylesterases, hCE1 and hCE2, respectively, in the conversion of prasugrel to R-95913 was determined using expressed and purified enzymes.

Effect of buffer components and carrier solvents on in vitro activity of recombinant human carboxylesterases.

Introduction: The effects of buffer and substrate solvent conditions on in vitro activity of carboxylesterases (CE) have not been previously described. Therefore, it is unknown if the many different assay conditions used by various laboratories have a substantial impact on the activity of CE enzymes.

Methods: Three human CEs were expressed and purified, and the hydrolysis of 4-nitrophenyl butyrate was measured to assess enzyme activity.

Pharmacokinetics, metabolism, and excretion of the intestinal peptide transporter 1 (SLC15A1)-targeted prodrug (1S,2S,5R,6S)-2-[(2'S)-(2-amino)propionyl]aminobicyclo[3.1.0.]hexen-2,6-dicarboxylic acid (LY544344) in rats and dogs: assessment of first-pass bioactivation and dose linearity.

The peptidyl prodrug (1S,2S,5R,6S)-2-[(2'S)-(2-Amino)propionyl]a-minobicyclo[3.1.0.

Improved bioavailability of the mGlu2/3 receptor agonist LY354740 using a prodrug strategy: in vivo pharmacology of LY544344.

Numerous studies have indicated that selective agonists of group II metabotropic glutamate (mGlu) receptors, such as LY354740 [(1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate] and LY379268 [(-)-2-oxa-4-aminobicyclo[3.