Association of pharmacokinetic profiles of lenalidomide in human plasma simulated using pharmacokinetic data in humanized-liver mice with liver toxicity detected by human serum albumin RNA

Species Specificity and Selection of Models for Drug Oxidations Mediated by Polymorphic Human Enzymes

Many drug oxygenations are mainly mediated by polymorphic cytochromes P450 (P450s) and also by flavin-containing monooxygenases (FMOs). More than 50 years of research on P450/FMO-mediated drug oxygenations have clarified their catalytic roles. The natural product coumarin causes hepatotoxicity in rats via the reactive coumarin 3,4-epoxide, a reaction catalyzed by P450 1A2; however, coumarin undergoes rapid 7-hydroxylation by polymorphic P450 2A6 in humans. The primary oxidation product of the teratogen thalidomide in rats is deactivated 5'-hydroxythalidomide plus sulfate and glucuronide conjugates; however, similar 5'-hydroxythalidomide and 5-hydroxythalidomide are formed in rabbits in vivo. Thalidomide causes human P450 3A enzyme induction in liver (and placenta) and is also activated in vitro and in vivo by P450 3A through the primary human metabolite 5-hydroxythalidomide (leading to conjugation with glutathione/nonspecific proteins). Species differences exist in terms of drug metabolism in rodents and humans, and such differences can be very important when determining the contributions of individual enzymes. The approaches used for investigating the roles of human P450 and FMO enzymes in understanding drug oxidations and clinical therapy have not yet reached maturity and still require further development. SIGNIFICANCE STATEMENT: Drug oxidations in animals and humans mediated by P450s and FMOs are important for understanding the pharmacological properties of drugs, such as the species-dependent teratogenicity of the reactive metabolites of thalidomide and the metabolism of food-derived odorous trimethylamine to non-odorous (but proatherogenic) trimethylamine N-oxide. Recognized differences exist in terms of drug metabolism between rodents, non-human primates, and humans, and such differences are important when determining individual liver enzyme contributions with substrates in in vitro and in vivo systems.

Low cerebrospinal fluid-to-plasma ratios of orally administered lenalidomide mediated by its low cell membrane permeability in patients with hematologic malignancies

Lenalidomide is a synthetic analog of thalidomide formed by the removal of one keto group (plus the addition of an amino group); it has anti-tumor activities beneficial for the treatment of hematologic malignancies. However, lenalidomide distribution to brain in animal models is reportedly low compared with that of thalidomide. The aim of this study was to evaluate plasma and cerebrospinal fluid concentrations of lenalidomide in three patients with malignant hematologic malignancies. Lenalidomide was detected in plasma from the three Japanese patients 1.5 h following oral administration of 20 mg lenalidomide using liquid chromatography/mass spectrometry, despite the in vitro gastrointestinal permeability of lenalidomide being low. Clinically observed cerebrospinal fluid-to-plasma ratios of lenalidomide were low (1.3-2.4%). Observed influx permeability values for lenalidomide in monkey blood-brain barrier model and human placental cell systems were one order of magnitude lower than those of thalidomide and another second-generation drug, pomalidomide along with a positive permeability control, caffeine. Because of the low cell-barrier permeability of lenalidomide demonstrated in in vitro assays, clinically relevant pharmacokinetic profiles of lenalidomide resulted in low penetrability from plasma into cerebrospinal fluid in patients with hematologic malignancies. Lenalidomide is conclusively suggested to expert its favorable immunomodulatory effects via systemic exposures in the patients.

Structure-Activity Relationship (SAR) Model for Predicting Teratogenic Risk of Antiseizure Medications in Pregnancy by Using Support Vector Machine

Teratogenicity is one of the main concerns in clinical medications of pregnant women. Prescription of antiseizure medications (ASMs) in women with epilepsy during pregnancy may cause teratogenic effects on the fetus. Although large scale epilepsy pregnancy registries played an important role in evaluating the teratogenic risk of ASMs, for most ASMs, especially the newly approved ones, the potential teratogenic risk cannot be effectively assessed due to the lack of evidence. In this study, the analyses are performed on any medication, with a focus on ASMs. We curated a list containing the drugs with potential teratogenicity based on the US Food and Drug Administration (FDA)-approved drug labeling, and established a support vector machine (SVM) model for detecting drugs with high teratogenic risk. The model was validated by using the post-marketing surveillance data from US FDA Spontaneous Adverse Events Reporting System (FAERS) and applied to the prediction of potential teratogenic risk of ASMs. Our results showed that our proposed model outperformed the state-of-art approaches, including logistic regression (LR), random forest (RF) and extreme gradient boosting (XGBoost), when detecting the high teratogenic risk of drugs (MCC and recall rate were 0.312 and 0.851, respectively). Among 196 drugs with teratogenic potential reported by FAERS, 136 (69.4%) drugs were correctly predicted. For the eight commonly used ASMs, 4 of them were predicted as high teratogenic risk drugs, including topiramate, phenobarbital, valproate and phenytoin (predicted probabilities of teratogenic risk were 0.69, 0.60 0.59, and 0.56, respectively), which were consistent with the statement in FDA-approved drug labeling and the high reported prevalence of teratogenicity in epilepsy pregnancy registries. In addition, the structural alerts in ASMs that related to the genotoxic carcinogenicity and mutagenicity, idiosyncratic adverse reaction, potential electrophilic agents and endocrine disruption were identified and discussed. Our findings can be a good complementary for the teratogenic risk assessment in drug development and facilitate the determination of pharmacological therapies during pregnancy.

Hepatotoxicological potential of P-toluic acid in humanised-liver mice investigated using simplified physiologically based pharmacokinetic models

p-Toluic acid, a metabolite of organic solvent xylene, has a high reported no-observed-effect level (NOEL, 1000 mg/kg) in rats, possibly because of direct glycine conjugation to methylhippuric acid. In this study, plasma levels of p-toluic acid and its glycine conjugate in mice and humanised-liver mice were evaluated after oral administrations.Although rapid conversion of p-toluic acid to its glycine conjugate was evident from mouse plasma concentrations, the biotransformation of p-toluic acid was slower in humanised-liver mice. The input parameters for physiologically based pharmacokinetic (PBPK) models were determined using fitting procedures to create PBPK-generated plasma concentration curves.The PBPK-modelled hepatic concentrations of p-toluic acid in humanised-liver mice were higher than those observed in plasma. PBPK-modelled hepatic and plasma concentrations of p-toluic acid also indicated slow elimination in humans.These results suggest that rapid conjugations of p-toluic acid reportedly observed in rats could result in overestimation of NOELs for conjugatable chemicals when extrapolated to humanised-liver mice or humans.

Pharmacokinetics of primary oxidative metabolites of thalidomide in rats and in chimeric mice humanized with different human hepatocytes

The approved drug thalidomide is teratogenic in humans, nonhuman primates, and rabbits but not in rodents. The extensive biotransformation of 5'-hydroxythalidomide after oral administration of thalidomide (250 mg/kg) in rats was investigated in detail using liquid chromatography-tandem mass spectrometry. Probable metabolites 5'-hydroxythalidomide sulfate and glucuronide were extensively formed, with approximately tenfold and onefold peak areas, respectively, to the primary 5'-hydroxythalidomide measured using authentic standards. As a minor metabolite, 5-hydroxythalidomide was also detected. The output of simplified physiologically based pharmacokinetic rat models was consistent with the observed in vivo data under a metabolic ratio of 0.05 for the hepatic intrinsic clearance of thalidomide to unconjugated 5'-hydroxythalidomide. The aggregate of unconjugated and sulfate/glucuronide conjugated 5'-hydroxythalidomide forms appear to be the predominant metabolites in rats. Two hours after oral administration of thalidomide (100 mg/kg) to chimeric mice humanized with four different batches of genotyped human hepatocytes, the plasma concentration ratios of 5-hydroxythalidomide to 5'-hydroxythalidomide were correlated with replacement indexes of human liver cells previously transplanted in immunodeficient mice. These results indicate that rodent livers mediate thalidomide primary oxidation, leading to extensive deactivation in vivo to unconjugated/conjugated 5'-hydroxythalidomide and suggest that thalidomide activation might be dependent on the humanized livers in mice transplanted with human hepatocytes.

Simple pharmacokinetic models accounting for drug monitoring results of atomoxetine and its 4-hydroxylated metabolites in Japanese pediatric patients genotyped for cytochrome P450 2D6

Atomoxetine is an approved medicine for attention-deficit/hyperactivity disorder and a cytochrome P450 2D6 (CYP2D6) probe substrate. Simple physiologically based pharmacokinetic (PBPK) models and compartment models were set up to account for drug monitoring results of 33 Japanese patients (6-15 years of age) to help establish the correct dosage for the evaluation of clinical outcomes. The steady-state one-point drug monitoring data for the most participants indicated the extensive biotransformation of atomoxetine to 4-hydroxyatomoxetine under individually prescribed doses of atomoxetine. However, 5 participants (with impaired CYP2D6 activity scores based on the CYP2D6 genotypes) showed high plasma concentrations of atomoxetine (0.53-1.5 μM) compared with those of total 4-hydroxyatomoxetine (0.49-1.4 μM). Results from full PBPK models using the in-built Japanese pediatric system of software Simcyp, one-compartment models, and new simple PBPK models (using parameters that reflected the subjects' small body size and normal/reduced CYP2D6-dependent clearance) could overlay one-point measured drug/metabolite plasma concentrations from almost common 28 participants within threefold ranges. Validated one-compartment or simple PBPK models can be used to predict steady-state plasma concentrations of atomoxetine and/or its primary metabolites in Japanese pediatric patients (>6 years) who took a variety of individualized doses in a clinical setting.

Pharmacokinetics of anticoagulants apixaban, dabigatran, edoxaban and rivaroxaban in elderly Japanese patients with atrial fibrillation treated in one general hospital

Steady-state plasma concentrations of anticoagulants and the time since the previous administration in mainly outpatients with atrial fibrillation administered standard or reduced doses were analyzed for 110 elderly Japanese subjects (mean age, 76 years) treated with apixaban (2.5 or 5.0 mg twice daily), dabigatran etexilate (110 or 150 mg twice daily), edoxaban (30 or 60 mg once daily) or rivaroxaban (10 or 15 mg once daily) at one general hospital. The pharmacokinetics in patients treated with standard and reduced doses of the four anticoagulants using liquid chromatography-tandem mass spectrometry was compared with the concentration ranges estimated using physiologically based pharmacokinetic modeling. Reduced doses of anticoagulants resulted in relatively small pharmacokinetic variations compared with the standard dose. Statistical analyses revealed that renal impairment is likely not the sole determinant factor for high plasma concentrations of apixaban, dabigatran, edoxaban and rivaroxaban. Patients with atrial fibrillation should be treated with the correct doses of oral anticoagulants as specified in the package inserts (e.g. reduced doses for elderly patients, patients with low body weights and in combination with P-glycoprotein inhibitor drugs) to avoid excessive or insufficient doses of direct oral anticoagulants.