SciCombinator

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Journal: Drug metabolism and pharmacokinetics

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 A pharmacokinetic/pharmacodynamic (PK/PD) analysis is important in antibiotic chemotherapy. Basically, the in vivo efficacy of antibiotics that exert concentration-dependent effects can be predicted using conventional PK/PD indices such as the ratio of the area under the curve to the minimum inhibitory concentration (AUC/MIC) and/or the ratio of the maximum plasma concentration to MIC (Cmax/MIC), whereas that of antibiotics with time-dependent effects can be determined using the period of time for which the drug concentration exceeds the MIC (time above MIC [TAM]). However, an optimal PK/PD index remains to be established for some antibiotics. Thus, a PK/PD model, which describes the PK profile and effect of an antibiotic, was developed, and the results obtained from this model were interpreted to form a PK/PD index map to assess the optimal PK/PD index for the antibiotic. The findings from the map were generally consistent with clinical outcomes even for the antibiotics which became the exception by the conventional classification. For example, AUC/MIC was an optimal index for azithromycin despite its time-dependent bactericidal activity, and Cmax/MIC was a poor index for arbekacin despite its concentration-dependent profile. Thus, the map would be useful for selecting the appropriate PK/PD index for an antibiotic.

Concepts: Time, Effectiveness, Ratio, Antibiotic, Unified Modeling Language, Erythromycin, Bactericide, Ruby

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This study aimed to evaluate the potential of α-cedrene as a new anti-obesity drug by characterizing absorption, metabolism and pharmacokinetics in rats. α-Cedrene was administered intravenously (10 and 20 mg/kg) and orally (50 and 100 mg/kg) to female and male Sprague-Dawley rats. Blood, tissues, urine, and feces were collected at predetermined times. α-Cedrene concentrations were determined by a validated gas chromatography-tandem mass spectrometry (GC-MS/MS). A gas chromatography-mass selective detection (GC-MSD) method was used to identify the major metabolite. After i.v. injection, α-cedrene exhibited a rapid clearance (98.4-120.3 ml/min/kg), a large distribution volume (35.9-56.5 l/kg), and a relatively long half-life (4.0-6.4 h). Upon oral administration, it was slowly absorbed (Tmax = 4.4 h) with bioavailability of 48.7-84.8%. No gender differences were found in its pharmacokinetics. Upon oral administration, α-cedrene was highly distributed to tissues, with the tissue-to-plasma partition coefficients (Kp) far greater than unity for all tissues. In particular, its distribution to lipid was notably high (Kp = 132.0) compared to other tissues. A mono-hydroxylated metabolite was identified as a preliminary metabolite in rat plasma. These results suggest that α-cedrene has the favorable pharmacokinetic characteristics to be further tested as an anti-obesity drug in clinical studies.

Concepts: Pharmacology, Male, Metabolism, Gender, Distribution, Absorption, Pharmacokinetics, Bioavailability

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Tralokinumab is a human monoclonal antibody in clinical development for asthma and atopic dermatitis that specifically neutralizes interleukin-13. This phase I, single-blind, randomized, placebo-controlled, single ascending-dose study assessed the safety, tolerability, pharmacokinetics (PK), and immunogenicity of subcutaneous tralokinumab (150, 300, or 600 mg) in thirty healthy Japanese adults. The most frequent treatment-emergent adverse event (TEAE) in all treatment groups was injection-site pain. The frequency and severity of TEAEs was similar across tralokinumab doses. Cmax, AUC(0-t), and AUC(0-inf) increased in a dose-proportional manner, and mean t1/2 ranged from 20 to 25 days. No anti-drug antibodies were detected. A post-hoc pooled population PK modeling analysis, incorporating PK data from this study, demonstrated that Japanese individuals had greater systemic exposure to tralokinumab than non-Japanese individuals. This difference was not clinically relevant and was primarily due to differences in body weight, with lower body weight associated with greater PK exposure. Japanese ethnicity was not a significant predictor of tralokinumab PK. This study indicates that single-dose subcutaneous administration of tralokinumab 150-600 mg was well tolerated in Japanese healthy volunteers, and supports the 300 mg dose selection for Japanese patients with asthma in ongoing clinical trials.

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Pharmacotherapy shows striking individual differences in pharmacokinetics and pharmacodynamics, involving drug efficacy and adverse reactions. Recent genetic research has revealed that genetic polymorphisms are important intrinsic factors for these inter-individual differences. This pharmacogenomic information could help develop safer and more effective precision pharmacotherapies and thus, regulatory guidance/guidelines were developed in this area, especially in the EU and US. The Project for the Promotion of Progressive Medicine, Medical Devices, and Regenerative Medicine by the Ministry of Health, Labour and Welfare, performed by Tohoku University, reported scientific information on the evaluation of genetic polymorphisms, mainly on drug metabolizing enzymes and transporters, during non-clinical studies and phase I clinical trials in Japanese subjects/patients. We anticipate that this paper will be helpful in drug development for the regulatory usage of pharmacogenomic information, most notably pharmacokinetics.

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This study describes the total disposition profiling of rosuvastatin (RSV) and pitavastatin (PTV) using a single systematic procedure called D-PREX (Disposition Profile Exploration) in sandwich-cultured human hepatocytes (SCHH). The biliary excretion fractions of both statins were clearly observed, which were significantly decreased dependent on the concentration of Ko143, an inhibitor for breast cancer resistance protein (BCRP). Ko143 also decreased the basolateral efflux fraction of RSV, whereas that of PTV was not significantly affected. To understand these phenomena, effects of Ko143 on biliary excretion (BCRP and multidrug resistance-associated protein (MRP) 2) and basolateral efflux (MRP3 and MRP4) transporters were examined using transporter-expressing membrane vesicles. BCRP, MRP3 and MRP4-mediated transport of RSV was observed, and Ko143 inhibited these transporters except MRP3. BCRP and MRP4 also mediated the transport of PTV, but the Ko143-mediated inhibition was only clear for BCRP. These results might explain the Ko143-mediated complete and partial inhibition of the biliary excretion and the basolateral efflux of RSV, respectively, in SCHH. In conclusion, D-PREX with sequential sampling of supernatants prior to cell lysis enables the evaluation of total drug disposition profiles resulting from complex interplays of intracellular pathways, which would provide high-throughput evaluation of drug disposition during drug discovery.

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This study was aimed at evaluating changes in CYP3A activity following and during pregnancy by analyzing metabolic markers for CYP3A activity, which can help avoid unnecessary drug exposure and invasive sampling.

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Cytochrome P450 2J2 (CYP2J2) is involved in the metabolism of drugs, including albendazole, astemizole, ebastine, and endogenous substrates. In a previous study, we used recombinant CYP2J2 and determined whether danazol, hydroxyebastine, telmisartan, and terfenadone inhibited CYP2J2 by using four representative CYP2J2 substrates, namely albendazole, astemizole, ebastine, and terfenadine. In this study, we evaluated the inhibitory potential of these four chemicals on human liver and intestinal microsomes, which are commonly used in a reaction phenotyping study. Among the four CYP2J2 inhibitors tested, terfenadone was strongest inhibitor of CYP2J2-mediated metabolism of albendazole, astemizole, and terfenadine with IC50 values of 0.31, 0.15, and 2.11 μM, respectively, in human liver microsomes (HLMs). In addition, terfenadone had strong inhibitory effect on the metabolism of the abovementioned drugs in human intestinal microsomes (HIMs), with IC50 values of 0.43, 0.08 and 1.07 μM, respectively. Danazol, weakly inhibited CYP2J2-mediated metabolism of albendazole and astemizole with IC50 values of 13.8 and 18.3 μM, respectively in HLMs, whereas it strongly inhibited the CYP2J2-mediated ebastine hydroxylase activity in HLMs and HIMs (IC50 = 1.93-1.95 μM). Our data suggest that terfenadone may be used as a general CYP2J2 inhibitor in reaction phenotyping study using HLMs and HIMs regardless of the substrate used.

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Fisetin is a flavonol compound commonly found in edible vegetables and fruits. It has anti-tumor, antioxidant, and anti-inflammatory effects. Geraldol, the O-methyl metabolite of fisetin in mice, is reported to suppress endothelial cell migration and proliferation. Although the in vivo and in vitro effects of fisetin and its metabolites are frequently reported, studies on herb-drug interactions have not yet been performed. This study was designed to investigate the inhibitory effect of fisetin and geraldol on eight isoforms of human cytochrome P450 (CYP) by using cocktail assay and LC-MS/MS analysis. The selective inhibition of CYP2C8-catalyzed paclitaxel hydroxylation by fisetin and geraldol were confirmed in pooled human liver microsomes (HLMs). In addition, an IC50shift assay under different pre-incubation conditions confirmed that fisetin and geraldol shows a reversible concentration-dependent, but not mechanism-based, inhibition of CYP2C8. Moreover, Michaelis-Menten, Lineweaver-burk plots, Dixon and Eadie-Hofstee showed a non-competitive inhibition mode with an equilibrium dissociation constant of 4.1 μM for fisetin and 11.5 μM for geraldol, determined from secondary plot of the Lineweaver-Burk plot. In conclusion, our results indicate that fisetin showed selective reversible and non-competitive inhibition of CYP2C8 more than its main metabolite, geraldol, in HLMs.

Concepts: Enzyme kinetics, Metabolism, Cytochrome P450, Paracetamol, CYP2C9, Lineweaver–Burk plot, Michaelis–Menten kinetics, CYP2C8

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ASP7991 is a calcimimetic that acts on the calcium-sensing receptor on parathyroid cell membranes and suppresses parathyroid hormone (PTH) secretion in the treatment of secondary hyperparathyroidism. The mass balance and metabolite profile of [14C]ASP7991 were investigated in six healthy male subjects after a single oral dose of [14C]ASP7991 [1 mg, 18.5 kBq (500 nCi)] in solution. [14C] radioactivity in plasma, urine and feces was analyzed using Accelerator mass spectrometry. ASP7991 was rapidly absorbed, metabolized and excreted. Mean recovery of [14C] radioactivity in urine and feces was 30.08% and 49.31%, respectively, and mean total recovery of [14C] radioactivity was 79.39%. The majority of [14C] radioactivity in urine and feces was excreted within the first 72 h following administration. Seven metabolites were detected in plasma, urine and feces samples, and their structures were determined by mass spectrometry. The main metabolic pathways of ASP7991 in humans were predicted to be N-dealkylation, followed by N-acetylation and taurine conjugation to a carboxylic acid moiety. Our findings show that a mass balance study using micro radioactivity doses is suitable for elucidating the pharmacokinetics of the absorption, metabolism and excretion of administered drugs.

Concepts: Protein, Amino acid, Metabolism, Mass spectrometry, Parathyroid hormone, Parathyroid gland, Hypoparathyroidism, Hyperparathyroidism

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This study was undertaken to evaluate the performance of anti-drug antibody (ADA) assays constructed by each participating company using common samples including ADA, drug and human serum. The ADA assays constructed by each company showed good sensitivity and precision for evaluation of ADA. Cut points for screening and confirmatory assays and assay selectivity were determined by various calculation methods. In evaluations of blind ADA samples, nearly similar results were obtained by the study companies in determinations of whether samples were positive or negative except at the lowest sample concentration (5 ng/mL). In measurement of drug tolerance, for almost samples containing ADA and drugs, more positive results were obtained in assays using acid dissociation compared to those without acid dissociation. Overall, the performance of ADA assays constructed by the 10 companies participating in this study was acceptable in terms of sensitivity and reproducibility for detection and evaluation of immunogenicity in both patients and healthy subjects. On the other hand, based on results for samples containing ADA and drugs, validity of results for ADA assays conducted without acid dissociation was less meaningful and more difficult to evaluate. Thus, acid dissociation was confirmed to be useful for improving drug tolerance.

Concepts: Type I and type II errors, Sensitivity and specificity, Drug, ELISA, ELISPOT, Drug addiction, Selectivity, Illegal drug trade