Drug-induced liver injury is the most common cause of market withdrawal of pharmaceuticals, and thus, there is considerable need for better prediction models for DILI early in drug discovery. We present a study involving 223 marketed drugs (51% associated with clinical hepatotoxicity; 49% non-hepatotoxic) to assess the concordance of in vitro bioactivation data with clinical hepatotoxicity and have used these data to develop a decision tree to help reduce late-stage candidate attrition. Data to assess P450 metabolism-dependent inhibition (MDI) for all common drug-metabolizing P450 enzymes were generated for 179 of these compounds, GSH adduct data generated for 190 compounds, covalent binding data obtained for 53 compounds, and clinical dose data obtained for all compounds.
View Article and Find Full Text PDFOATP1A2 is expressed in the luminal membrane of human blood-brain barrier (BBB). The human tissue with the highest OATP1A2 mRNA expression is the brain. We have established a robust BacMam2-OATP1A2 transduced HEK293 system.
View Article and Find Full Text PDFFrom previous fits of drug transport kinetics across confluent Madin-Darby canine kidney II cell line overexpressing human multidrug resistance 1 cell monolayers, we found that a drug's binding constant to P-glycoprotein (P-gp) was significantly smaller than its IC(50) when that drug was used as an inhibitor against another P-gp substrate. We tested several IC(50) candidate functions, including the standard function, the Kalvass-Pollack function, and the efflux ratio, to determine whether any of them yielded an IC(50) = K(I), as would be expected for water-soluble enzymes. For the confluent cell monolayer, the IC(50)/K(I) ratio is greater than 1 for all candidate functions tested.
View Article and Find Full Text PDFThe Biopharmaceutics Classification System (BCS) is the scientific basis for classifying drugs based on their aqueous solubility and intestinal permeability that supports in vivo bioavailability and bioequivalence waivers for immediate-release solid dosage form drugs. One requirement of the BCS is that the permeability method must be validated. In order to accommodate the variety of in vitro/in situ permeability models, the BCS Guidance gives a general framework for the validation requirements, necessitating implemented experimental details to be selected by the applicant laboratory.
View Article and Find Full Text PDFThe objective of this investigation is to characterize the role of complex biophase distribution kinetics in the pharmacokinetic-pharmacodynamic correlation of a wide range of opioids. Following intravenous infusion of morphine, alfentanil, fentanyl, sufentanil, butorphanol and nalbuphine the time course of the EEG effect was determined in conjunction with blood concentrations. Different biophase distribution models were tested for their ability to describe hysteresis between blood concentration and effect.
View Article and Find Full Text PDFA robust screen for compound interaction with P-glycoprotein (P-gp) has some obvious requirements, such as a cell line expressing P-gp and a probe substrate that is transported solely by P-gp and passive permeability. It is actually difficult to prove that a particular probe substrate interacts only with P-gp in the chosen cell line. Using a confluent monolayer of MDCKII-hMDR1 cells, we have determined the elementary rate constants for the P-gp efflux of amprenavir, digoxin, loperamide, and quinidine.
View Article and Find Full Text PDFThe multidrug resistance transporter P-glycoprotein (P-gp) effluxes a wide range of substrates and can be affected by a wide range of inhibitors or modulators. Many studies have presented classifications for these binding interactions, within either the context of equilibrium binding or the Michaelis-Menten enzyme analysis of the ATPase activity of P-gp. Our approach is to study P-gp transport and its inhibition using a physiologically relevant confluent monolayer of hMDR1-MDCKII cells.
View Article and Find Full Text PDFDrug-induced changes in expression of cytochrome P450 (P450) genes are a significant issue in the preclinical development of pharmaceuticals. For example, preclinically, P450 induction can affect safety studies by reducing the systemic exposure of a compound undergoing toxicological evaluation, thus limiting the exposure that can be safely investigated in patients. Therefore, the induction potential of candidate drugs has been studied as part of the drug development process, typically using protein and/or catalytic end points.
View Article and Find Full Text PDFPurpose: Typically, the kinetics of membrane transport is analyzed using the steady-state Michaelis-Menten (or Eadie-Hofstee or Hanes) equations. This approach has been successful when the substrate is picked up from the aqueous phase, like a water-soluble enzyme, for which the Michaelis-Menten steady-state analysis was developed. For membrane transporters whose substrate resides in the lipid bilayer of the plasma membrane, like P-glycoprotein (P-gp), there has been no validation of the accuracy of the steady-state analysis because the elementary rate constants for transport were not known.
View Article and Find Full Text PDFThe novel 8-piperazinyl-2,3-dihydropyrroloisoquinoline template was synthesized in nine steps. The template was N-substituted to give a series of compounds showing binding to human cloned 5-HT1A, 5-HT1B and 5-HT1D receptors with pKi's greater than 9 and selectivities up to 1000-fold against other serotonin, dopamine and adrenergic receptors. Several compounds were shown to possess weak partial agonist activity in cloned receptors, which translated to antagonism in in vitro studies.
View Article and Find Full Text PDFThe human multi-drug resistance membrane transporter, P-glycoprotein, or P-gp, has been extensively studied due to its importance to human health and disease. Thus far, the kinetic analysis of P-gp transport has been limited to steady-state Michaelis-Menten approaches or to compartmental models, neither of which can prove molecular mechanisms. Determination of the elementary kinetic rate constants of transport will be essential to understanding how P-gp works.
View Article and Find Full Text PDFKnowledge of the passive permeability coefficient for new drugs is useful for estimating the fraction absorbed across the gastrointestinal tract. The commonly used approximate formula for the passive permeability coefficient is based on the initial rate of permeation across cell monolayers, requires measurement during the linear phase of permeation, and is not applicable when there is significant back flux of compound or mass balance problem. To develop a rigorous equation that can be used at any time point, i.
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