Mucin-Protected Caco-2 Assay to Study Drug Permeation in the Presence of Complex Biorelevant Media

The poor solubility and permeability of compounds beyond Lipinski’s Rule of Five (bRo5) are major challenges for cell-based permeability assays. Due to their incompatibility with gastrointestinal components in biorelevant media, the exploration of important questions addressing food effects is limited. Thus, we established a robust mucin-protected Caco-2 assay to allow the assessment of drug permeation in complex biorelevant media. To do that, the assay conditions were first optimized with dependence of the concentration of porcine mucin added to the cells. Mucin-specific effects on drug permeability were evaluated by analyzing cell permeability values for 15 reference drugs (BCS class I–IV). Secondly, a sigmoidal relationship between mucin-dependent permeability and fraction absorbed in human (f_a) was established. A case study with venetoclax (BCS class IV) was performed to investigate the impact of medium complexity and the prandial state on drug permeation. Luminal fluids obtained from the tiny-TIM system showed a higher solubilization capacity for venetoclax, and a better read-out for the drug permeability, as compared to FaSSIF or FeSSIF media. In conclusion, the mucin-protected Caco-2 assay combined with biorelevant media improves the mechanistic understanding of drug permeation and addresses complex biopharmaceutical questions, such as food effects on oral drug absorption.

Collecting antibodies and large molecule biomarkers in mouse interstitial brain fluid: a comparison of microdialysis and cerebral open flow microperfusion

The determination of concentrations of large therapeutic molecules, like monoclonal antibodies (mAbs), in the interstitial brain fluid (ISF) is one of the cornerstones for the translation from preclinical species to humans of treatments for neurodegenerative diseases. Microdialysis (MD) and cerebral open flow microperfusion (cOFM) are the only currently available methods for extracting ISF, and their use and characterization for the collection of large molecules in rodents have barely started. For the first time, we compared both methods at a technical and performance level for measuring ISF concentrations of a non-target-binding mAb, trastuzumab, in awake and freely moving mice. Without correction of the data for recovery, concentrations of samples are over 10-fold higher through cOFM compared to MD. The overall similar pharmacokinetic profile and ISF exposure between MD (corrected for recovery) and cOFM indicate an underestimation of the absolute concentrations calculated with in vitro recovery. In vivo recovery (zero-flow rate method) revealed an increased extraction of trastuzumab at low flow rates and a 6-fold higher absolute concentration at steady state than initially calculated with the in vitro recovery. Technical optimizations have significantly increased the performance of both systems, resulting in the possibility of sampling up to 12 mice simultaneously. Moreover, strict aseptic conditions have played an important role in improving data quality. The standardization of these complex methods makes the unraveling of ISF concentrations attainable for various diseases and modalities, starting in this study with mAbs, but extending further in the future to RNA therapeutics, antibody-drug conjugates, and even cell therapies.

Quantitative Systems Toxicology Modeling To Address Key Safety Questions in Drug Development: A Focus of the TransQST Consortium

Omics data have been increasingly generated with limited demonstrated value in drug safety assessment. The TransQST consortium was launched to use omics and other data in mechanistic-based quantitative systems toxicology (QST) models to evaluate their potential use in species translation.

Quantitative Systems Pharmacology Model for Alzheimer Disease Indicates Targeting Sphingolipid Dysregulation as Potential Treatment Option

Alzheimer disease (AD) is a devastating neurodegenerative disorder with high unmet medical need. Drug development is hampered by limited understanding of the disease and its driving factors. Quantitative Systems Pharmacology (QSP) modeling provides a comprehensive quantitative framework to evaluate the relevance of biological mechanisms in the context of disease and to predict the efficacy of novel treatments. Here, we report a QSP model for AD with a particular focus on investigating the relevance of dysregulation of cholesterol and sphingolipids. We show that our model captures the modulation of several biomarkers in subjects with AD, as well as the response to pharmacological interventions. We evaluate the impact of targeting the sphingosine-1-phosphate 5 receptor (S1PR5) as a potential novel treatment option for AD, and model predictions increase our confidence in this novel disease pathway. Future applications for the QSP model are in validation of further targets and identification of potential treatment response biomarkers.

IMI - oral biopharmaceutics tools project - evaluation of bottom-up PBPK prediction success part 1: Characterisation of the OrBiTo database of compounds

Predicting oral bioavailability (F_oral) is of importance for estimating systemic exposure of orally administered drugs. Physiologically-based pharmacokinetic (PBPK) modelling and simulation have been applied extensively in biopharmaceutics recently. The Oral Biopharmaceutical Tools (OrBiTo) project (Innovative Medicines Initiative) aims to develop and improve upon biopharmaceutical tools, including PBPK absorption models. A large-scale evaluation of PBPK models may be considered the first step. Here we characterise the OrBiTo active pharmaceutical ingredient (API) database for use in a large-scale simulation study. The OrBiTo database comprised 83 APIs and 1475 study arms. The database displayed a median logP of 3.60 (2.40-4.58), human blood-to-plasma ratio of 0.62 (0.57-0.71), and fraction unbound in plasma of 0.05 (0.01-0.17). The database mainly consisted of basic compounds (48.19%) and Biopharmaceutics Classification System class II compounds (55.81%). Median human intravenous clearance was 16.9L/h (interquartile range: 11.6-43.6L/h; n=23), volume of distribution was 80.8L (54.5-239L; n=23). The majority of oral formulations were immediate release (IR: 87.6%). Human F_oral displayed a median of 0.415 (0.203-0.724; n=22) for IR formulations. The OrBiTo database was found to be largely representative of previously published datasets. 43 of the APIs were found to satisfy the minimum inclusion criteria for the simulation exercise, and many of these have significant gaps of other key parameters, which could potentially impact the interpretability of the simulation outcome. However, the OrBiTo simulation exercise represents a unique opportunity to perform a large-scale evaluation of the PBPK approach to predicting oral biopharmaceutics.

Generation and Characterization of a Breast Cancer Resistance Protein Humanized Mouse Model

Breast cancer resistance protein (BCRP) is expressed in various tissues, such as the gut, liver, kidney and blood brain barrier (BBB), where it mediates the unidirectional transport of substrates to the apical/luminal side of polarized cells. Thereby BCRP acts as an efflux pump, mediating the elimination or restricting the entry of endogenous compounds or xenobiotics into tissues and it plays important roles in drug disposition, efficacy and safety. Bcrp knockout mice (Bcrp(-/-)) have been used widely to study the role of this transporter in limiting intestinal absorption and brain penetration of substrate compounds. Here we describe the first generation and characterization of a mouse line humanized for BCRP (hBCRP), in which the mouse coding sequence from the start to stop codon was replaced with the corresponding human genomic region, such that the human transporter is expressed under control of the murineBcrppromoter. We demonstrate robust human and loss of mouse BCRP/Bcrp mRNA and protein expression in the hBCRP mice and the absence of major compensatory changes in the expression of other genes involved in drug metabolism and disposition. Pharmacokinetic and brain distribution studies with several BCRP probe substrates confirmed the functional activity of the human transporter in these mice. Furthermore, we provide practical examples for the use of hBCRP mice to study drug-drug interactions (DDIs). The hBCRP mouse is a promising model to study the in vivo role of human BCRP in limiting absorption and BBB penetration of substrate compounds and to investigate clinically relevant DDIs involving BCRP.

N-methyl-D-aspartate but not glutamate induces the release of hydroxyl radicals in the neonatal rat: modulation by group I metabotropic glutamate receptors

Although they likely involve activation of N-methyl-D-aspartate (NMDA) receptors, the mechanisms giving rise to perinatal hypoxic-ischemic-induced damages remained unclear. The purpose of the present study was to investigate in vivo the mechanisms regulating the glutamate-induced release of toxic hydroxyl radicals (.OH) in neonatal rat. Anesthetized 7-day-old Wistar rat pups bearing a microdialysis cannula implanted in the striatum were perfused with a solution containing salicylate as an.OH trap. Hydroxyl radicals formation was evaluated, after a 3 hr postoperative delay, by measuring the 2,3-DHBA levels by HPLC/EC before, during and over 3 hr after the administration of glutamatergic agonists or antagonists. Administration of NMDA and of ibotenate dramatically increased the efflux of.OH, 17-fold and sixfold, respectively. Glutamate, used at the same concentration did not produce any significant increase in the.OH release and may even decrease this efflux when given at larger concentrations. The NMDA-induced.OH response was partially but progressively reduced by glutamate coinjection and completely blunted by DHPG [(RS)-3, 5-dihydroxyphenylglycine], a group I metabotropic glutamate receptor agonist. Conversely, AIDA [(RS)-1-aminoindan-1,5-dicarboxylic acid], an antagonist of the same receptors, unmasked an.OH response to glutamate. These results are evidence that the glutamate-induced activation of a group I metabotropic glutamate receptor normally protected the neonatal brain from any glutamate activation of NMDA receptor, which otherwise would produce the release of toxic hydroxyl radicals. Targeting group I metabotropic glutamate receptors and/or.OH might contribute to protecting the neonatal brain against perinatal hypoxic-ischemic induced lesions.

The novel non-competitive N-methyl-D-aspartate antagonist gacyclidine blocks the glutamate-induced release of hydroxyl radicals in the striatum under conditions in which dizocilpine does not. A microdialysis study in rats

Gacyclidine, a new neuroprotectant aimed to non-competitively antagonize N-methyl-D-aspartate (NMDA) receptors, and dizocilpine blocked the hydroxyl radical response to toxic amounts of glutamate, perfused through a microdialysis implanted in the striatum of conscious rats. Furthermore, the hydroxyl radical response resulting from the infusion of lower doses of glutamate, which could not be inhibited by the same amounts of dizocilpine nor by acute alcohol exposure, still remained sensitive to gacyclidine inhibition. Thus, oxidative stress resulting from a glutamate discharge involves the activation of both NMDA receptors, and of non-NMDA mechanism(s) which, with moderate glutamate levels, were still antagonized by gacyclidine. Enhanced blockage of toxic hydroxyl radicals might explain the different and possibly higher neuroprotective property of gacyclidine as compared with other non-competitive NMDA antagonists.