Virtual clinical QT exposure-response studies - A translational computational approach.

Background And Purpose: A recent paradigm shift in proarrhythmic risk assessment suggests that the integration of clinical, non-clinical, and computational evidence can be used to reach a comprehensive understanding of the proarrhythmic potential of drug candidates. While current computational methodologies focus on predicting the incidence of proarrhythmic events after drug administration, the objective of this study is to predict concentration-response relationships of QTc as a clinical endpoint.

Experimental Approach: Full heart computational models reproducing human cardiac populations were created to predict the concentration-response relationship of changes in the QT interval as recommended for clinical trials.

Optimization of bioanalysis of dried blood samples.

Introduction: Pharmacokinetic/pharmacodynamic modelling has emerged as a valuable technique for understanding drug exposure and response relationships in drug development. Pharmacokinetic data are often obtained by taking multiple blood samples, which may disturb physiological parameters and complicate study designs. Wearable automatic blood sampling systems can improve this limitation by collecting dried blood samples at programmable time points without disrupting cardiovascular parameters.

Discovery of BI 7446: A Potent Cyclic Dinucleotide STING Agonist with Broad-Spectrum Variant Activity for the Treatment of Cancer.

Activating the stimulator of interferon genes (STING) pathway with STING agonists is an attractive immune oncology concept to treat patients with tumors that are refractory to single-agent anti-PD-1 therapy. For best clinical translatability and broad application to cancer patients, STING agonists with potent cellular activation of all STING variants are desired. Novel cyclic dinucleotide (CDN)-based selective STING agonists were designed and synthesized comprising noncanonical nucleobase, ribose, and phosphorothioate moieties.

Ion Channel Expression and Electrophysiology of Singular Human (Primary and Induced Pluripotent Stem Cell-Derived) Cardiomyocytes.

Subtype-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are promising tools, e.g., to assess the potential of drugs to cause chronotropic effects (nodal hiPSC-CMs), atrial fibrillation (atrial hiPSC-CMs), or ventricular arrhythmias (ventricular hiPSC-CMs).

Characterization of iCell cardiomyocytes using single-cell RNA-sequencing methods.

Introduction: Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes are being evaluated for their use in pharmacological and toxicological testing, particularly for electrophysiological side effects. However, little is known about the composition of the commercially available iCell cardiomyocyte (Fuijifilm Cellular Dynamics) cultures and the transcriptomic phenotype of individual cells.

Methods: We characterized iCell cardiomyocytes (assumed to be a mixture of nodal-, atrial-, and ventricular-like cardiomyocytes together with potential residual non-myocytes) using bulk RNA-sequencing, followed by investigation of cellular heterogeneity using two different single-cell RNA-sequencing platforms.

Comparison of in vitro and computational experiments on the relation of inter-beat interval and duration of repolarization in a specific type of human induced pluripotent stem cell-derived cardiomyocytes.

We compared a published computational model of the action potential of a specific type of human induced pluripotent stem cell -derived cardiomyocytes (hiPSC-CM) with experimental field potential data with regard to their inter-beat interval and the duration of repolarization. In particular, concomitant changes in inter-beat interval and duration of repolarization were calculated after reduction and/or augmentation of specific ion channel conductances as a surrogate for pharmacological manipulation. The observed mismatches between calculations and experimental data indicate that there is information missing about the cellular test system.

In vivo selective inhibition of TRPC6 by antagonist BI 749327 ameliorates fibrosis and dysfunction in cardiac and renal disease.

Transient receptor potential canonical type 6 (TRPC6) is a nonselective receptor-operated cation channel that regulates reactive fibrosis and growth signaling. Increased TRPC6 activity from enhanced gene expression or gain-of-function mutations contribute to cardiac and/or renal disease. Despite evidence supporting a pathophysiological role, no orally bioavailable selective TRPC6 inhibitor has yet been developed and tested in vivo in disease models.

Treatment with HC-070, a potent inhibitor of TRPC4 and TRPC5, leads to anxiolytic and antidepressant effects in mice.

Background: Forty million adults in the US suffer from anxiety disorders, making these the most common forms of mental illness. Transient receptor potential channel canonical subfamily (TRPC) members 4 and 5 are non-selective cation channels highly expressed in regions of the cortex and amygdala, areas thought to be important in regulating anxiety. Previous work with null mice suggests that inhibition of TRPC4 and TRPC5 may have anxiolytic effects.

Influence of field potential duration on spontaneous beating rate of human induced pluripotent stem cell-derived cardiomyocytes: Implications for data analysis and test system selection.

Introduction: Field potential duration in human pluripotent stem cell (hiPSC)-derived cardiomyocytes is discussed as parameter for the assessment of drug-induced delayed repolarization. In spontaneously beating hiPSC-derived cardiomyocytes field potential duration varies depending on beating rate but beating rate can also be influenced by field potential duration. This interdependence is not fully understood and therefore mandates careful data analysis and cautious interpretation of the results.

BI 1002494, a Novel Potent and Selective Oral Spleen Tyrosine Kinase Inhibitor, Displays Differential Potency in Human Basophils and B Cells.

BI 1002494 [(R)-4-{(R)-1-[7-(3,4,5-trimethoxy-phenyl)-[1,6]napthyridin-5-yloxy]-ethyl}pyrrolidin-2-one] is a novel, potent, and selective spleen tyrosine kinase (SYK) inhibitor with sustained plasma exposure after oral administration in rats, which qualifies this molecule as a good in vitro and in vivo tool compound. BI 1002494 exhibits higher potency in inhibiting high-affinity IgE receptor-mediated mast cell and basophil degranulation (IC50 = 115 nM) compared with B-cell receptor-mediated activation of B cells (IC50 = 810 nM). This may be explained by lower kinase potency when the physiologic ligand B-cell linker was used, suggesting that SYK inhibitors may exhibit differential potency depending on the cell type and the respective signal transduction ligand.

An integrated platform for simultaneous multi-well field potential recording and Fura-2-based calcium transient ratiometry in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes.

Introduction: Human induced pluripotent stem cell-derived cardiomyocytes are available from various sources and they are being evaluated for safety testing. Several platforms are available offering different assay principles and read-out parameters: patch-clamp and field potential recording, imaging or photometry, impedance measurement, and recording of contractile force. Routine use will establish which assay principle and which parameters best serve the intended purpose.

Rodent selectivity of piperidine-4-yl-1H-indoles, a series of CC chemokine receptor-3 (CCR3) antagonists: insights from a receptor model.

Rodent selectivity data of piperidine-4-yl-1H-indoles, a series of CC chemokine receptor-3 (CCR3) antagonists, are presented and discussed as part of an overall optimization effort within this lead compound class. Although attachment of an acidic moiety to the 1-position of the indole led to an overall balanced in vitro profile, in particular reducing inhibition of the hERG channel, potency on the rat and mouse receptor worsened. These findings could be rationalized in the context of a CCR3 homology model.

Solubility assessment and on-line exposure confirmation in a patch-clamp assay for hERG (human ether-a-go-go-related gene) potassium channel inhibition.

Introduction: The hERG (human ether-a-go-go-related gene) potassium channel (KV11.1) is an important anti-target in drug discovery as its inhibition by small molecules has considerable promiscuity and is linked to an increased risk of the potentially fatal ventricular arrhythmia torsade de pointes. Therefore, great efforts are taken in the pharmaceutical industry to early on screen out compounds that block the channel.

Restoring long-term potentiation impaired by amyloid-beta oligomers: comparison of an acetylcholinesterase inhibitior and selective neuronal nicotinic receptor agonists.

As nicotinic acetylcholine receptor (nAChR) agonists directly address cholinergic neurotransmission with potential impact on glutamatergic function, they are considered as potential new symptomatic treatment options for Alzheimer's disease compared to the indirectly operating acetylcholinesterase inhibitors such as the current gold standard donepezil. In order to evaluate the therapeutic value of nAChR activation to ameliorate cognitive dysfunction, a direct comparison between α4β2, α7 nAChR agonists, and donepezil was performed on the level of an ex vivo experimental model of impaired memory formation. First, we demonstrated that amyloid beta (Aβ)42 oligomers, which are believed to be the synaptotoxic Aβ-species causally involved in the pathophysiology of Alzheimer's disease, have a detrimental effect on long-term potentiation (LTP) in the CA1 region of rat hippocampal slices, a widely used cellular model of learning and memory.

Inhibition of acetylcholinesterase and phosphodiesterase-9A has differential effects on hippocampal early and late LTP.

Donepezil is the current standard symptomatic treatment of mild-to-moderate Alzheimer's disease (AD) patients. It aims to compensate for the deficit in cholinergic neurotransmission by blocking acetylcholinesterase (AChE) and thus increases the concentration of extracellular acetylcholine. However, experience from clinical practice demonstrated that AChE inhibitors only have moderate treatment effects.

Differential effects of subtype-specific nicotinic acetylcholine receptor agonists on early and late hippocampal LTP.

Brain nicotinic acetylcholine receptors are involved in several neuropsychiatric disorders, e.g. Alzheimer's and Parkinson's diseases, Tourette's syndrome, schizophrenia, depression, autism, attention deficit hyperactivity disorder, and anxiety.

Differential effect of the mGlu5 receptor positive allosteric modulator ADX-47273 on early and late hippocampal LTP.

Conflicting findings are reported in the literature about the involvement of the mGlu5 receptor in hippocampal long-term potentiation (LTP), which might be a consequence of different sub-types of LTP induced by the investigators due to the specific experimental conditions used. A comparable controversy came up in the past concerning the influence of different experimental conditions on the involvement of L-type voltage dependent calcium channels (L-VDCCs) and NMDA receptors in hippocampal LTP. In this study, two stimulation protocols with otherwise identical conditions were used to probe modulatory effects of mGlu5 receptor activation in NMDA receptor and L-VDCCs dependent CA1 LTP: weak high frequency stimulation (20 stimuli at 100 Hz) to induce early LTP and repeated strong high frequency stimulation (3 times 100 stimuli at 100 Hz with 5 min interval) to induce late LTP, which - in contrast to early LTP - was shown to be protein-synthesis dependent.

A multi-slice recording system for stable late phase hippocampal long-term potentiation experiments.

A major challenge in neuroscience is identifying the cellular and molecular processes underlying learning and memory formation. In the past decades, significant progress has been made in understanding cellular and synaptic mechanisms underlying hippocampal learning and memory using long-term potentiation (LTP) experiments in brain slices as a model system. To expedite LTP measurements it is helpful to further optimize such recording systems.

Behavioral deficits and subregion-specific suppression of LTP in mice expressing a population of mutant NMDA receptors throughout the hippocampus.

The NMDA receptor (NMDAR) subunit GluN1 is an obligatory component of NMDARs without a known functional homolog and is expressed in almost every neuronal cell type. The NMDAR system is a coincidence detector with critical roles in spatial learning and synaptic plasticity. Its coincidence detection property is crucial for the induction of hippocampal long-term potentiation (LTP).

Bias-correction of regression models: a case study on hERG inhibition.

In the present work we develop a predictive QSAR model for the blockade of the hERG channel. Additionally, this specific end point is used as a test scenario to develop and evaluate several techniques for fusing predictions from multiple regression models. hERG inhibition models which are presented here are based on a combined data set of roughly 550 proprietary and 110 public domain compounds.

Subcellular localisation of recombinant alpha- and gamma-synuclein.

alpha-Synuclein, a protein implicated in neurodegenerative diseases and of elusive physiological function owes its name to an observed presence in presynaptic and nuclear compartments. However, its nuclear localisation has remained controversial. We expressed synuclein-eGFP fusion proteins in organotypic rat hippocampal slice cultures and murine hippocampal primary neurons using a Sindbis virus expression system.

Potent inhibition of Ca2+ release-activated Ca2+ channels and T-lymphocyte activation by the pyrazole derivative BTP2.

Ca2+ entry through store-operated Ca2+release-activated Ca2+ (CRAC) channels is essential for T-cell activation and proliferation. Recently, it has been shown that 3,5-bistrifluoromethyl pyrazole (BTP) derivatives are specific inhibitors of Ca2+-dependent transcriptional activity in T-cells (Trevillyan, J. M.

Absence of Whisker-related pattern formation in mice with NMDA receptors lacking coincidence detection properties and calcium signaling.

Precise refinement of synaptic connectivity is the result of activity-dependent mechanisms in which coincidence-dependent calcium signaling by NMDA receptors (NMDARs) under control of the voltage-dependent Mg2+ block might play a special role. In the developing rodent trigeminal system, the pattern of synaptic connections between whisker-specific inputs and their target cells in the brainstem is refined to form functionally and morphologically distinct units (barrelettes). To test the role of NMDA receptor signaling in this process, we introduced the N598R mutation into the native NR1 gene.