Nonclinical Cardiovascular Assessment of the Soluble Guanylate Cyclase Stimulator Vericiguat.

Vericiguat and its metabolite M-1 were assessed for proarrhythmic risk in nonclinical in vitro and in vivo studies. In vitro manual voltage-clamp recordings at room temperature determined the effect of vericiguat on human Ether-a-go-go Related Gene (hERG) K+ channels. Effects of vericiguat and M-1 on hERG K+, Nav1.5, hCav1.2, hKvLQT1/1minK, and hKv4.3 channels were investigated via automated voltage-clamp recordings at ambient temperature. Effects of vericiguat and M-1 on hERG K+ and Nav1.5 channels at pathophysiological conditions were explored via manual voltage-clamp recordings at physiologic temperature. Single oral doses of vericiguat (0.6, 2.0, and 6.0 mg/kg) were assessed for in vivo proarrhythmic risk via administration to conscious telemetered dogs; electrocardiogram (ECG) and hemodynamic parameters were monitored. ECG recordings were included in 4- and 39-week dog toxicity studies. In manual voltage-clamp recordings, vericiguat inhibited hERG K+-mediated tail currents in a concentration-dependent manner (20% threshold inhibitory concentration ∼1.9 µM). In automated voltage-clamp recordings, neither vericiguat nor M-1 were associated with biologically relevant inhibition (>20%) of hNav1.5, hCav1.2, hKvLQT1, and hKv4.3. No clinically relevant observations were made for hNav1.5 and hKvLQT1 under simulated pathophysiological conditions. Vericiguat was associated with expected mode-of-action-related dose-dependent changes in systolic arterial blood pressure (up to -20%) and heart rate (up to +53%). At maximum vericiguat dose, corrected QT (QTc) interval changes from baseline varied slightly (-6 to +1%) depending on correction formula. Toxicity studies confirmed absence of significant QTc interval changes. There was no evidence of an increased proarrhythmic risk from nonclinical studies with vericiguat or M-1. SIGNIFICANCE STATEMENT: There was no evidence of an increased proarrhythmic risk from in vitro and in vivo nonclinical studies with vericiguat or M-1. The integrated risk assessment of these nonclinical data combined with existing clinical data demonstrate administration of vericiguat 10 mg once daily in patients with heart failure with reduced ejection fraction is not associated with a proarrhythmic risk.

Sensitivity, specificity and limitation of in vitro hippocampal slice and neuron-based assays for assessment of drug-induced seizure liability.

An effective in vitro screening assay to detect seizure liability in preclinical development can contribute to better lead molecule optimization prior to candidate selection, providing higher throughput and overcoming potential brain exposure limitations in animal studies. This study explored effects of 26 positive and 14 negative reference pharmacological agents acting through different mechanisms, including 18 reference agents acting on glutamate signaling pathways, in a brain slice assay (BSA) of adult rat to define the assay's sensitivity, specificity, and limitations. Evoked population spikes (PS) were recorded from CA1 pyramidal neurons of hippocampus (HPC) in the BSA. Endpoints for analysis were PS area and PS number. Most positive references (24/26) elicited a concentration-dependent increase in PS area and/or PS number. The negative references (14/14) had little effect on the PS. Moreover, we studied the effects of 15 reference agents testing positive in the BSA on spontaneous activity in E18 rat HPC neurons monitored with microelectrode arrays (MEA), and compared these effects to the BSA results. From these in vitro studies we conclude that the BSA provides 93% sensitivity and 100% specificity in prediction of drug-induced seizure liability, including detecting seizurogenicity by 3 groups of metabotropic glutamate receptor (mGluR) ligands. The MEA results seemed more variable, both quantitatively and directionally, particularly for endpoints capturing synchronized electrical activity. We discuss these results from the two models, comparing each with published results, and provide potential explanations for differences and future directions.

Time for a Fully Integrated Nonclinical-Clinical Risk Assessment to Streamline QT Prolongation Liability Determinations: A Pharma Industry Perspective.

Defining an appropriate and efficient assessment of drug-induced corrected QT interval (QTc) prolongation (a surrogate marker of torsades de pointes arrhythmia) remains a concern of drug developers and regulators worldwide. In use for over 15 years, the nonclinical International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) S7B and clinical ICH E14 guidances describe three core assays (S7B: in vitro hERG current & in vivo QTc studies; E14: thorough QT study) that are used to assess the potential of drugs to cause delayed ventricular repolarization. Incorporating these assays during nonclinical or human testing of novel compounds has led to a low prevalence of QTc-prolonging drugs in clinical trials and no new drugs having been removed from the marketplace due to unexpected QTc prolongation. Despite this success, nonclinical evaluations of delayed repolarization still minimally influence ICH E14-based strategies for assessing clinical QTc prolongation and defining proarrhythmic risk. In particular, the value of ICH S7B-based "double-negative" nonclinical findings (low risk for hERG block and in vivo QTc prolongation at relevant clinical exposures) is underappreciated. These nonclinical data have additional value in assessing the risk of clinical QTc prolongation when clinical evaluations are limited by heart rate changes, low drug exposures, or high-dose safety considerations. The time has come to meaningfully merge nonclinical and clinical data to enable a more comprehensive, but flexible, clinical risk assessment strategy for QTc monitoring discussed in updated ICH E14 Questions and Answers. Implementing a fully integrated nonclinical/clinical risk assessment for compounds with double-negative nonclinical findings in the context of a low prevalence of clinical QTc prolongation would relieve the burden of unnecessary clinical QTc studies and streamline drug development.

Multi-parametric assessment of cardiomyocyte excitation-contraction coupling using impedance and field potential recording: A tool for cardiac safety assessment.

INTRODUCTION: The ICH S7B guidelines recommend that all new chemical entities should be subjected to hERG repolarization screening due to its association with life-threatening "Torsades de Pointes" (TdP) arrhythmia. However, it has become evident that not all hERG channel inhibitors result in TdP and not all compounds that induce QT prolongation and TdP necessarily inhibit hERG. In order to address the limitations of the S7B/E14 guidelines, the FDA through a public/private partnership initiated the Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative to examine the possible modification and refinement of the ICH E14/S7B guidelines. One of the main components of the CiPA initiative is to utilize a predictive assay system together with human cardiomyocytes for risk assessment of arrhythmia. METHOD: In this manuscript we utilize the xCELLigence® CardioECR system which simultaneously measures excitation-contraction coupling together with human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) to assess the effect of 8 reference compounds across 3 different independent sites. These 8 compounds were part of Phase I CiPA validation study. RESULTS: Our data demonstrate that hERG channel blockers, such as E4031 and moxifloxacin, prolonged field potential duration (FPD) at low concentration and induced arrhythmic beating activity as measured by field potential (FP) recording and impedance (IMP) recordings at higher concentrations. On the contrary, nifedipine, an inhibitor of calcium channel, didn't disrupt the periodicity of cell beating and weakened cell contractile activity and shortened FPD. Multichannel inhibitors, such as flecainide, quinidine and mexiletine, not only increased FPD and induced arrhythmia but also significantly reduced the amplitude of FP spike. JNJ303, an IKs inhibitor, only affected FPD. Comparison of the compound effect on FPD across the 3 different sites is consistent in terms of trend of the effect with observed 3-10 fold differences in minimal effective concentration at which a minimum of 10% response is detected. In addition, pentamidine, a hERG trafficking inhibitor which induced irregular beating activity over a more prolonged duration of time was readily flagged in this assay system. Taken together, this multi-parameter assay using hiPSC-CMs in conjunction with simultaneous measurement of ion channel activity and contractility can be a reliable approach for risk assessment of proarrhythmic compounds.

Nonclinical safety assessment of the histone deacetylase inhibitor vorinostat.

Vorinostat (SAHA, Zolinza), a histone deacetylase inhibitor, is assessed in nonclinical studies to support its approval for cutaneous T-cell lymphoma. Vorinostat is weakly mutagenic in the Ames assay; is clastogenic in rodent (ie, CHO) cells but not in normal human lymphocytes; and is weakly positive in an in vivo mouse micronucleus assay. No effects are observed on potassium ion currents in the hERG assay up to 300 microM (safety margin approximately 300-fold the approximately 1 microM serum concentration associated with the 400 mg/d maximum recommended human dose. No rat respiratory or central nervous system effects are found at 150 mg/kg (>2-fold maximum recommended human dose). No cardiovascular effects, including effects on QTc interval, are observed after a single oral dose (150 mg/kg) in dogs. Vorinostat is orally dosed daily in rats (controls, 20, 50, or 150 mg/kg/d) and dogs (controls, 60, 80, or 100/125/160 mg/kg/d) for 26 weeks with a 4-week recovery. Rat vorinostat-related adverse findings are decreased food consumption, weight loss, and hematologic changes; a no observed adverse effects level is not established. In dogs, adverse effects are primarily gastrointestinal; the no observed adverse effects level is 60 mg/kg/d (approximately 6-fold maximum recommended human dose). Toxicities are reversible and can be monitored in the clinic.