Naohiro Kohmura

Perampanel: A novel, orally active, noncompetitive AMPA‐receptor antagonist that reduces seizure activity in rodent models of epilepsy

Purpose:  To assess the pharmacology of perampanel and its antiseizure activity in preclinical models. Perampanel [2‐(2‐oxo‐1‐phenyl‐5‐pyridin‐2‐yl‐1,2‐dihydropyridin‐3‐yl) benzonitrile] is a novel, orally active, prospective antiepileptic agent currently in development for refractory partial‐onset seizures.

A novel method of selecting human embryonic stem cell-derived cardiomyocyte clusters for assessment of potential to influence QT interval.

Physiologically relevant assessment of delayed repolarization is necessary in drug development. In our preliminary experiments on the evaluation using a multielectrode recording system, we had found that the responsiveness of field potential duration (FPD), as QT-like intervals, to hERG channel blockers differed greatly from non-responders to excessive responders in human embryonic stem cell-derived cardiomyocyte clusters. Thus, we report a novel method of selecting clusters suitable for evaluating compounds for the assessment. Clusters were treated with cisapride, a hERG channel blocker, at 100nM, and selected with criteria of 5-20% of corrected FPD (FPDc) prolongation. Then, selected clusters were treated with reference compounds. FPDc was prolonged by blockade of the hERG channel (E-4031 and dl-sotalol) and KvLQT1 channel (chromanol 293B and HMR1556), and by activation of the sodium channel (veratridine) and calcium channel (Bay K8644). FPDc was shortened by calcium channel blockage (verapamil, nifedipine and diltiazem) and by K(ATP) channel activation (pinacidil). Class Ia antiarrhythmic drugs, quinidine and disopyramide, prolonged FPDc. Selected clusters are appropriate for assessing the effects of compounds on ion channels affecting QT intervals. This is the first report of the establishment of an assessment system of potential to influence QT interval, using pharmacologically selected clusters.

Characterization of Human Hippocampal Neural Stem/Progenitor Cells and Their Application to Physiologically Relevant Assays for Multiple Ionotropic Glutamate Receptors

The hippocampus is an important brain region that is involved in neurological disorders such as Alzheimer disease, schizophrenia, and epilepsy. Ionotropic glutamate receptors—namely, N-methyl-D-aspartate (NMDA) receptors (NMDARs), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors (AMPARs), and kainic acid (KA) receptors (KARs)—are well known to be involved in these diseases by mediating long-term potentiation, excitotoxicity, or both. To predict the therapeutic efficacy and neuronal toxicity of drug candidates acting on these receptors, physiologically relevant systems for assaying brain region–specific human neural cells are necessary. Here, we characterized the functional differentiation of human fetal hippocampus–derived neural stem/progenitor cells—namely, HIP-009 cells. Calcium rise assay demonstrated that, after a 4-week differentiation, the cells responded to NMDA (EC50 = 7.5 ± 0.4 µM; n = 4), AMPA (EC50 = 2.5 ± 0.1 µM; n = 3), or KA (EC50 = 33.5 ± 1.1 µM; n = 3) in a concentration-dependent manner. An AMPA-evoked calcium rise was observed in the absence of the desensitization inhibitor cyclothiazide. In addition, the calcium rise induced by these agonists was inhibited by antagonists for each receptor—namely, MK-801 for NMDA stimulation (IC50 = 0.6 ± 0.1 µM; n = 4) and NBQX for AMPA and KA stimulation (IC50 = 0.7 ± 0.1 and 0.7 ± 0.03 µM, respectively; n = 3). The gene expression profile of differentiated HIP-009 cells was distinct from that of undifferentiated cells and closely resembled that of the human adult hippocampus. Our results show that HIP-009 cells are a unique tool for obtaining human hippocampal neural cells and are applicable to systems for assay of ionotropic glutamate receptors as a physiologically relevant in vitro model.