Abstracts

Rationale:
Epilepsy is caused by abnormal excessive or synchronous neuronal activities in the brain. Many anti-epileptic drugs would inhibit hyper-excitability associated with seizures in excitatory circuits. However, a portion of epilepsy is difficult to treat with existing drugs. Mesial temporal lobe epilepsy (MTLE) is one of the most common refractory epilepsy. Astrocytes regulate a key role against the potassium and glutamate levels in MTLE. A neuronal activity is regulated by potassium and glutamate balance, caused by inwardly rectifying potassium channels 4.1 (Kir4.1) that hyperpolarize the astrocytes resting membrane potential. Conditional knockout mice targeted to astrocytes Kir4.1 demonstrate astrocyte membrane depolarization, glutamate uptake inhibition, and seizures (J Neurosci. 2007 27(42):11354). Furthermore, a decrease in Kir4.1 expression is related to nerve abnormal excitement of hippocampal tissue in human MTLE (EBioMedicine. 2018 29:38).
Method:
The Kir and hERG current was measured by automated patch clamp technique with SyncroPatch 384PE or QPatch II. As the seizure model, we used audiogenic seizure (AGS) and maximal electroshock seizure (MES) models. The AGS response was scored, i.e. 0: no response, 1: wild running, 2: clonic seizure, 3: tonic seizure in male DBA/2N mice. In the MES model, CD1 mice were received an electrical stimulus to ears to evoke tonic hind limb extension. The intrahippocampal kainate mouse model was used as MTLE model using adult male C57BL/6J mice, equipped with an implant electrode (data for electroencephalographic). Hippocampal paroxysmal discharges (HPDs) were defined as sequence of higher frequency spikes and waves lasting at least 5 s and spike frequency ≥ 2 Hz. Rotarod test was assessed by the falling latency in male CD1 mice. All animal tests were performed by oral administration of NCC-1566.
Results:
NCC-1566 is a potent Kir activator (EC50 = 70 nM). NCC-1566 did not inhibit hERG current up to 30 µM. In AGS model, NCC 1566 suppressed clonic and tonic seizure with ED50 = 5 mg/kg (N=8). NCC 1566 showed 100 % protection against MES seizure at 30 mg/kg (N=8). In MTLE model, NCC 1566 significantly reduced HPD counts and duration at 100 mg/kg (N=4). NCC 1566 did not show an impairment of rotarod performance with the test dose.
Conclusion:
We discovered the first in class novel small molecule Kir activator (NCC 1566). Our data suggest that NCC 1566 has an excellent in vivo anti-convulsant, anti-epileptic activity and safety. NCC 1566 represents the first evidence that Kir activator improves animal models of epilepsy. The Kir activator would provide a new treatment option for refractory epilepsy patients.
Funding:
:No funding