Effects of cenobamate (YKP3089), a newly developed anti-epileptic drug, on voltage-gated sodium channels in rat hippocampal CA3 neurons

New, more effective pharmacologic treatments for epilepsy are needed, as a substantial portion of patients ( > 30%) are refractory to currently available anti-epileptic drugs. Cenobamate (YKP3089) is an investigational anti-epileptic drug in clinical development. Two completed adequate and well-controlled studies demonstrated a significant reduction in focal seizures with cenobamate in patients with epilepsy. In this study, we characterized the effects of cenobamate on voltage-gated Na+ channels in acutely isolated rat hippocampal CA3 neurons using a whole-cell patch-clamp technique. While cenobamate had little effect on the peak component of transient Na+ current (I-NaT) induced by brief depolarizing step pulses, it potently inhibited the non-inactivating persistent component of I-Na (I-Nap). In addition, cenobamate potently inhibited the current by slow voltage-ramp stimuli. Cenobamate significantly shifted the steady-state fast inactivation relationship toward a hyperpolarizing range, indicating that cenobamate binds to voltage-gated Na+ channels at the inactivated state with a higher affinity. Cenobamate also accelerated the development of inactivation and retarded recovery from inactivation of voltage-gated Na+ channels. In current clamp experiments, cenobamate hyperpolarized membrane potentials in a concentration-dependent manner, and these effects were mediated by inhibiting the I-Nap. Cenobamate also increased the threshold for generation of action potentials, and decreased the number of action potentials elicited by depolarizing current injection. Given that the I-Nap plays a pivotal role in the repetitive and/or burst generation of action potentials, the cenobamate-mediated preferential blockade of I-Nap might contribute to anti-epileptic activity.