Cenobamate (YKP3089) is an antiepileptic drug recently approved by the Food and Drug Administration for the treatment of focal (partial-onset) seizures in adults. The objectives of a first-in-human single-ascending-dose study and 3 multiple-ascending-dose studies were to characterize the pharmacokinetics, safety, and tolerability of cenobamate after single-dose and multiple-dose administration in healthy subjects. The 4 randomized, placebo-controlled, doubleblind studies were conducted in 210 healthy subjects receiving single (5 to 750 mg) or multiple (50 to 600 mg/day) oral doses of cenobamate or placebo using capsule formulation. Safety assessments included treatment-emergent adverse events (TEAEs) and laboratory evaluations. Maximum plasma concentrations of cenobamate were observed between 0.8 and 4.0 hours after oral administration. C max increased in a dose-proportional manner for single-and multiple-dose administration across all tested doses. Although the AUC of cenobamate increased in a more than dose-proportional manner after single-dose administration, a dose-proportional increase in cenobamate AUC τ was observed after multiple dosing from 50 to 500 mg/day. Cenobamate exhibited low oral clearance (decreasing from approximately 1.4 to 0.50 L/h with dose increase) and long terminal half-life (range, approximately 30 to 76 hours with increasing dose). Steady-state was attained after approximately 2 weeks, and the accumulation ratio was approximately 5 over the 50 to 300 mg/day range. The pharmacokinetic characteristics of cenobamate are consistent with once-daily dosing. Most TEAEs were mild in severity, 2 serious TEAEs were reported, and no deaths occurred across all studies. Except for multiple daily doses of 600 mg, all doses were generally well tolerated.Despite the development of more than a dozen new antiepileptic drugs (AEDs) over the past 20 years, significant progress in improving the efficacy and tolerability of therapies for patients with epilepsy has been limited by the efficacy and safety of these compounds. [1][2][3][4][5] Approximately 30% to 56% of patients with epilepsy continue to experience uncontrolled seizures during therapy with existing AEDs. 2,3,5,6 Continued seizures despite AED treatment have been associated with increased risk of mood disorders, limitations in education and work opportunities, and greater stigma for patients. 7 Many patients report reduced quality of life because of the failure of existing AEDs to control seizures or because of their intolerable side effects. 7,8 Thus, there remains a clear unmet need for new AEDs that are effective, safe, and tolerable. Cenobamate (YKP3089) is an AED recently approved by the US Food and Drug Administration (FDA) for the treatment of adults with focal (partialonset) seizures (Supplemental Figure). Although the mechanism by which cenobamate exerts its therapeutic effect has yet to be fully elucidated, it has been shown to involve enhancement of fast and slow inactivation of