Open-label Study of Cenobamate Monotherapy in Adult Subjects With Newly Diagnosed or Recurrent Partial-Onset Epilepsy

Inclusion Criteria: 1. Be considered reliable and willing to be available for the study period and are able to record seizures and report adverse events (AEs) himself/herself or have a caregiver who can record seizures and report AEs for them. 2. Male or female subjects 18-74 years of age with a diagnosis of partial-onset seizures (POS) according to the 2017 ILAE Classification of Epileptic Seizures. Diagnosis will be established by clinical history and an electroencephalogram (EEG) consistent with POS. Subjects with a normal EEG could be included provided they met the other diagnostic criteria according to clinical history. 3. Subjects who are newly diagnosed or have recurrent epilepsy and have experienced: 1. At least 2 unprovoked seizures (at least \>24 hours apart) within the 1 year prior to Day 1 of the Treatment Period, of which, at least 1 unprovoked seizure (but below 20 seizures) occurred in the 12 weeks prior to Day 1 of the Treatment Period. OR 2. 1 unprovoked seizure within the 12 weeks prior to Day 1 of the Treatment Period with concomitant information to support an increased risk (\>60%) of a second seizure. In the absence of clear information about recurrence risk, or even knowledge of such information, the default definition of epilepsy originates at the second unprovoked seizure. Subjects who are newly diagnosed and have been prescribed a low dose of 1 ASM for ≤12 weeks can be included if the other ASM can be safely down-titrated/discontinued per Investigator discretion within 6 weeks after the 1st dose of cenobamate. For subjects with recurrent epilepsy, they must have relapsed at least 6 months after the end of the last ASM treatment but can have been prescribed a low dose of 1 ASM for ≤12 weeks if the other ASM can be safely down-titrated/discontinued per Investigator discretion within 6 weeks after the 1st dose of cenobamate. 4. Female subjects are either not of childbearing potential, defined as premenarchal, postmenopausal for at least 1 year or surgically sterile (bilateral tubal ligation, bilateral oophorectomy, or hysterectomy), if of childbearing potential, must comply with an acceptable method of birth control during the study, for at least 4 weeks prior to study entry and for 2 weeks after last dose of study drug. 5. Subject and/or caregiver(s)/legal representative must be willing and able to give informed assent/consent for participation in the study. 6. Subject and their caregiver must be willing and able (in the investigator's opinion) to comply with all study requirements. Exclusion Criteria: 1. Subjects who have only simple partial-onset seizures (focal aware seizures) without motor signs. 2. Subjects who have seizure clusters where individual seizures cannot be counted. 3. Subjects who present with or have a history of Lennox-Gastaut syndrome. 4. Subjects who have a history of status epilepticus that required hospitalization within 1 year prior to Day 1 of the Treatment Period. 5. Subjects who have a history of psychogenic non-epileptic seizures within 2 years prior to Day 1 of the Treatment Period. 6. Subjects who have a history of active suicidal ideation within the last 6 months or suicide attempt within 2 years prior to Day 1 of Treatment Period. 7. Evidence of clinically significant disease (eg, cardiac, respiratory, gastrointestinal, psychiatric, other neurological) that in the opinion of the investigator(s) could affect the subject's safety or interfere with the study assessments. 8. History of Familial Short QT syndrome or prior subject diagnosis of Short QT syndrome. 9. Evidence of clinically significant active renal or hepatic disease. 10. Subjects taking a strong CYP3A inducer such as phenytoin, phenobarbital, carbamazepine, or rifampin within 12 weeks prior to the Pretreatment Period unless emergency care was needed due to the subject experiencing status epilepticus, uncontrolled seizures, or clusters of seizures. 11. Subjects who are taking more than one of the following centrally acting drugs: antipsychotic, antidepressant, or anxiolytic. The dose should be stable for the 12 weeks prior to the Pretreatment Period. 12. Subjects who have a history of any type of surgery for brain or central nervous system within 1 year prior to the Pretreatment Period. 13. Subjects who have a history of receiving any ASM (including ASM used as rescue treatment and ASMs used for indications other than epilepsy) for more than 12 weeks in total within 6 months prior to Day 1 of the Treatment Period. 14. Subjects who have used intermittent rescue medicine on 2 or more occasions within 12 weeks before the Pretreatment Period (1 to 2 doses over a 24-hour period considered one-time rescue). 15. Subjects who have a history of receiving any ASM polytherapy (\> 2 ASMs taken concurrently) during a previous episode of epilepsy. 16. Previous exposure to cenobamate or sensitivity/allergy to components of the oral tablets. 17. Subjects who have a history of drug or alcohol dependency or abuse within the last 2 years before the Pretreatment Period. 18. Subjects who have had multiple drug allergies or a severe drug reaction, including dermatological (eg, DRESS syndrome, Stevens-Johnson syndrome), hematological, or organ toxicity reactions. 19. Females who are breastfeeding or pregnant or planning to get pregnant in the Pretreatment Period or during the conduct of the study. 20. Subjects who have participated in a study involving administration of an investigational drug or device within 4 weeks before Visit 1, or within approximately 5 half-lives of the previous investigational compound, whichever is longer. 21. Subjects with dementia. 22. Subjects who have seizures due to a progressive CNS condition.