The primary purpose of this study is to evaluate the efficacy of perampanel monotherapy measured by the seizure-free rate during the Maintenance Period (24 weeks) of the Treatment Phase in untreated participants with focal onset seizures (FOS) with or without focal to bilateral tonic-clonic seizures (FBTCS).

The study will consist of a Core Study (36 weeks) and an Extension Phase (24 weeks). Core Study will consist of 4 weeks Pre-treatment Phase or Baseline and 32 weeks Treatment Phase (8 weeks Titration period and 24 weeks Maintenance period).

Inclusion Criteria:

1. Male and female, age 4 years or older
2. Diagnosis of epilepsy with FOS with or without FBTCS according to the International League Against Epilepsy (ILAE) Classification of Epileptic Seizures (2017), established by clinical history and an electroencephalogram (EEG)
3. Newly diagnosed or recurrent epilepsy with at least 2 unprovoked seizures (excluding focal non-motor seizures) separated by a minimum of 24 hours in the 1 year before Visit 1 (baseline)

Exclusion Criteria:

1. Focal non-motor seizures only
2. Generalized epilepsies or seizures such as absences and/or myoclonic seizures, or Lennox Gastaut syndrome
3. History of status epilepticus within 1 year before Visit 1 (baseline)
4. History of psychogenic non-epileptic seizures within 5 years before Visit 1 (baseline)
5. Progressive central nervous system (CNS) disease (including degenerative CNS diseases, progressive tumors, and dementia), or clinically significant psychological or neurological disorders
6. History of suicidal ideation/attempt within 5 years before Visit 1 (baseline)
7. Evidence of clinically significant active hepatic disease, or other clinically significant disease (example, cardiac, respiratory, gastrointestinal, renal disease) that in the opinion of the investigators could affect the participant safety or interfere with the study assessments
8. History of any type of brain or central nervous system surgery within 1 year before Visit 1 (baseline)
9. Newly started ketogenic diet or has been on ketogenic diet for less than 5 weeks before Visit 1 (baseline)
10. Multiple drug allergies or a severe drug reaction to anti-epileptic drugs (AEDs), including dermatological (example, Stevens-Johnson syndrome), hematological, or organ toxicity reactions
11. Hypersensitive to perampanel or ingredients of this drug
12. Participant with genetic problems including galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption
13. Use of intermittent rescue medication on 2 or more occasions within 4 weeks before Visit 1 (baseline)
14. History of receiving any AED (except for occasional use less than 2 weeks of AEDs as rescue treatment), antipsychotics, or anti-anxiety drugs within 12 weeks before Visit 1 (baseline)
15. History of receiving any AED (including rescue treatment) for more than 2 weeks in total within 2 years before Visit 1 (baseline)
16. Has received prior treatment with perampanel
17. Females of child bearing potential who are breastfeeding or pregnant at Visit 1 (baseline), or who do not consent to employ contraception
18. Currently enrolled in another clinical study or have used any investigational drug/biologics or device within 28 days or 5*half-life, whichever is longer
19. Participant who did not consent to having at least 2 weeks of washout period before Visit 2, if known to take Cytochrome P4503A (CYP3A) inducing drugs or foods on Visit 1 (including, but not limited to the following) - Carbamazepine, enzalutamide, mitotane, phenytoin, phenobarbital, amobarbital, secobarbital, rifabutin, rifampicin, food containing St. John's Wort (hypericum perforatum), bosentan, efavirenz, etravirine, modafinil, armodafinil, rufinamide, nevirapine, oxcarbazepine, and glucocorticoid (except for topical use)

Eisai's data sharing commitment and further information on how to request data can be found on our website http://eisaiclinicaltrials.com/.