A Study to Investigate JNJ-40411813 in Combination With Levetiracetam or Brivaracetam in Epilepsy

Prior treatment

• Current treatment with vagus nerve stimulation, deep brain and cortical stimulation for 1 year or less
• Current treatment with vigabatrin

Other illness

• Have a generalized epileptic syndrome
• Diagnosis of Lennox-Gastaut Syndrome
• Currently experiencing seizures that cannot be counted accurately
• History of any current or past nonepileptic seizures, including psychogenic seizures
• Known allergies, hypersensitivity, or intolerance to placebo, JNJ-40411813 or its excipients
• Planned epilepsy surgery within the next 6 months or completed epilepsy surgery less than (\<) 6 months ago
• History of malignancy within 5 years before screening (exceptions are squamous and basal cell carcinomas of the skin and carcinoma in situ of the cervix, or malignancy, which is considered cured with minimal risk of recurrence)
• Current or past (within the past year) major psychotic disorder, such as schizophrenia, bipolar disorder, or other psychotic conditions, recent (within the past 6 months) interictal psychosis, and major depressive disorder (MDD) with psychotic features
• Has a current or recent history of clinically significant suicidal ideation within the past 6 months, corresponding to a score of 4 (active suicidal ideation with some intent to act, without specific plan) or 5 (active suicidal ideation with specific plan and intent) for ideation on the Columbia Suicide Severity Rating Scale (C-SSRS), or a history of suicidal behavior within the past 1 year, as validated by the CSSRS at screening
• Has a history of at least mild drug or alcohol use disorder according to Diagnostic and Statistical Manual of Mental Disorders (5th edition) (DSM-5) criteria within 1 year before Screening

Other

• Exacerbation of MDD within the past 6 months; antidepressant use is allowed

• Body mass index (BMI) between 18 and 35 kilogram per meter square (kg/m\^2, inclusive (BMI = weight/height\^2). Minimum body weight should be 40-kilogram (kg)
• Established diagnosis of focal epilepsy, for at least 1 year using the International League Against Epilepsy (ILAE) criteria. Participants should not be enrolled if they are known to have had fewer than 3 or more than 100 seizures in any monthly period in the past 6 months. It is preferred that participants have experience in maintaining a seizure e-diary
• Must have had a neuroimaging procedure within 10 years, including a computed tomography (CT) scan or magnetic resonance imaging (MRI), that excluded a progressive neurologic disorder; these procedures may be performed within the 8-week baseline period
• Cohort 1: Current treatment with at least 1 and up to 4 anti-epileptic drugs (AEDs) (including levetiracetam), administered at stable dosage(s) for at least 1 month before screening, and no new AEDs added for the previous 2 months; these AEDs must remain unchanged throughout the pretreatment and double-blind treatment periods (with the exception of dosage reductions of concomitant AEDs because of suspected elevated AED levels or side effects) Cohort 2 and beyond: Current treatment with at least 1 and up to 4 AEDs (including levetiracetam or brivaracetam), administered at the appropriate dosage(s) and for a sufficient treatment period before screening. These AEDs must remain unchanged throughout the pretreatment and double-blind treatment periods (with the exception of dosage reductions of concomitant AEDs because of suspected elevated AED levels or side effects). Important note: screening of participants receiving brivaracetam will start when enrolling for Cohort 2
• Currently showing inadequate response to levetiracetam, administered at the appropriate dosage(s) and for a sufficient treatment period, based on the judgment of the investigator
• Healthy based on clinical laboratory tests, physical examination, medical history, vital signs, and 12-lead ECG
• Men or women between 18 and 69 years old