Inclusion Criteria:  Age 18-70 Focal epilepsy uncontrolled in spite of past or present treatment with four or more anti-seizure drugs (ASDs), with focal aware motor seizures, focal unaware seizures and focal to bilateral tonic clonic seizures. Stable ASD doses for at least 30 days Epilepsy duration for ≥ 2 years Past/current treatment with ≥ 4 ASDs. VNS, RNS and DBS treatment will be allowed and will not count as an ASD. VNS, RNS and DBS setting must be stable for 3 months prior to enrollment. Seizure frequency of ≥1/month for ≥ 10/12 months before treatment initiation  Exclusion Criteria:  Primary generalized epilepsy Focal aware non-motor seizures without bilateral tonic-clonic seizures Non-epileptic seizures Progressive neurological disease including neoplasm, CNS degenerative disorders including Alzheimer's disease Any systemic illness or unstable medical condition that might pose additional risk, including renal or liver disease, clinically uncontrolled cardiac disease other unstable metabolic or endocrine disturbances, and active systemic cancer Change in the dose of any ASD within 30 days prior to enrollment Active drug or alcohol dependence or any other factors that, in the opinion of the site investigators would interfere with adherence to study requirements Pregnancy Use of any CNS-active investigational drugs within 1 month of enrollment Resective epilepsy surgery less than 6 months before study initiation Vagal nerve stimulator VNS, RNS or DBS implantation less than 6 months before study initiation Adjustment of VNS, RNS or DBS settings less than 3 months before study initiation Inability or unwillingness of subject or legal guardian/representative to give written informed consent.