A Phase 2A, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety and Pharmacokinetics of ES-481 in Adult Patients with Drug Resistant Epilepsy.

ES-481 will be administered as 25 mg oral gelatin capsules. The starting dose, dose administration schedule and the number of capsules of study medication (ES-481 or Placebo) to be administered per week in each 28-day treatment periods (Periods 1 and 2) are shown on the table below. Week 1: 25 mg daily: 1 x 25 mg gelatin capsule Days 1 to 7 in Treatment Period 1 and Days 43 to 49 in Treatment Period 2 Week 2: 25 mg twice a day: 2 x 25 mg gelatin capsules Days 8 to 14 in Treatment Period 1 and Days 50 to 56 in Treatment Period 2 Week 3: 50 mg twice a day: 4 x 25 mg gelatin capsules Days 15 to 21 in Treatment Period 1 and Days 57 to 63 in Treatment Period 2 Week 4: 75 mg twice a day: 6 x 25 mg gelatin capsules Days 22 to 28 in Treatment Period 1 and Days 64 to 70 in Treatment Period 2 In the 14-day step-down and washout period (following the two Treatment Periods), subjects will be washout of the medication as follows: Day 1: 125 mg: 3 x 25 mg capsules in the morning and 2 x 25 mg capsules in the evening. Day 2: 100 mg: 2 x 25 mg capsules in the morning and 2 x 25 mg capsules in the evening. Day 3: 75 mg: 2 x 25 mg capsules in the morning and 1 x 25 mg capsules in the evening. Day 4: 50 mg: 1 x 25 mg capsules in the morning and 1 x 25 mg capsules in the evening. Day 5:50 mg: 1 x 25 mg capsules in the morning and 1 x 25 mg capsules in the evening. Day 6: 25 mg: 1 x 25 mg gelatin capsule in the morning. Day 7: 25 mg: 1 x 25 mg gelatin capsule in the morning. Days 8 – 14: 0 mg: 7-day washout period. Drug accountability will be performed on a weekly basis. A 36-week open-label extension for subjects who successfully completed both treatment periods and in the opinion of the Principal Investigator demonstrated efficacy to study drug will be treated with maximum dose of 75 mg bid of ES-481