This study will assess the efficacy of BGG492 as adjunctive treatment in patients with refractory partial onset seizures

Inclusion Criteria:

• Outpatients ≥ 50 kg (110 lb) of weight
• A diagnosis of epilepsy (≥ 2 years prior to screening) with partial seizures with or without secondarily generalized seizures
• Uncontrolled partial seizures despite having been treated with at least two different AEDs within the last 2 years prior to screening.
• Treated with a stable dose of 1-2 AEDs
• At least 4 partial seizures during the 4-week baseline period and at least 4 partial seizures during the 4 weeks prior to the baseline period.
• No 28-day seizure-free period during the 8 weeks preceding randomization
• Positive biomarker screening

Exclusion Criteria:

• Presence of only non-motor simple partial seizures
• History of psychogenic seizures
• Absences, myoclonic seizures e.g. in the context of primary generalized epilepsy;
• Previous history of Lennox-Gastaut syndrome
• Pregnant or nursing (lactating) women
• Status epilepticus or seizure clusters, according to the judgement of the investigator, occurring within 52 weeks prior to randomization

Other protocol-defined inclusion/exclusion criteria may apply