This was a phase III 4-part study in multiple centres. Part I was a 26-week parallel-group, randomised, placebo-controlled period (8 weeks single-blind placebo baseline, 2 weeks double-blind titration, 12 weeks maintenance, and 4 weeks tapering off). After completing the baseline period, patients were randomised in a 1:1:1:1 ratio to 1 of 3 ESL dose levels or to placebo. Part II was a 1-year open-label extension for patients who had completed Part I. The starting dose was 800 mg once daily and could be titrated up or down at 400-mg intervals between 400 and 1200 mg. Part III was an additional 1-year open-label extension for patients who had completed Part II, had participated in the post-Part II study extension, which allowed patients to continue treatment with ESL, or had continued to take ESL in a compassionate use program. ESL starting doses were the same as received at the end of Part II, during post-Part II study extension, or under compassionate use, and could be titrated up or down at 400-mg intervals between 400 and 1200 mg once daily. Part IV was a study extension to allow patients to continue ESL treatment after the end of Part III until marketing authorisation or discontinuation of clinical development.

Duration of Treatment: The duration of Part I was 26 weeks: 8 weeks of placebo run-in, 2 weeks of dose titration, 12 weeks of maintenance, and 4 weeks of tapering-off period. The duration of Part II was 1 year. The duration of Part III was planned to be 1 year (some patients were treated for >1 year). The duration of Part IV was >3 years (patients could continue treatment with ESL until market availability).

Inclusion Criteria:

• written informed consent signed by patient
• aged 18 years or more
• documented diagnosis of simple or complex partial seizures with or without secondary generalisation since at least 12 months prior to screening
• at least 4 partial seizures in each 4 week period during the last 8 weeks prior to screening, currently treated with 1 or 2 AEDs (any except oxcarbazepine and felbamate), in a stable dose regimen during at least 2 months prior to screening (patients using vigabatrin should have been on this medication for at least 1 year with no deficit in visual field identified)
• excepting epilepsy, patient is judged to be in general good health based on medical history, physical examination and laboratory tests
• post-menopausal or otherwise incapable of becoming pregnant by reason of surgery or tubal ligation; in case of woman of childbearing potential, patient must present a serum beta-hCG test consistent with a non-gravid state and agree to remain abstinent or use reliable contraception (oral contraception should be combined with a barrier method)

Exclusion Criteria:

• only simple partial seizures with no motor symptomatology (classified as A2-4 according to the International Classification of Epileptic Seizures) that are not video-EEG documented
• primarily generalised epilepsy
• known rapid progressive neurological disorder; history of status epilepticus or cluster seizures (i.e., 3 or more seizures within 30 minutes) within the 3 months prior to screening
• seizures of psychogenic origin within the last 2 years
• history of schizophrenia or suicide attempt
• currently on or with exposure to felbamate or oxcarbazepine more within one month of screening
• using benzodiazepines on more than on an occasional basis (except when used chronically as AED)
• previous use of ESL or participation in a clinical study with ESL
• known hypersensitivity to carbamazepine, oxcarbazepine or chemically related substances
• history of abuse of alcohol, drugs or medications within the last 2 years
• uncontrolled cardiac, renal, hepatic, endocrine, gastrointestinal, metabolic, haematological or oncology disorder
• second or third-degree atrioventricular blockade not corrected with a pacemaker
• relevant clinical laboratory abnormalities

26-week

Safety endpoints included Adverse events (AEs), clinical laboratory tests (haematology, coagulation, biochemistry, thyroid function, and urinalysis), vital signs and weight, electrocardiogram, and blood trough levels of concomitant Anti-epileptic drug (AEDs).