A Double-Blind, Randomized, Placebo-Controlled, Phase 2 Trial of YKP3089 as Adjunctive Therapy in Subjects With Partial Onset Seizures

Inclusion Criteria:

- Weight at least 40 kg

- A diagnosis of partial epilepsy according to the International League Against
Epilepsy's Classification of Epileptic Seizures. Diagnosis should have been
established by clinical history and an electroencephalogram (EEG) that is consistent
with localization related epilepsy; normal interictal EEGs will be allowed provided
that the subject meets the other diagnosis criterion (ie, clinical history)

- Have uncontrolled partial seizures despite having been treated with at least 1 AED
within approximately the last 2 years

- During the 8-week baseline period, subjects must have at least 8 partial seizures
including only simple partial seizures with motor component, complex partial seizures,
or secondarily generalized seizures without a seizure-free interval of greater than 25
days any time during the 8 weeks baseline. Subjects must have at least 3 of these
partial seizures during each of the two consecutive 4-week segments of the baseline
period

- Currently on stable antiepileptic treatment regimen.

Exclusion Criteria:

- A history of nonepileptic or psychogenic seizures

- Presence of only nonmotor simple partial seizures or primary generalized epilepsies

- Presence or previous history of Lennox-Gastaut syndrome

- An active CNS infection, demyelinating disease, degenerative neurologic disease, or
any CNS disease deemed to be progressive during the course of the study that may
confound the interpretation of the study results

- Any clinically significant psychiatric illness, psychological, or behavioral problems
that, in the opinion of the Investigator, would interfere with the subject's ability
to participate in the study

- History of alcoholism, drug abuse, or drug addiction within the past 2 years

- History of status epilepticus within 3 months of Visit 1

- A "yes" answer to Question 1 or 2 of the C-SSRS (Baseline/Screening version) Ideation
Section in the past 6 months or a "yes" answer to any of the Suicidal Behavior
Questions in the past 2 years

- More than 1 lifetime suicide attempt

- Participation in any other trials involving an investigational product or device
within 30 days of screening (or longer, as required by local regulations)

- A history of any previous exposure to YKP3089