Dose-Optimization, Adjunctive Treatment Study of Ezogabine/Retigabine Immediate Release in Partial-onset Seizures

Inclusion Criteria:

- A male or female of 18 years of age or above capable of giving written informed
consent

- Have a confident diagnosis of epilepsy for >=6 months with partial-onset seizures
(POS), i.e., simple or complex POS with or without secondary generalization
(classified according to the International League Against Epilepsy (ILAE) Guidelines,
prior to the Screening Visit

- Currently receiving monotherapy treatment with an antiepileptic drug (AED) at a stable
dose for at least 28 days prior to the screening visit (Visit 1). If the subject is
taking a barbiturate (e.g., phenobarbital), the dose must be stable for ≥3 months
prior to the Screening Visit. Note: Subjects who have received previous adjunctive
treatment but are currently taking one AED are eligible for enrolment.

- Investigator-confirmed partial seizure frequency rate of ≥3 partial seizures per 28
days over the 8 weeks preceding the screening visit and must not have been
seizure-free for ≥ 21 consecutive days.

- Female of non-child bearing potential, or female of child-bearing potential willing to
use protocol-specified methods of contraception to prevent pregnancy during the study.

- Capable to comply with dosing of study drug, background AED, all study procedures and
to maintain an accurate and complete daily written Seizure Calendar and Functional
Status Diary

Exclusion Criteria:

- Have generalized epilepsy (e.g. Lennox-Gastaut, Juvenile Myoclonic epilepsy, Absence,
etc.) or non-epileptic seizures.

- Have had innumerable seizures within the 12-month period prior to the Screening Visit
where the individual seizures cannot be counted.

- Have had status epilepticus within 12 months prior to screening

- Have a history of pseudo seizures, non-epileptic events or any other type of
psychogenic seizures that could be confused with seizures.

- Have been treated with felbamate or vigabatrin within the 6 months prior to Screening.
If a subject has been previously treated with vigabatrin >6 months prior to Screening,
a visual perimetry test performed within 6 months prior to Screening must show normal
visual fields or no worsening of recognized visual field abnormalities as compared
with prior to vigabatrin treatment

- Benzodiazepines used in any manner other than acute usage as defined in this protocol
will be considered concurrent AED usage and will not be permitted

- Are using Central Nervous System (CNS)-active medication (other than concomitant
AED therapy), unless the subject has been stabilized on such medication for at
least 1 month prior to the Screening Visit.

- Are using herbal treatments with CNS activity within at least 1 month prior to the
Screening Visit

- Have received ezogabine/retigabine in a previous study or have taken POTIGA or
TROBALT.

- Are currently following or planning to follow the ketogenic diet

- Have an active Vagus Nerve Stimulator (VNS) to control seizures

- Are planning surgery to control seizures during the study

- Have impaired renal function as judged by a creatinine clearance of <50 mL/min

- Have a history of urinary retention or risk factors for urinary retention that in the
investigator's judgment could potentially affect subject safety.

- Have an average corrected QT interval (QTc), using Bazett's QT correction (QTcB),
≥450msec or ≥480msec for subjects with bundle branch block at the time of the
Screening Visit

- Liver function tests: alanine aminotransferase (ALT) is ≥2 times the upper limit of
normal (ULN); alkaline phosphatase and bilirubin are >1.5 × ULN (isolated bilirubin
>1.5 × ULN is acceptable if bilirubin is fractionated and direct bilirubin is <35%).

- Are suffering from acute or progressive neurological disease, severe psychiatric
disease, or severe mental abnormalities that are likely to interfere with the
objectives of the study

- Have a history of malignancy within the past 2 years; with the exception of basal cell
carcinoma

- Have unstable liver disease [chronic stable hepatitis B and C are acceptable if
subject otherwise meets entry criteria; chronic stable Hepatitis B to be excluded if
significant immunosuppressive agents administered due to risk of hepatitis B
reactivation]

- Have any medical condition that, in the investigator's judgment, is considered to be
clinically significant and could potentially affect subject safety or study outcome,
including but not limited to: clinically significant cardiac, renal, hepatic
condition, or a condition that affects the absorption, distribution, metabolism or
excretion of drugs

- Have an active suicidal plan/intent or have had active suicidal thoughts in the past 6
months. Have history of suicide attempt in the last 2 years or more than 1 lifetime
suicide attempt.

- Have a history of substance abuse (alcohol or drugs) or substance dependence within 12
months prior to screening

- Have a known hypersensitivity to any components of the study medication

- Have taken an investigational drug, or used an investigational device, within the
previous 30 days prior to screening or plans to take an investigational drug anytime
during the study.