An Open Label Study to Evaluate the Effects of Ezogabine/Retigabine Added to Existing Anti-epileptic Drug(s) on Urinary Voiding Function in Subjects With Partial Onset Seizures

Inclusion Criteria:

- Is ≥18 years of age (male or female).

- Has a confident diagnosis of epilepsy with partial onset seizures with or without
secondary generalization (classified according to International League Against
Epilepsy (ILAE) Guidelines, 1981) ≥ 2 years.

- Is currently being treated with a stable regimen of one to three AEDs during the 4
weeks prior to the Screening Visit.

- Following Amendment 03: must be considered drug resistant, consistent with the
definition proposed by Kwan, et al 2010 [Kwan].

- Note: Vagus Nerve Stimulator (VNS), VNS will not be counted as a concurrent AED.
Subjects with surgically implanted VNS will be allowed to enter the study provided
that all of the following conditions are met:

- The VNS has been in place for at least 24 weeks prior to the Screening Visit

- The settings must remain the same for at least 4 weeks prior to the Screening Visit
and throughout the study

- The battery is expected to last for the duration of the study

- Subject who are considering implantation of a VNS are excluded from participating in
this study

- Note: The chronic use of benzodiazepines as a concurrent AED is permitted as long as
the dose is kept constant for at least 4 weeks before the Screen Visit and throughout
the study.

- Is able and willing to maintain an accurate and complete a two (2) day Voiding Diary
at protocol specified time points.

- Is able and willing to maintain an accurate and complete daily written Seizure
Calendar at specified time points or has a caregiver who is able and willing to
maintain an accurate and complete daily written Seizure Calendar for the entire
duration of the study.

- Has given written informed consent, prior to the performance of any study assessments.

- A female subject is eligible to enter and participate in the study if she is not
pregnant or lactating or planning to become pregnant during the study and is of:

- Non-childbearing potential (i.e., physiologically incapable of becoming pregnant,
including any female who is pre-menarchal or post-menopausal).

- Pre-menopausal females with a documented (medical report verification) hysterectomy
with or without oophorectomy or bi-lateral oophorectomy when reproductive status has
been confirmed by hormone level assessment

- Post-menopausal females defined as being amenorrhoeic for greater than one year with
an appropriate clinical profile (e.g., age appropriate, history of vasomotor
symptoms). However, if indicated, this should be confirmed by oestradiol and follicle
stimulating hormone (FSH) levels consistent with menopause (according to local
laboratory ranges).

- Women who have not been confirmed as post-menopausal should be advised to use
contraception as outlined in Appendix 2.

- Child-bearing potential, has a negative pregnancy test at screening and baseline, and
agrees to satisfy one of the requirements in as listed in Appendix 2.

- Liver function tests: aspartate aminotransferase (AST) and alanine aminotransferase
(ALT) <2 x upper limit of normal (ULN); alkaline phosphatase and bilirubin less than
or equal to 1.5 x ULN (isolated bilirubin >1.5 x ULN is acceptable if bilirubin is
fractionated and direct bilirubin <35%).

- Has a normal creatinine clearance (age corrected) as calculated with the
Cockcroft-Gault formula.

Exclusion Criteria:

- Has generalized epilepsy (e.g., Lennox-Gastaut, Juvenile Myoclonic epilepsy, Absence,
etc).

- Has had status epilepticus (other than simple partial status epilepticus) within the
12 months prior to Screening or during the Baseline Phase.

- Has a history of innumerable seizures within the 12 months prior to Screening where
the individual seizures cannot be counted.

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

- Acute Urinary Retention (treated or untreated) within 6 months of screening or an
episode of Acute Urinary Retention (treated) within the last two years with symptoms
within the last 6 months.

- Screening AUA SI Score >7 (>11 for subject over 55 years old).

- Flowmetry Peak Flow < 15mL/sec out of a urine volume void of 150mL (<11 mL/sec for
subject over 55 years old) at Screening.

- PVR >125mL or >40% functional residual volume at Screening.

- Prior history of administration of Botox® within genitourinary system.

- Prior history or any type of medical or surgical therapy for urinary incontinence.

- Prior history of treated or untreated, bladder, prostate, uterine or cervical cancer.

- Use of sildenafil, tadalafil, vardenafil or other PDE-5 inhibitors within 2 weeks of
study start.

- Use of α-adrenoreceptor antagonists within 2 weeks of study start.

- Has had previous exposure to ezogabine/retigabine.

- Is currently or has been abusing substance(s) or any medications in the 12 months
prior to Screening.

- Has taken an investigational drug, or used an investigational device, within the
previous 4 weeks prior to Screening or plans to take another investigational drug
anytime during the study.

- Is currently following or planning to follow the ketogenic diet.

- Has been treated with felbamate or vigabatrin within the past 6 months prior to
Screening; if a subject has been previously treated with vigabatrin, a visual
perimetry test prior to screening (or within the past 6 months) must show normal
visual fields or no worsening of recognized visual field abnormalities as compared
with prior to vigabatrin treatment.

- Use of CNS-active medication (other than concomitant AED therapy), unless subjects had
been stabilized on such medication for more than 4 weeks prior to Screening.

- Use of herbal treatments with CNS activity within 4 weeks prior to Screening.

- Current use of any prohibited concomitant medication as indicated in Section 5.7.2.

- Is planning surgery to control seizures during the study.

- Is suffering from acute or progressive neurological disease, severe psychiatric
disease, or severe mental abnormalities that, in the investigator's judgment, are
likely to interfere with the objectives of the study.

- Has 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.

- Has an average QTc ≥ 450 msec or ≥ 480 msec for subjects with Bundle Branch Block at
the time of Screening.

Note: If the initial electrocardiogram (ECG) at Screening indicates a corrected QT (QTc)
interval outside these limits, two further ECGs should be performed and the average QTc
value of these triplicate ECGs calculated. If the average value exceeds the stated limits,
the subject is not eligible.

- Has active suicidal plan/intent or has had active suicidal thoughts in the past 6
months. Has history of suicide attempt in the last 2 years or more than one lifetime
suicide attempt.

- Has positive test results for hepatitis B surface antigen, positive hepatitis C virus,
or human immunodeficiency virus (HIV)-1 or -2 at Screening.