A Multicentre, Open-Label, Long-Term, Safety and Tolerability Study of Retigabine Immediate Release (IR) in Adults with Partial-Onset Seizures (Extension of Study RGB113905: RTG113413).

Epilepsy affects approximately 50 million people worldwide. Currently available
antiepileptic drugs (AEDs) provide satisfactory seizure control in
approximately 70% of patients; however, the remaining 30% of epilepsy patients
are refractory to treatment. The partial-onset seizure is the most common type
of seizure that is uncontrolled in adult patients.
The introduction of new AEDs during the last decade has increased therapeutic
possibilities. However, none of the newer AEDs provides adequate seizure
control in all patients. The treatment of patients who do not respond
adequately to current AEDs remains a problem and motivates the continued search
for compounds with good efficacy and an acceptable safety and tolerability
profile.
Retigabine is a novel antiepileptic compound with well-documented
anticonvulsant properties. Retigabine has a primary pharmacological action that
is unlike currently available antiepileptic drugs (AEDs).
Retigabine has been shown to be superior to placebo as adjunctive therapy in
subjects with partial-onset epilepsy.
The RCTs involved strict selection criteria and also mandated titration to one
of three fixed doses. In these studies, in about 70% of cases, retigabine was
an add-on to two or more AEDs.
The study RGB113905 is a hypothesis generating investigation to gain insight
into efficacy, safety and tolerability, and health outcomes of retigabine as
adjunctive therapy to specified monotherapy AED treatments using a flexible
dosing regimen in adult subjects with partial-onset seizures.
Through the current follow-up study of RGB113905 (RTG113413) patients may
continu using retigabine until the EMEA has decided on the application for a
market authorisation, with a maximum study duration of 3 years.

Primary: Long-term safety and tolerability.
Secondary: Long-term efficacy.

Open-label, non-comparative phase III study:
* Continuation of final dose of retigabine and other anti-epileptics in study
RGB113905 by patients who have successfully copmleted this study.
* After 1st week possibility to change nature and/or dose of retigabine and/or
other anti-epileptics.
* Maximal study duration 3 years. Study may be discontinued earlier in case one
of the following occurs: retigabine becomes commercially available for the
treatment of epilepsy following approval by the regulatory authorities, or
approval for retigabine is not given by the regulatory authorities, or GSK
stops the study.
Approx. 140 patients.

Treatment with retigabine.

Risks: Adverse effects of study medication.
Burden: 14 visits in 3 years. All visits: vital signs, blood tests (7
ml/occasion for safety), pregnancy test (if relevant), ECG, questions about
mental condition and suicide thoughts.
Yearly: physical and neurological examination, questionnaire bladder function,
bladder ultrasound.
Diary during entire period (seizure calendar).