Conditions: Epilepsy
Keywords: Retigabine Drug-Resistant Epilepsy Partial-Onset Seizures Safety and Tolerability Immediate Release Long-Term Adjunctive Therapy Asian Subjects Efficacy GW582892
Allocation: NA | Intervention model: SINGLE_GROUP
Enrollment: 30
Healthy volunteers: no

Brief summary:
This is a multicentre, long-term, open-label extension (OLE) study to assess the long-term safety, tolerability and efficacy of retigabine immediate-release (IR) as adjunctive therapy in adult Asian subjects with drug-resistant partial-onset seizures (POS).

Detailed description:
Subjects who successfully complete the Maintenance Phase of Study RTG114855 (parent study) and are expected to benefit from therapy with retigabine IR will be eligible for this OLE study. The study will consist of Screening (1 day), Open-Label Treatment and Follow-up (3 weeks) phase. Subjects will initially receive a starting dose of retigabine IR at 900 milligram (mg)/day and the same concurrent antiepileptic drug (AED) regimen that they were receiving at the final visit of the Transition Phase of the parent study. After the first week of the OLE study, the dose of retigabine IR may be adjusted to between 600 and 1200 mg/day, with dose adjustments in increments or decrements of 150 mg/week, based on efficacy and tolerability. In addition, the dose and number of concurrent AEDs may also be adjusted to meet each individual subject's needs. The efficacy and safety issues will be assessed throughout the study; subjects will be instructed to call the investigator if they experience any efficacy or tolerability issues between the study visits. As the duration of the study will be determined based on the following four conditions: 1) regulatory approval and commercialisation of retigabine IR; 2) retigabine IR is not approved by the regulatory authorities; 3) the study is terminated by the Sponsor for reasons including, but not limited to, safety issues; or 4) the subject is withdrawn or withdraws consent, 4 years will be considered as a guide to the duration of the study. The safety and tolerability endpoints are incidence and severity of adverse events (AEs); proportion of subjects with AEs leading to discontinuation; change from Baseline in vital sign measurements and weight; change from Baseline in electrocardiogram parameters; change from Baseline in haematology, chemistry, and urinalysis parameters; changes from Baseline in American Urological Association Symptom Index and post-void residual bladder ultrasound volumes; and summary of the Columbia-Suicide Severity Rating Scale. Efficacy will be assessed by calculating the percent change from Baseline (parent study) in 28-day total POS frequency for the entire open-label Treatment Phase of this OLE study. This will also be calculated based on duration of exposure. Responder rate (defined as a \>/=50% reduction from Baseline in 28-day total POS frequency) will also be summarised for the entire open-label Treatment Phase and by duration of exposure.

Arms:
arm 1: All subjects will initially receive a starting dose of retigabine IR at 900 mg/day and after the first week of the OLE study, the dose of retigabine IR may be increased or decreased in increments or decrements of decrements of 150 mg/day on weekly basis based on efficacy and tolerability. The overall daily dose of retigabine IR must be maintained between a minimum dose of 600 mg/day and a maximum dose of 1200 mg/day.

Interventions: intervention 1: Retigabine IR
Intervention descriptions: intervention 1: Retigabine IR tablets will be available in 5 strengths: 50 mg, 100 mg, 200 mg, 300 mg, and 400 mg.

Protocol document: