Long-Term Safety Study of Retigabine Immediate Release (IR) as Adjunctive Therapy in the Treatment of Adults With Partial-Onset Seizures (POS)

Inclusion Criteria

• The subject has successfully completed the 20-weeks (4-weeks Titration and 16-weeks of Flexible Dose Evaluation Phases) of treatment with retigabine IR as adjunctive therapy to one of the pre-specified AEDs in the parent study RGB113905.
• The investigator and the subject, or caregiver, if applicable, should consider it beneficial for the subject to receive continued retigabine IR therapy.
• The subject is able and willing to maintain an accurate and complete daily written Seizure Calendar 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.
• The subject has given written informed consent, or has a legally authorized representative who 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 of non-childbearing potential (i.e., physiologically incapable of becoming pregnant, including any female who is pre- menarcheal or post menopausal).
• A female subject is eligible to enter and participate in the study if she is child-bearing potential and has a negative pregnancy test at Screening, and agrees to use one of the contraceptive methods listed in Appendix 3 of the protocol.
• A female subject is eligible to enter and participate in the study if she not pregnant or lactating or planning to become pregnant during the study.
• French subjects only: In France, a subject will be eligible for inclusion in this study only if either affiliated to or a beneficiary of a social security category.

Exclusion Criteria

• Has met any of the withdrawal criteria in the previous RGB113905 study or has clinically significant abnormal clinical laboratory or ECG findings not resolved prior to entry to the open-label extension study.
• Is suffering from acute or progressive neurological disease, severe psychiatric disease, or severe mental abnormalities that are likely to interfere with the study objectives.
• 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 any abnormality on 12-lead ECG at Screening which is clinically significant in the opinion of the investigator, or has QTc (either QTcB Bazett's correction or QTcF Fridericia's correction) >500 msec or >530 msec for subjects with Bundle Branch Block or an increase in QTc of >60 msec from Baseline in the parent study.
• Is unwilling or inability to follow the study procedures or reporting of AEs.
• Is planning on following a ketogenic diet or planning surgery or implantation of a Vagus Nerve Stimulator (VNS) to control seizures during the study. Note: Subjects who already have a VNS implanted which is functional may be permitted to enter the study.
• 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 1 lifetime suicide attempt.