Perampanel, a selective, noncompetitive α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor antagonist, as adjunctive therapy for refractory partial‐onset seizures: Interim results from phase III, extension study 307

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To evaluate safety, tolerability, and seizure outcome data during long-term treatment with once-daily adjunctive perampanel (up to 12 mg/day) in patients with refractory partial-onset seizures. Study 307 was an extension study for patients completing the double-blind phase of three pivotal phase III trials (studies 304, 305, and 306). The study consisted of two phases: an open-label treatment phase (including a 16-week blinded conversion period and a planned 256-week maintenance period) and a 4-week follow-up phase. Patients were blindly titrated during the conversion period to their individual maximum tolerated dose (maximum 12 mg/day). Adverse events (AEs) were monitored throughout the study and seizure frequency recorded. The interim data cutoff date for analyses was December 1, 2010. In total, 1,218 patients were enrolled in the study. At the interim cutoff date, 1,186 patients were in the safety analysis set; 1,089 (91.8%) patients had >16 weeks of exposure to perampanel, 580 (48.9%) patients had >1 year of exposure, and 19 (1.6%) patients had >2 years of exposure. At the interim analysis, 840 (70.8%) patients remained on perampanel treatment. The large majority of patients (n = 1,084 [91%]) were titrated to 10 mg or 12 mg/day. Median (range) duration of exposure was 51.4 (1.1-128.1) weeks. Treatment-emergent AEs were reported in 87.4% of patients. The most frequent were dizziness (43.9%), somnolence (20.2%), headache (16.7%), and fatigue (12.1%). Serious AEs were reported in 13.2% of patients. In the intent-to-treat analysis set (n = 1,207), the frequency of all seizures decreased over the first 26 weeks of perampanel treatment in patients with at least 26 weeks of exposure to perampanel (n = 1,006 [83.3%]); this reduction was maintained in patients with at least 1 year of exposure (n = 588 [48.7%]). The overall median percent changes in seizure frequency in patients included in each 13-week interval of perampanel treatment were -39.2% for weeks 14-26 (n = 1,114), -46.5% for weeks 40-52 (n = 731), and -58.1% for weeks 92-104 (n = 59). Overall responder rates in patients included in each 13-week interval of perampanel treatment were 41.4% for weeks 14-26 (n = 1,114), 46.9% for weeks 40-52 (n = 731), and 62.7% for weeks 92-104 (n = 59). During the blinded conversion period, the reduction in seizure frequency in patients previously randomized to placebo (-42.4%, n = 369) was similar to that in patients previously randomized to perampanel (-41.5%, n = 817). Consistent with pivotal phase III trials, these interim results demonstrated that perampanel had a favorable tolerability profile in patients with refractory partial-onset seizures over the longer term. The decrease in seizure frequency was consistent and maintained in those patients over at least 1 year of perampanel exposure.