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

Purpose: 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. Methods: 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. Key Findings: 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 (1.1128.1) 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 1426 (n = 1,114), -46.5% for weeks 4052 (n = 731), and -58.1% for weeks 92104 (n = 59). Overall responder rates in patients included in each 13-week interval of perampanel treatment were 41.4% for weeks 1426 (n = 1,114), 46.9% for weeks 4052 (n = 731), and 62.7% for weeks 92104 (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). Significance: 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.