Assessment of the long-term efficacy and safety of adjunctive perampanel in adolescent patients with epilepsy: Post hoc analysis of open-label extension studies

Objective: This post hoc analysis of four open-label extension (OLEx) studies evaluated the long-term efficacy and safety of adjunctive perampanel in adolescent patients (aged 12 to <= 17 years) with focal-onset seizures (FOS), with/without focal to bilateral tonic-clonic seizures (FBTCS), or generalized tonic-clonic seizures (GTCS). Methods: Patients who completed one of six double-blind, placebo-controlled studies could enter one of four OLEx studies comprising a blinded Conversion Period (6-16 weeks) followed by a Maintenance Phase (27 to <= 256 weeks; perampanel dose: <= 12 mg/day). Exposure, retention, seizure outcomes, and treatment-emergent adverse events (TEAEs) were analyzed. Efficacy outcomes were analyzed using observed case and last observation carried forward (LOCF) approaches; the latter was used to account for early dropouts. Results: The Full Analysis Set comprised 309 adolescents with FOS (FBTCS, n = 109) and 19 with GTCS, and the Safety Analysis Set comprised 311 with FOS (FBTCS, n = 110) and 19 with GTCS. Mean (standard deviation) cumulative duration of perampanel exposure (weeks) was: FOS, 77.7 (58.7); FBTCS, 88.7 (63.8); and GTCS, 97.0 (35.5). Retention rates were maintained for <= 2 years (FOS, 50.0 %; FBTCS, 57.1 %; GTCS, 41.7 %). Seizure control (median percent reduction in seizure frequency/28 days) was sustained for up to 2 years; FOS (59.4 %, n = 113), FBTCS (64.6 %, n = 53), and GTCS (86.5 %, n = 17). At Year 2, 50 % responder rates were: FOS, 58.4 % (n = 66); FBTCS, 54.7 % (n = 29); and GTCS, 82.4 % (n = 14); seizure-freedom rates were: FOS, 5.3 % (n = 6); FBTCS, 24.5 % (n = 13); and GTCS, 35.3 % (n = 6). Long-term seizure control was observed even in LOCF analyses. The incidence of TEAEs was highest during Year 1 (FOS, n = 269 [86.5 %]; FBTCS, n = 95 [86.4 %]; GTCS, n = 15 [78.9 %]), compared with Years 2-4; the most common (>= 10 % of patients) were dizziness, somnolence, and nasopharyngitis. No new safety signals emerged with long-term treatment.Conclusions: This post hoc analysis suggests that long-term (<= 2 years) adjunctive perampanel (<= 12 mg/day) is efficacious and generally well tolerated in adolescent patients with FOS, with or without FBTCS, or GTCS.