Efficacy and safety of perampanel in patients with drug-resistant partial seizures after conversion from double-blind placebo to open-label perampanel

OBJECTIVE To evaluate the efficacy and safety of perampanel in patients with drug-resistant partial seizures after the conversion from double-blind placebo in three phase III studies to open-label perampanel, and to assess the impact of perampanel titration rates through a comparison of weekly vs biweekly dose increases. METHODS Patients who completed the three multinational, double-blind, placebo-controlled, phase III core studies (studies 304, 305, or 306) were eligible to enroll in the extension study (study 307). Patients completing the double-blind treatment (6-week titration, 13-week maintenance) with placebo (DB-PBO) or perampanel (DB-PER) began the extension study with a 16-week blinded conversion period, during which DB-PBO patients were switched to perampanel. Doses were titrated in 2-mg increments (biweekly) to an individualized maximum tolerated dose of perampanel (up to 12 mg/day). Patients then entered a planned, open-label treatment period. RESULTS Perampanel treatment during the extension study reduced total seizure frequency/28 days relative to the double-blind prerandomization baseline regardless of prior perampanel or placebo treatment in the core studies. In the DB-PBO patients, median percent reductions in seizure frequency at the end of the double-blind period, at the end of the conversion period, and at Weeks 40-52 in the open-label maintenance period were 18.6%, 44.3%, and 55.0%, respectively. Seizure control was also improved in the DB-PER patients during the extension period compared to the end of the double-blind period. Responder rates were similar between the 2 patient groups at the end of the conversion period. Perampanel was well tolerated, with the most common treatment-emergent adverse events being dizziness, somnolence, weight increase, irritability, fatigue, and headache. For those patients randomized to the 12 mg group (DB-PER 12 mg), 78.4% reached the daily dose of 10 or 12 mg by the end of the 6-week titration period of the double-blind phase. By the end of the 16-week conversion period of the extension study, 64.0% of DB-PBO patients reached the daily dose of 10 or 12 mg. Seizure frequency reduction was greater after the first 13-week maintenance period of the extension study in the DB-PBO group compared to patients assigned to DB-PER 12mg during the 13-week maintenance period of the double-blind study. CONCLUSION Patients who received placebo in the phase III core DB studies and transitioned to perampanel in the open-label extension study (DB-PBO) achieved seizure control at the end of the conversion period similar to that of patients who had been previously exposed to perampanel (DB-PER) as well as comparable safety outcomes. Patients who received perampanel during the core studies and continued with treatment during the extension study (DB-PER) also showed sustained improvements in seizure control with long-term exposure to perampanel.