Objective: Evaluate long-term efficacy (percent seizure frequency reduction and responder rates), safety, and tolerability of adjunctive cenobamate in an open-label extension (OLE) of the randomized, double-blind, placebo-controlled study.
Methods: Patients (aged 18-70 years) with uncontrolled focal seizures despite treatment with 1-3 antiseizure medications who completed the 18-week double-blind study (n=360) could enter the OLE, where they underwent a 2-week blinded conversion to cenobamate (target dose, 300 mg/day; min/max, 50/400 mg/day).
Results: Three hundred fifty-five patients were included in the OLE safety population (265 originally randomized to cenobamate, 90 originally randomized to placebo), and 354 were included in the OLE modified intent-to-treat population. As of July 2019, 58.9% (209/355) of patients were continuing cenobamate treatment and 141 had discontinued, including 16.6% (59/355) due to lack of efficacy, 8.7% (31/355) due to withdrawal by patient, and 7.6% (27/355) due to adverse events. Median (range) duration of OLE exposure was 53.9 (1.1-68.7) months. Retention rates at 12, 24, 36, and 48 months were 83%, 71%, 65%, and 62%, respectively. Median percent seizure frequency reduction over baseline increased with each 6-month OLE interval, up to 76.1% at months 43-48. Among observed patients, 16.4% (36/220) achieved 100% and 39.1% (86/220) achieved ≥90% seizure reduction during >36-48 months. Among the initial OLE mITT population, 10.2% (36/354) of patients achieved 100% and 24.3% (86/354) achieved ≥90% seizure reduction during >36-48 months. Similar to the double-blind study, adverse events (AEs) included dizziness, somnolence, fatigue, and headache. Serious AEs occurred in 20.3% (72/355) of patients.
Conclusion: Long-term efficacy, including 100% and ≥90% seizure reduction, was sustained during 48 months of cenobamate treatment, with 71% retention at 24 months. No new safety issues were identified. These results confirm the findings of the double-blind study and support the potential long-term clinical benefit of cenobamate.
Registration: ClinicalTrials.gov NCT01866111.
Classification of evidence: This study provides Class IV evidence that oral Cenobamate 50-400 mg/day is effective as an adjunctive treatment for the long-term management of patients with uncontrolled focal seizures previously treated with 1 to 3 ASMs.
Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.