Efficacy of cenobamate by focal seizure subtypes: Post-hoc analysis of a phase 3, multicenter, open-label study

Purpose: To report post-hoc efficacy data by focal seizure subtypes from 10 US study sites from a large, global, open-label, phase 3 study of adjunctive cenobamate.Methods: Patients 18-70 years old with uncontrolled focal seizures taking stable doses of 1-3 antiseizure medications were administered increasing daily doses of cenobamate (12.5, 25, 50, 100, 150, 200 mg/day) at 2-week intervals (target dose 200 mg/day). Further increases to 400 mg/day by 50-mg/day increments every other week were allowed.Results: 240 patients were evaluated; 27 (11.3%), 224 (93.3%), and 56 (23.3%) patients had focal aware motor (FAM), focal impaired awareness (FIA), and focal to bilateral tonic-clonic (FBTC) seizures, respectively (patients may have had > 1 seizure subtype). Median baseline seizure frequencies/28 days were 10.5, 2.3, and 0.9 for FAM, FIA, and FBTC seizure subtypes. Reductions in median percent seizure frequency/28 days from baseline were observed during Months 1-3 (55.0%, 52.4%, and 94.1% for FAM, FIA, and FBTC). Greater reductions were observed during Months 4-5 (88.2%, 81.0%, and 100%) and during Months 25-27 (98.1%, 100%, and 100%). The percentage of patients achieving 100% seizure reduction in the FAM, FIA, and FBTC seizure subtypes was 22.2% (6/27), 21.5% (48/223), and 50% (28/56) during Months 1-3 and increased to 47.8% (11/23), 54.3% (88/162), and 90.5% (38/42) during Months 25-27, respectively. The most common treatment-emergent adverse events (> 20%) were fatigue, dizziness, and somnolence. No cases of DRESS were reported.Conclusions: Seizure reductions occurred in all focal seizure subtypes with cenobamate over time through Months 25-27, with the earliest onset in the FBTC group. Results from this subset analysis of the phase 3 study support the long-term efficacy of cenobamate across focal seizure types.