Exploring the Effectiveness of Adjunctive Cenobamate in Focal Epilepsy: A Time-Based Analysis

Background: A growing body of evidence supports the effectiveness of cenobamate (CNB). This study aimed to assess the clinical response to add-on CNB through a time-to-event approach and explore the potential contribution of the concomitant classes of antiseizure medications (ASMs) to improve CNB clinical use. Patients and Methods: This study is a subgroup analysis of a larger retrospective, multicenter study on adults with focal-onset seizures participating in the Italian Expanded Access Program at five pre-established centers. The primary endpoint was the time-to-baseline seizure count; secondary endpoints included the rates of seizure response, seizure freedom (defined as no seizures’ occurrence since at least the previous follow-up visit), treatment discontinuation, and adverse events (AEs). Results: Data on 92 participants were extracted, with a median age of 44 (first quartile (Q1)–third quartile (Q3): 29.25–50.75) years. The number of seizures recorded during the 90-day baseline was reached by 59/92 (64.1%) subjects during the 12-month follow-up. A higher, but not statistically significant probability of reaching the baseline seizures count was shown in the subgroups of subjects taking CNB with sodium channel blockers (SCBs) (hazard ratio [HR] 2.75; 95% confidence interval [CI] 0.79–9.61, p = 0.112) and both SCBs and GABAergics (HR 1.48; 95% CI 0.43–5.09, p = 0.536) compared with subjects taking GABAergics without SCBs. At 12 months, the rates of seizure response, seizure-freedom, and treatment discontinuation were 42.0%, 13.6%, and 23.9%, respectively. A total of 47/92 (51.1%) subjects experienced AEs (mainly somnolence, dizziness, and balance disorders) at a median time of 61 (Q1–Q3: 30–101) days. There was a higher, but not statistically significant risk of AEs occurrence in subjects treated with both SCBs and GABAergics and in those taking SCBs without GABAergics (HR 2.24; 95% CI 0.51–9.82, p = 0.286 and HR 1.40; 95% CI 0.31–6.39, p = 0.661, respectively) compared with those taking GABAergics without SCBs. The main limitations are the retrospective design and the small sample size. Conclusions: This time-to-event analysis added new insights to the currently available evidence about the real-world effectiveness of add-on CNB. Explorative estimates suggested favorable trends for subjects treated with concomitant GABAergics and without SCBs, who seemed to reach baseline seizure count and experience AEs less frequently and later than subjects treated with other concomitant ASMs. Further studies are needed to identify the best combinations of CNB with other ASMs to maximize seizure control and tolerability.