Abstract
OBJECTIVE: We determined retention on open-label cenobamate therapy in the clinical development program to assess the long-term efficacy and tolerability of adjunctive cenobamate in individuals with uncontrolled focal seizures. METHODS: Data from two randomized, controlled cenobamate studies and one open-label safety and pharmacokinetic study were pooled. Based on the percentage of participants remaining on treatment, retention rates were estimated using Kaplan-Meier survival analyses. We performed two additional analyses to assess factors contributing to retention, stratifying a robust data set (through 2 years) by cenobamate modal dose and frequently used concomitant anti-seizure medications. Cenobamate discontinuations and treatment-emergent adverse events were summarized. RESULTS: Data from 1844 participants were pooled: 149 from a single-dose randomized trial, 355 from a multi-dose randomized trial, and 1340 from an open-label safety and pharmacokinetic study. Most participants from randomized trials continued in open-label extensions, and pooled data represent >95% of participants exposed to cenobamate. Baseline characteristics and disease and treatment histories were similar across studies. Median duration of cenobamate exposure was 34 months, with a median modal dose of 200 mg/day. Kaplan-Meier estimates of cumulative cenobamate retention rates were 80% at 1 year and 72% at 2 years. Once participants reached the maintenance phase, retention rates were consistently high in participants receiving ≥100 mg/day cenobamate, and concomitant anti-seizure medications did not affect long-term retention. By 2 years, 535 (29%) had actually discontinued cenobamate; the most common reasons for discontinuation were adverse events (37.6%), withdrawal of consent (21.1%), and other (16.8%). SIGNIFICANCE: Treatment retention rates provide a proxy measure for long-term efficacy, safety, tolerability, and adherence. The consistently high retention rates we found suggest that cenobamate may be an effective and well-tolerated new treatment option for people with drug-resistant focal seizures.