To analyze efficacy outcomes according to baseline standardized seizure frequency (SSF) quartile in order to determine whether baseline seizure burden influenced response to therapy with eslicarbazepine acetate (ESL).

Pre-existing seizure burden was variable amongst patients in a Phase IV study of ESL, as demonstrated by the higher mean than median SSF at baseline (Arm 1: 4.8 vs 2.0; Arm 2: 18.3 vs 2.4, respectively).

We report a post-hoc analysis of data from a Phase IV study of ESL taken as a first adjunctive therapy with levetiracetam or lamotrigine monotherapy, or as later adjunctive therapy following current or prior use of 1–2 antiseizure drugs, in adults with focal seizures in a real-world setting (NCT03116828). Baseline SSF values >Q3 + 1.5*interquartile range were identified as outliers. Patients were divided into quartiles according to baseline SSF, either including or excluding outliers.

Including outliers, the efficacy population comprised 44 patients in Arm 1 (ESL as first add-on) and 58 in Arm 2 (ESL as later add-on). When outliers were excluded, there were 40 patients in Arm 1 and 48 patients in Arm 2; all 14 outliers were in baseline SSF Q4. In Arm 1 Q4, 24-week retention rates were 81.8% including outliers and 85.7% excluding outliers; in Arm 2 Q4, retention rates were 64.3% and 80.0%, respectively. As efficacy outcomes were not markedly different when excluding outliers, we proceeded without excluding outliers. Overall, there was no clear relationship between baseline SSF quartile and retention rate, median change from baseline in SSF, 50% responder rate, or seizure freedom rate, in Arm 1 or Arm 2.

In this real-world open-label study, ESL was effective for the treatment of focal seizures across the range of patient baseline seizure frequencies.