Japanese Post Marketing Study Shows Long-Term Efficacy of Stiripentol in Dravet Syndrome

Findings from a newly presented analysis of a post marketing surveillance study in Japan showed that stiripentol (Diacomit; Biocodex) demonstrated sustained long-term efficacy in reducing multiple seizure types and status epilepticus in patients with Dravet syndrome (DS) over 3 years, with an acceptable safety and tolerability profile. The findings indicated that earlier initiation of stiripentol may be associated with greater clinical benefit and improved tolerability, underscoring the potential importance of prompt therapeutic intervention in DS.¹

Among 520 patients with DS, including 131 patients younger than 3 years and 100 patients aged 19 years or older at treatment initiation, efficacy data were only available for 480 patients in the study. Across the 156-week period, researchers observed that stiripentol was associated with a median seizure frequency reduction of 64% for convulsive seizures and 100% for generalized myoclonic seizures, generalized atypical absence seizures, and focal impaired awareness seizures. Additionally, the incidence of status epilepticus decreased from 31.5% at baseline to 7.1% at 3 years.

This analysis, conducted by Laurent Chancharme, PharmD, PhD, scientific advisor at Biocodex, and colleagues, aimed to further evaluate the long-term safety and efficacy of stiripentol. Presented at the 2025 American Epilepsy Society (AES) Annual Meeting, held December 5-9, in Atlanta, Georgia, the study included all patients (mean age, 10.5 years; range, 0–50 years) who initiated stiripentol in Japan between November 2012 and August 2017, followed for up to 156 weeks. Caregivers recorded seizure frequency in diaries reviewed by treating physicians, and the incidence of status epilepticus was documented.

READ MORE: Dravet Syndrome Medication Stiripentol Effective in Real World Settings Across Various Patient Profiles

All told, efficacy was assessed using physician-rated overall improvement on a 5-point scale, and percentage reductions in seizure frequency were calculated for convulsive, myoclonic, atypical absence, and focal impaired awareness seizures. In addition, safety was evaluated by the frequency and severity of adverse drug reactions (ADRs). Subgroup analyses were then conducted to examine efficacy and safety outcomes according to age at stiripentol initiation.

Across age groups, researchers reported that the highest clinical response was observed in patients younger than 3 years, among whom 26% achieved freedom from generalized tonic-clonic (GTC) seizures by the end of the treatment period. Adults aged at least 19 years demonstrated a lower response rate, with 14% attaining GTC seizure freedom. Overall, seizure reductions were sustained over time across all age groups and seizure types.

ADRs were reported in 69.2% of patients with DS, most commonly somnolence (37.3%) and decreased appetite (26.5%). Although no new safety signals emerged, the incidence of ADRs increased with age, occurring in 64% of patients younger than 3 years compared with 85% of patients 19 years or older. Notably, growth parameters remained in ± 2 standard deviations throughout follow-up.

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REFERENCES
1. Chancharme L, Vandame D, Kitamura Y, et al. Long-term Effectiveness of Stiripentol in Reducing Seizure Burden and Status Epilepticus in Dravet Syndrome: Results from a 3-Year Japanese Post-Marketing Surveillance. Presented at: AES 2025; December 5-9; Atlanta, Georgia.