Experience in the use of clobazam in the treatment of Lennox–Gastaut syndrome

Clobazam is a 1,5-benzodiazepine used successfully worldwide since the 1970s as an anxiolytic and antiepileptic drug. Since its recent Food and Drug Administration (FDA) approval in the United States in 2011 as adjunctive treatment for Lennox–Gastaut syndrome, it has continued to show sustained efficacy and a better safety and tolerability profile compared with other benzodiazepines. The two randomized, controlled studies that led to the US FDA approval, as well as the follow-up multicenter, open-label study of clobazam, showed ≥50% seizure reduction for more than 50% of Lennox–Gastaut syndrome patients, while none of the other FDA-approved treatments for LGS have demonstrated efficacy rates better than 50%. Clobazam appears to have a safe profile and sustained effectiveness over the first 3 years of use in LGS and other epilepsy syndromes with intractable seizures, which makes it a viable long-term treatment option

High Rate of Recurrent De Novo Mutations in Developmental and Epileptic Encephalopathies

Developmental and epileptic encephalopathy (DEE) is a group of conditions characterized by the co-occurrence of epilepsy and intellectual disability (ID), typically with developmental plateauing or regression associated with frequent epileptiform activity. The cause of DEE remains unknown in the majority of cases. We performed whole-genome sequencing (WGS) in 197 individuals with unexplained DEE and pharmaco-resistant seizures and in their unaffected parents. We focused our attention on de novo mutations (DNMs) and identified candidate genes containing such variants. We sought to identify additional subjects with DNMs in these genes by performing targeted sequencing in another series of individuals with DEE and by mining various sequencing datasets. We also performed meta-analyses to document enrichment of DNMs in candidate genes by leveraging our WGS dataset with those of several DEE and ID series. By combining these strategies, we were able to provide a causal link between DEE and the following genes: NTRK2, GABRB2, CLTC, DHDDS, NUS1, RAB11A, GABBR2, and SNAP25. Overall, we established a molecular diagnosis in 63/197 (32%) individuals in our WGS series. The main cause of DEE in these individuals was de novo point mutations (53/63 solved cases), followed by inherited mutations (6/63 solved cases) and de novo CNVs (4/63 solved cases). De novo missense variants explained a larger proportion of individuals in our series than in other series that were primarily ascertained because of ID. Moreover, these DNMs were more frequently recurrent than those identified in ID series. These observations indicate that the genetic landscape of DEE might be different from that of ID without epilepsy