S230815

S230815 is an antisense oligonucleotide (ASO) being developed by Servier and Symphogen for the treatment of developmental and epileptic encephalopathies (DEE), particularly those associated with gain-of-function mutations in the KCNT1 gene. KCNT1 encodes the sodium-activated potassium channel protein KNa1.1; pathogenic variants lead to severe, pharmacoresistant seizures and intellectual disability, such as in epilepsy of infancy with migrating focal seizures (EIMFS). S230815 is designed to selectively reduce or modulate the expression of KCNT1 mRNA, thereby decreasing the density of the overactive potassium channels on the neuronal surface. Preclinical data in mouse models have demonstrated that this ASO-mediated reduction in KCNT1 expression can significantly decrease seizure frequency, improve behavioral outcomes, and extend survival. As of early 2026, the drug is in Phase 1/2 clinical development.