Allele-agnostic KCNH1 suppression rescues gain-of-function developmental epileptic encephalopathy

Gain-of-function variants in KCNH1, which encodes the voltage-gated potassium channel Kv10.1, cause developmental and epileptic encephalopathies (DEEs) characterized by seizures, developmental delay and intellectual disability. While pathogenic variants enhance channel activity, loss of KCNH1 is tolerated in humans and mice, suggesting that allele-agnostic gene suppression may represent a viable therapeutic strategy. Here, we developed a gapmer antisense oligonucleotide (ASO) targeting KCNH1 and evaluated its efficacy in human induced pluripotent stem cell (iPSC)-derived neurons and a knock-in mouse model of KCNH1-related disorder. Neurons carrying the pathogenic KCNH1 variants I494V or G375R exhibited a shared phenotype characterized by hyperpolarized resting membrane potential and abnormalities in neuronal network activity despite largely preserved intrinsic firing properties. ASOs efficiently reduced KCNH1 expression without disrupting network activity in control neurons. In contrast, ASO treatment normalized network dysfunction across both mutant genotypes, demonstrating that distinct KCNH1 gain-of-function variants converge on a reversible disease state. To assess the efficacy of ASOs in vivo, we generated a new Kcnh1-R357Q knock-in mouse model that exhibited profound seizures and early mortality. A single ASO treatment reduced seizure burden significantly and restored survival to near-normal levels. Together, these findings establish KCNH1 suppression as a precision therapeutic strategy for KCNH1-related DEEs and provide a framework for treating gain-of-function epilepsies in which partial gene reduction is clinically tolerated.