Developmental and Epileptic Encephalopathy (DEE) are a group of epilepsies referring to drug-resistant seizures and encephalopathy (significant developmental delays or the loss of developmental skills). Principal Investigator, Scott Harper, of Nationwide Children’s Hospital’s Center for Gene Therapy created a RNAi therapy that decreases the expression of pathogenic variants in the KCNQ3 gene that causes DEE. The therapy uses AAV9 vectors to deliver newly designed microRNA sequences to target the KCNQ3 gene.