Multiple phase 1/2 studies are currently examining ETX101, an AAV serotype 9 (AAV9) gene therapy designed to express voltage-gated sodium channels (NaV1.1) in GABAergic inhibitory interneurons [64] in children with SCN1A-positive Dravet syndrome [148,149,150]. The gene discussed is SCN1A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.