ETX101 is a recombinant adeno-associated viral (AAV) vector containing a GABA regulatory element designed to upregulate SCN1A (encoding the voltage-gated sodium channel NaV1.1) and restore interneuron function in patients with Dravet Syndrome. The gene discussed is SCN1A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.