PRAX-628 for Adult Focal Seizures

Inclusion Criteria: 1. A diagnosis of focal onset epilepsy according to the International League Against Epilepsy (ILAE) Classification of Epilepsy. 2. Past evidence by computed tomography (CT) or magnetic resonance imaging (MRI) that has ruled out a progressive cause of epilepsy in the judgement of the investigator and/or in consultation with the medical monitor. Exclusion Criteria: 1. Subject has had any of the of the following within the 12-month period preceding trial entry: History of pseudo or psychogenic seizures, cluster seizures where the individual seizures cannot be counted, an episode of convulsive status epilepticus requiring hospitalization and intubation, or subject only has focal seizures with awareness that do not have motor activity. 2. Planned epilepsy surgery during the course of the clinical trial. 3. History of neurosurgery for seizures \<1 year prior to enrollment, or radiosurgery \<2 years prior to enrollment or vagus nerve stimulation (VNS) implantation. 4. History of schizophrenia, obsessive-compulsive disorder, or other serious mental health disorders. 5. History of malignancy, myeloproliferative or lymphoproliferative disorders within the past 5 years are excluded. 6. History of cardiac disease(s)/cardiac conduction disorders/or cardiac structural abnormality(ies). 7. Has a positive test result or a known history of a positive test result for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), or anti-hepatitis C virus (HCV) antibody at Screening. 8. Is pregnant or is breastfeeding at the time of Screening or has a positive serum pregnancy test at Screening or is planning to become pregnant during the clinical trial or within 14 days of the last study drug dose. 9. Has received any other experimental or investigational drug, device or other therapy within 30 days or 5 half-lives (whichever is longer) prior to Screening, or any prior use of gene therapy.