A Clinical Trial of PRAX-562 in Subjects With Developmental and Epileptic Encephalopathies (DEE) (EMBOLD)

Inclusion Criteria: Has a documented rare missense variant in SCN2A with onset of seizures occurring in the first three months of life or has a documented de novo (not observed in either parent) missense variant in SCN8A with onset of seizures occurring in the first six months of life. Has a seizure frequency as follows: At least 8 countable motor seizures (as defined in the note below) in the 4 weeks immediately prior to Screening as reported by the parent/legal guardian or in the opinion of the investigator AND At least 8 countable motor seizures (as defined in the note below) during the 28 day Baseline Observation Period (during which seizure frequency is recorded in a daily seizure diary). Additional inclusion criteria apply and will be assessed by the study team. Exclusion Criteria: Has any clinically significant or known pathogenic or likely pathogenic genetic variant other than in SCN2A and SCN8A or a genetic variant that may explain or contribute to the participant's epilepsy and/or developmental disorder. Has a documented, functionally characterized loss-of-function (LoF) missense variant or a presumed LoF variant (nonsense or frameshift variant) based on genetic testing and/or clinical evidence that prior exposure to a sodium channel blocker (SCB) medication worsened seizures. Has 2 or more episodes of convulsive status epilepticus requiring hospitalization and intubation in the 6 months prior to Screening. Additional exclusion criteria apply and will be assessed by the study team.