Inclusion Criteria:

• Participant must be at least 34 weeks of gestational age (GA). In addition, term neonates up to 28 days of postnatal age (PNA) and preterm neonates up to 40 weeks of PMA and 28 days of PNA can be enrolled, at the time of signing the informed consent.
• Participants who have confirmation on video-EEG of ≥ 2 minutes of cumulative ENS or ≥ 3 identifiable ENS prior to entering the Treatment Period (ENS is defined as a seizure lasting for at least 10 seconds on video-EEG), despite receiving previous AED treatment for the treatment of electroencephalographic seizures. The occurrence of ENS during an up to 1-hour period must be confirmed by the local video-EEG reader prior to randomized study drug administration. Video-EEG recording can be shortened per clinical need (e.g., if status epilepticus is detected). If possible, an attempt should be made to record at least 30 minutes of Baseline video-EEG.
• Participants must have received either PB, LEV, or MDZ (in any combination) before entering the study.
• Participants with or without concomitant hypothermia treatment.
• Participant weighs at least 2.3kg at the time of enrollment.
• An Independent Ethics Committee (IEC)-approved written ICF is signed and dated by the participant’s parent(s) or legal representative(s).

Exclusion Criteria:

• Participant with seizures responding to correction of metabolic disturbances (hypoglycemia, hypomagnesemia, or hypocalcemia) or with seizures for which a targeted, known treatment is available.
• Participant has seizures related to prenatal maternal drug use or drug withdrawal.
• Participant has known severe disturbance of hemostasis, as assessed by the investigator.
• Participant has a poor prognosis for survival, as judged by the investigator.
• Participant has a medical condition that could be expected, in the opinion of the investigator, to interfere with study medication absorption, distribution, metabolism, or excretion .
• Participant has a clinically relevant ECG abnormality, in the opinion of the investigator (eg, second or third degree heart block at rest or a corrected QT interval [QTc] ≥ 450ms).
• Participant has a hemodynamically significant congenital heart disease.
• Participant has any clinically relevant cardiac arrhythmia.
• Participant has creatinine clearance < 30mL/minute.
• Participant receiving treatment with PHT, LDC, or other sodium channel blockers at any time.
• Participant requires extracorporeal membrane oxygenation.
• Participant requires or is expected to require phototherapy or exchange transfusion due to elevated bilirubin.
• Participant has 2 x upper limit of normal (ULN) of any of the following: aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), with the following exception:
  • For participants with perinatal asphyxia, elevation of AST, ALT, or ALP 2mg/dL.