Inclusion Criteria:

• Male or female between 6 months through 36 months of age at the time of informed consent as clinical diagnosis of IS, confirmed by video-electroencephalogram (EEG) analysis, and hypsarrhythmia on EEG at screening according to the Burden of Amplitudes and Epileptiform Discharges (BASED) scale score.
• As assessed by the investigator has no or partial response to at least 2 out of the 3 therapies of adrenocorticotrophic hormone (ACTH), vigabatrin, and glucocorticoids (i.e. prednisolone), or has no or partial response to at least 1 out of the 3 therapies of ACTH, vigabatrin, and glucocorticoids and is contraindicated to and/or refused by the patient’s legal representative(s) for treatment with one or both other 2 therapies.
• Patient has general good health (defined as the absence of any clinically relevant abnormalities as determined by the investigator) based on physical and neurological examinations, medical history, normal renal function and electrocardiogram (ECG), and clinical laboratory values completed during the Screening Period visit (Visit 1).

Exclusion Criteria:

• Patient considered by the investigator, for any reason (including, but not limited to, the risks described as precautions and warnings in the current version of the investigator’s brochure for investigational product) to be an unsuitable candidate to receive the investigational product.
• Patient has known or suspected allergy to the investigational product or apple juice.
• Patient has clinically significant renal impairment, defined as creatinine > mg/dL or blood urea nitrogen > 2 × upper limit of normal (ULN); clinically significant liver dysfunction, defined as total bilirubin ≥ 2 × ULN, or aspartate aminotransferase or alanine aminotransferase ≥ 3 × ULN; has clinically significant abnormal laboratory values; the investigator may deem the patient eligible if he/she judges the laboratory values to be not clinically significant.
• Patient has an ongoing or known history of human immunodeficiency virus infection, or chronic hepatitis B or C.
• Patient has a clinically significant abnormality on ECG that, in the opinion of the investigator, increases the safety risks of participating in the study.
• Patient has a neurodegenerative disorder as the underlying cause of IS.
• Patient has a known history of aspiration pneumonia within the past year.
• Patient has previously participated in another clinical study of the investigational product or received any investigational drug or device or investigational therapy within 30 days of study entry.
• Patient has received therapy with felbamate, cannabinoids, ketogenic diet or vagus nerve stimulation within 14 days of screening.
• Patient has received therapy with a medication known to be a CYP3A4 substrate and whose PK has been shown to be impacted in the presence of a CYP3A4 inhibitor within 14 days impacted in the presence of a CYP3A4 inhibitor within 14 days of screening.
• Patient has not remained at stables doses of all drugs used for treating epileptic seizures for at least 14 days prior to screening (except for rescue medications used for acute treatment of breakthrough seizures which are not known to be CYP3A4 substrates and whose PK has not been shown to be impacted in the presence of a CYP3A4 inhibitorist of CYP3A4 substrates]).
• Patient has a lethal or potentially lethal condition other than infantile spasms, with a significant risk of death before 18 months of age such as non-ketotic hyperglycinemia.
• Patient has an underlying metabolic disease associated with glucose intolerance (e.g., glucose transporter deficiencies).
• Patient has a body weight below 5 kg.