The purpose of the study is to test the efficacy, safety and tolerability of brivaracetam monotherapy in study participants 2 to 25 years of age inclusive with childhood absence epilepsy (CAE) or juvenile absence epilepsy (JAE).

Inclusion Criteria:

• Study participant is 2 to 25 years of age inclusive, at the time of signing the informed consent. No study participants from 2 to <4 years of age will be included in Stage 1

• Study participant is diagnosed with either childhood absence epilepsy (CAE) or juvenile absence epilepsy (JAE) as defined by the International League Against Epilepsy (ILAE) criteria

• Study participants 2 to <4 years of age and participants who had onset of absence seizures at an age younger than 4 years must have a negative glucose transporter type 1 deficiency syndrome (GLUT1DS) genetic test

• Study participant is untreated with antiepileptic drugs (AEDs) or pretreated for absence seizures with a maximum of 2 historical AEDs, but without AED treatment for a period of at least 5 half-lives of the AED before randomization into this study. The UCB study physician should be consulted if in doubt

• Study participant has electroencephalogram (EEG) evidence of bilateral synchronous, symmetric generalized paroxysmal spike waves (2.5-6 hertz) with normal background activity and with at least 1 electrographically recorded seizure lasting 3 seconds or more on a 1-hour EEG with hyperventilation (HV) while awake at Visit 1 (V1), or on a historical EEG up to 12 weeks before enrollment

• Study participant has a history of clinically evident absence seizures occurring on at least 3 days per week in the 2 weeks prior to enrollment

• Study participant is without treatment with psychoactive drugs or on a stable dose for at least 2 weeks prior to randomization

• Study participant has normal neurological examination, head size, development and cognition

• Body weight is more than or equal to 9 kg

• Male and female

  a) A sexually active male study participant must agree to use contraception during the treatment period and for at least 2 days, corresponding to the time needed to eliminate study treatment, after the last dose of study treatment and refrain from donating sperm during this period b) A female study participant is eligible to participate if she is not pregnant, not breastfeeding, and at least 1 of the following conditions applies: The study participant is premenarchial OR A woman of childbearing potential (WOCBP) who agrees to follow the contraceptive guidance during the treatment period and for at least 2 days after the last dose of study treatment, corresponding to the time needed to eliminate study treatment

• Study participant provides consent/assent, and the study participant's parent/legal representative/caregiver provides signed informed consent for minor study participants, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol

Exclusion Criteria:

• Study participant has a history of nonfebrile seizures other than absence seizures (eg, generalized tonic-clonic seizures or myoclonic seizures)
• Study participant has a history of absence status epilepticus
• Study participant has a history or presence of paroxysmal nonepileptic seizures
• Study participant has a clinically relevant electrocardiogram (ECG) abnormality in the opinion of the Principal Investigator
• Study participant has hepatic impairment (Child Pugh Score A, B, or C) based on the Investigator's assessment
• Study participant has a history of major psychiatric disease or any clinically significant medical condition that would preclude appropriate study participation
• Study participant has active suicidal ideation prior to study entry as indicated by a positive response ("Yes") to either Question 4 or Question 5 of the Columbia-Suicide Severity Rating Scale (C-SSRS; for study participants 6 years or older) or clinical judgement (for study participants younger than 6 years). The study participant should be referred immediately to a Mental Healthcare Professional
• Study participant has a lifetime history of suicide attempt (including an active attempt, interrupted attempt, or aborted attempt). The study participant should be immediately evaluated by a Mental Healthcare Professional to address safety concerns
• Study participant with known fructose intolerance or hypersensitivity of any of the ingredients in brivaracetam oral solution
• Study participant has end-stage kidney disease requiring dialysis
• Concomitant use of rifampicin/rifampin; prior use must have been stopped at least 2 months before randomization
• Concomitant use of strong CYP2C19 inhibitors like fluconazole, fluoxetine and fluvoxamine, prior use must have been stopped at least 1 week before randomization
• Study participant has participated in another study of an investigational medicinal product (IMP; and/or an investigational device) within the previous 30 days prior to informed consent
• Study participant has clinical or EEG findings not consistent with a diagnosis of childhood absence epilepsy (CAE) or juvenile absence epilepsy (JAE)

Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe, or global development is discontinued, and 18 months after trial completion. Investigators may request access to anonymized individual patient-level data and redacted trial documents which may include: analysis-ready datasets, study protocol, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a prespecified time, typically 12 months, on a password protected portal. This plan may change if the risk of re-identifying trial participants is determined to be too high after the trial is completed; in this case and to protect participants, individual patient-level data would not be made available.

Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe or global development is discontinued, and 18 months after trial completion.

Qualified researchers may request access to anonymized IPD and redacted study documents which may include: raw datasets, analysis-ready datasets, study protocol, blank case report form, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal.