Safety, Pharmacokinetics, and Exploratory Efficacy Assessment of Adjunctive Cannabidiol Oral Solution (GWP42003-P) Compared With Standard of Care Antiseizure Medication, in Participants Age 1 Month to <12 Months of Age With Tuberous Sclerosis Complex Who Experience Inadequately-controlled Seizures

Inclusion Criteria:

• Must be 1 month to < 12 months of age at the time of initial informed consent
• Parent(s)/legal representative is/are willing and able to give informed consent for participation in the trial.
• Parent(s)/legal representative is/are willing and able (in the investigator's opinion) to comply with all trial requirements (including accurate electronic participant-reported outcome [ePRO] diary completion).
• Must have a clinical diagnosis of tuberous sclerosis complex (TSC) according to the investigator and as defined by 2012 International TSC Consensus Conference and International League Against Epilepsy (ILAE) Classification.
• Multichannel (minimum 8-channel) 8- to 24-hour video electroencephalogram (VEEG), to be read prior to Part A Visit 3 by the investigator and an independent reviewer, for confirmation of diagnosis of inadequately-controlled seizures (may be collected from the participant's medical record if suitable).
• Has seizures which are not adequately controlled through their current antiseizure medications (ASMs), defined as ≥ 1 seizure reported on the paper and ePRO seizure diary during the baseline period

Part B Only:

• Has completed Visit 12 of Part A, if randomized to GWP42003-P and SOC ASM or completed at least 26 days of Part A if randomized to SOC ASM.
• Was compliant with all requirements of Part A (e.g., dosing, paper and ePRO diary, participant visits/procedures), in the opinion of the investigator and sponsor.
• Investigator considers continued treatment in a 1-year extension trial represents a favorable risk-benefit assessment for the participant.

Exclusion Criteria:

Part A Only:

• Has tumor growth which, in the opinion of the investigator, could affect participant safety.
• Has clinically significant abnormal laboratory values, in the investigator's opinion, at screening or baseline.
• Has clinically significant abnormalities in the electrocardiogram (ECG) measured at screening or randomization. Including, QT interval corrected for heart rate with Bazett's formula (QTcB), of > 460 milliseconds (msec) on ECG.
• Has any concurrent cardiovascular conditions, which will, in the investigator's opinion, interfere with the ability to assess their ECGs.
• Has any known or suspected hypersensitivity to cannabinoids or any of the excipients of the investigational medicinal product (IMP) such as sesame seed oil.

• Has significantly impaired hepatic function prior to randomization, defined as:

  • Serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 3 × upper limit of normal (ULN) and (total bilirubin [TBL] > 2 × ULN or international normalized ratio [INR] > 1.5).
  • Elevated ALT or AST should be discussed with the medical monitor prior to randomization; the medical monitor may allow for a confirmatory re-draw prior to randomization.
• Has any other clinically significant disease or disorder which, in the opinion of the investigator, may either put the participant at risk because of participation in the trial, may influence the result of the trial, or may affect the participant's ability to take part in the trial.
• Any clinically significant abnormalities identified following a physical examination of the participant that, in the opinion of the investigator, would jeopardize the safety of the participant if they took part in the trial.
• Has previously been randomized into this trial.
• Has plans to travel outside their country of residence during the trial, unless the participant has confirmation that the IMP is permitted in the destination country.

Part B Only:

• Has tumor growth which, in the opinion of the investigator, could affect the primary endpoint.
• Has clinically significant abnormalities in the ECG in Part A. Including, QTcB of > 460 msec on ECG.
• Has any concurrent cardiovascular conditions, which will, in the investigator's opinion, interfere with the ability to assess their ECGs.
• Has any known or suspected hypersensitivity to cannabinoids or any of the excipients of the IMP such as sesame seed oil.

• Has significantly impaired hepatic function prior to Part B, defined as:

  • Serum ALT or AST > 3 × ULN and (TBL > 2 x ULN or INR > 1.5).
  • Elevated ALT or AST should be discussed with the medical monitor prior to rollover in Part B; the medical monitor may allow for a confirmatory redraw prior to rollover.
• Has any other clinically significant disease or disorder which, in the opinion of the investigator, may either put the participant at risk because of participation in the trial, may influence the result of the trial, or may affect the participant's ability to take part in the trial.
• Any clinically significant abnormalities identified following a physical examination of the participant that, in the opinion of the investigator, would jeopardize the safety of the participant if they took part in the trial.
• Has previously been enrolled in Part B of this trial.
• Has plans to travel outside their country of residence during the trial, unless the participant has confirmation that the IMP is permitted in the destination country.