Assessment of Adjunctive Cannabidiol Oral Solution (GWP42003-P) in Children With Tuberous Sclerosis Complex (TSC), Dravet Syndrome (DS), or Lennox-Gastaut Syndrome (LGS) Who Experience Inadequately-controlled Seizures

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/baseline.

Has clinically significant abnormalities in the electrocardiogram (ECG) measured at screening/baseline.

Has any concurrent cardiovascular conditions, that 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 study intervention such as sesame seed oil.

Has significantly impaired hepatic function prior to Visit 3, 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).

* Serum ALT or AST \> 5 × ULN.

* Serum ALT or AST \> 3 × ULN with the presence of fatigue, nausea, vomiting, right upper quadrant pain or tenderness, fever, rash, and/or eosinophilia (\> 5%).

* Elevated ALT or AST should be discussed with the medical monitor prior to Visit 3; the medical monitor may allow for a confirmatory re-draw prior to Visit 3.

Has received another study intervention within 4 weeks prior to Visit 1 or plans to take another study intervention during the study.

Has any other clinically significant disease or disorder which, in the opinion of the investigator, may either put the participant, other participants, or site staff at risk because of participation in the study, may influence the result of the study, or may affect the participant's ability to take part in the study.

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 study.

Has previously been enrolled into this study.

Has plans to travel outside their country of residence during the study, unless the participant has confirmation that the study intervention is permitted in the destination country.

What this study is about