An Open-label Extension Trial to Investigate Possible Drug-drug Interactions Between Stiripentol or Valproate and Cannabidiol in Patients With Epilepsy

A Phase 2, Double-blind, Randomized, Placebo-controlled Pharmacokinetic Trial in 2 Parallel Groups to Investigate Possible Drug-drug Interactions Between Stiripentol or Valproate and GWP42003-P in Patients With Epilepsy

This trial consists of 2 parts: a double-blinded phase and an open-label extension phase. The open-label extension phase only will be described in this record. All participants will receive the same dose of GWP42003-P. However, investigators may subsequently decrease or increase the participant's dose until the optimal dose is found.

Note: Participants who enroll in France or Sweden must be aged 18-55 years.

Key Inclusion Criteria:

• Participant must have a documented magnetic resonance imaging/computerized tomography of the brain that ruled out a progressive neurologic condition.

Key Exclusion Criteria:

• Participant has clinically significant unstable medical conditions other than epilepsy.
• Participant has a history of symptoms related to a drop in blood pressure due to postural changes (e.g., dizziness, light-headedness, blurred vision, palpitations, weakness, syncope).
• Participant has any history of suicidal behavior or any suicidal ideation of type 4 or 5 on the C-SSRS in the last month.
• Participant is currently using felbamate and has been taking it for less than 12 months prior to screening visit of the blinded phase of the trial.
• Participant is currently using or has in the past used recreational or medicinal cannabis, or synthetic cannabinoid-based medications (including Sativex®) within the 3 months prior to trial entry.
• Participant has any known or suspected history of any drug abuse or addiction.
• Participant is unwilling to abstain from recreational or medicinal cannabis, or synthetic cannabinoid-based medications (including Sativex) for the duration for the trial.
• Participant has any known or suspected hypersensitivity to cannabinoids or any of the excipients of the Investigational Medicinal Product (IMP), e.g., sesame oil.