Inclusion Criteria

• Male or female
• Aged between 2 and 55 years inclusive
• Must have a documented history of Lennox-Gastaut syndrome
  • Includes written documentation of having met electroencephalogram (EEG) diagnostic criteria during the patient's history
  • Evidence of at least one type of generalized seizure, including drop seizures (atonic, tonic, tonic-clonic or myoclonic) for at least six months
• Have a history of slow (<2.5 Hz) spike-and-wave pattern in an EEG prior to the enrollment into the baseline period
• Should be refractory, that is having documented failures on more than one antiepileptic drug
• Must be taking one or more antiepileptic drug at a dose which has been stable for at least four weeks prior to screening
• All medications or interventions for epilepsy (including ketogenic diet and vagus nerve stimulation [VNS]) must have been stable for four weeks prior to screening and patient is willing to maintain a stable regimen throughout the study
  • The ketogenic diet and VNS treatments are not accounted as an antiepileptic drug

Exclusion Criteria

• Etiology of subject's seizures is a progressive neurologic disease
  • Subjects with tuberous sclerosis will not be excluded from study participation, unless there is a progressive tumor
• Has had an anoxic episode requiring resuscitation within six months of screening
• Has clinically significant unstable medical conditions other than epilepsy
• Has had clinically relevant symptoms or a clinically significant illness in the four weeks prior to screening or randomization, other than epilepsy
• Is currently using or has in the past used recreational or medicinal cannabis, or synthetic cannabinoid based medications (including Sativex®) within the three months prior to study entry and is unwilling to abstain for the duration of the study
• Has any known or suspected hypersensitivity to cannabinoids or any of the excipients of the Investigational Medicinal Product (IMP), such as sesame oil
• Has been part of a clinical trial involving another IMP in the previous six months
• Has significantly impaired hepatic function at screening (Visit 1) or randomization (Visit 2)
  • Alanine aminotransferase [ALT] >5 x upper limit of normal [ULN]
  • Or total bilirubin [TBL] >2 x ULN
  • Or the ALT or Aspartate aminotransferase (AST) >3 x ULN and TBL >2 x ULN or international normalized ratio >1.5
  • This criterion can only be confirmed once the laboratory results are available
  • Subjects randomized into the study who are later found not to meet this criterion should be withdrawn from the study
• Any history of suicidal behavior or any suicidal ideation of type four or five on the Columbia Suicide Severity Rating Scale in the last month or at screening
• Is taking more than four concurrent antiepileptic drugs
• Has taken corticotropins in the six months prior to screening
• Is currently taking long-term systemic steroids (excluding inhaled medication for asthma treatment) or any other daily medication known to exacerbate epilepsy
  • An exception will be made of prophylactic medication, for example, for idiopathic nephrotic syndrome or asthma
• Is taking felbamate, and has been taking it for less than one year prior to screening