Epidiolex (cannabidiol), an oral medication developed by GW pharmaceuticals, is approved by the U.S. Food and Drug Administration for the treatment of seizures in Lennox-Gastaut syndrome patients, ages 2 and older. Epidiolex is also approved by the European Commission, under the brand name Epidyolex, as an add-on therapy to clobazam.

In addition, Epidiolex is approved for the treatment of Dravet syndrome.

How does Epidiolex work?

Epidiolex is an oral cannabidiol solution derived from the cannabis or marijuana plant. Cannabidiol is a non-psychoactive extract from marijuana, which means that Epidiolex does not have the characteristic “high” effect that is associated with marijuana use.

Cannabis products have been used to treat seizures for centuries but the exact mechanism of action is unclear. A seizure is the result of abnormal brain activity. The endocannabinoid system (ECS) of the brain and spinal cord plays a vital role in modulating several essential neurological functions, including the release of hormones and the activity of nerve cells. Cannabidiol may exert an anti-seizure effect by indirectly regulating ECS activity. It may also modulate the levels of calcium, which is essential for the proper communication between nerve cells.

Epidiolex in clinical trials

Epidiolex has been evaluated for the treatment of seizures associated with Lennox-Gastaut syndrome and Dravet syndrome. The key studies conducted in Lennox-Gastaut syndrome patients are summarized below.

An international Phase 3 study (NCT02224560) compared the safety and efficacy of Epidiolex versus a placebo in patients, ages 2 to 55. A total of 225 patients were enrolled in this study at sites in the U.S., France, Spain, and the U.K. Patients were randomly grouped to receive either 20 mg/kg of Epidiolex, 10 mg/kg of Epidiolex, or a placebo daily for 14 weeks. The median reduction in atonic seizure frequency during the treatment period was 41.9% in patients taking 20 mg/Kg of Epidiolex, 37.2% in those taking 10 mg/kg of Epidiolex, and 17.2% in the placebo group, according to results published in The New England Journal of Medicine. Adverse events were most common in the highest Epidiolex dose group and included sleepiness, diarrhea, and decreased appetite.

A Phase 3 multicenter study (NCT02224690) conducted in the U.S., the Netherlands, and Poland evaluated the efficacy of Epidiolex as an add-on therapy for atonic seizures in patients who did not respond to other treatments alone. A total of 171 patients, ages 2 to 55, were randomly grouped to receive either 20 mg/kg of oral Epidiolex or a placebo daily for 14 weeks. The frequency of atonic seizures was reduced by a median of 43.9% in the Epidiolex group compared to 21.8% in the placebo group in a month, according to results published in the journal The Lancet. Diarrhea, decreased appetite, fever, sleepiness, and vomiting were the most common side effects.

A Phase 3 extension study (NCT02224573), which included participants from previous placebo-controlled studies of Epidiolex, recruited 681 patients with Lennox-Gastaut syndrome or Dravet syndrome. The follow-up duration for the study is five years. The ongoing study is expected to be completed in June 2020.

A new Phase 4 study (NCT04133480) will assess the impact of Epidiolex on the cognitive abilities of children with Lennox-Gastaut syndrome, ages 3 to 10. The 30-week open-label study aims to enroll a total of 116 patients. For the first seven days, participants will receive 5 mg/kg of oral Epidiolex, and the dose will be increased and maintained at 10 mg/kg daily for the rest of the study. The dosage may be increased further to 20 mg/kg daily if deemed necessary by the investigators. The National Institutes of Health Toolbox Cognition Battery will be used to assess cognitive function. The study has not started enrolling participants yet.


Last updated: Nov. 2, 2019


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