Epidiolex is an oral cannabidiol (CBD) solution. It is approved by the U.S. Food and Drug Administration (FDA) for the treatment of seizures in Dravet syndrome and Lennox-Gastaut syndrome. GW Pharmaceuticals is currently investigating Epidiolex as a potential treatment for neurobehavioral deficits and seizures in Rett syndrome.

How Epidiolex works

The active ingredient of Epidiolex, CBD, is a compound isolated from the cannabis plant. Cannabis’ psychoactive effects are caused by delta (9)-tetrahydrocannabinol (THC); Epidiolex does not cause these effects but is known to have neuroprotective abilities. It is not fully understood how Epidiolex reduces seizures and improves neurobehavioral deficits.

Rett syndrome is caused by mutations in the MECP2 gene, which encodes for a protein crucial to brain development and function. The mutations lead to a loss of function in this protein, causing motor and behavioral abnormalities and seizures. Cannabinoids such as CBD are known to trigger the release of neurotransmitters, or signaling molecules, with which nerve cells communicate. Because neurotransmitters play a crucial role in the function and maintenance of nerve cells, changes in neurotransmitter release likely contribute to CBD’s neuroprotective effects in Rett syndrome.

Epidiolex in clinical trials

A preclinical study investigated the cannabidiol homolog (a compound similar to cannabidiol) cannabidivarin in a mouse model for Rett syndrome. After 14 days of treatment with cannabidivarin, motor function and social behavior had significantly improved in the animals.

A Phase 3 clinical trial (NCT03848832) plans to investigate the efficacy of Epidiolex in reducing symptom severity in Rett syndrome patients. The trial will take place at sites across the U.S. and the U.K.


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