Shares in GW Pharmaceuticals surged nearly 140% as it emerged that experimental cannabinoid Epidiolex hit targets in the first major paediatric trial investigating its potential in a rare and very difficult to treat form of childhood epilepsy called Dravet syndrome.

Data from the 14-week, 120-patient, Phase III study showed that Epidiolex achieved the primary endpoint of a significant reduction in convulsive seizures over the entire treatment period compared with placebo.

On average, patients were taking about three anti-epileptic drugs (AEDs), having previously tried and failed an average of more than four other AEDs. The average age of trial participants was 10 years and 30 percent of patients were less than six years of age.

Those taking Epidiolex achieved a median reduction in monthly convulsive seizures of 39 percent compared with a reduction on placebo of 13 percent, which was highly statistically significant. Results from secondary efficacy endpoints reinforce the overall effectiveness observed with the drug, which was also found to be well-tolerated in the study, the firm noted.

Epidiolex has been awarded both Orphan Drug Designation and Fast Track Designation by the US Food and Drug Administration as a treatment for Dravet syndrome, for which there are currently no approved therapies in the country.

“The results of this Epidiolex pivotal trial are important and exciting as they represent the first placebo-controlled evidence to support the safety and efficacy of pharmaceutical cannabidiol in children with Dravet syndrome, one of the most severe and difficult-to-treat types of epilepsy,” said Orrin Devinsky, of New York University Langone Medical Center’s Comprehensive Epilepsy Center. 

“These data demonstrate that Epidiolex delivers clinically important reductions in seizure frequency together with an acceptable safety and tolerability profile, providing the epilepsy community with the prospect of an appropriately standardised and tested pharmaceutical formulation of cannabidiol being made available by prescription in the future.”

In addition to this first Phase III trial, GW is also conducting a second in Dravet syndrome which is recruiting 150 patients, while studies involving patients with Lennox-Gastaut syndrome (LGS), another difficult-to-treat and rare form of childhood epilepsy, are also ongoing.