GW Pharmaceuticals has unveiled yet more positive data from a late-stage programme testing its cannabinoid Epidiolex in rare epilepsies, pushing its stock up more than 16 percent after the announcement.

A second randomised, double-blind, placebo-controlled Phase III clinical trial of the drug in patients with the severe form of childhood-onset epilepsy Lennox-Gastaut Syndrome has achieved its primary endpoint of reducing seizures with "high statistical significance", the UK group said.

In the study, patients taking Epidiolex 20mg/kg/day achieved a median reduction in monthly drop seizures of 42 percent compared with a reduction of 17 percent in patients taking placebo, while those taking the 10mg/kg/day dose achieved a median cut in monthly drop seizures of 37 percent compared with a reduction of 17 percent in patients taking placebo.

Also, on the safety side, the drug was considered to be well tolerated. Of the 84 percent of 10mg/kg patients who experienced an adverse event, 89 percent of them deemed it to be mild or moderate, with figures for the higher dose group 94 percent and 88 percent respectively. In the placebo arm, 72 percent of patients experienced side effects.

On the back of these results, and of those released earlier this year from late-stage trials of the medicine in LGS and Dravet syndrome, another rare and difficult to treat childhood epilepsy, the firm is planning to submit a new drug application to US regulators in the first half of next year.

"The positive outcome in this second trial of Epidiolex in patients with Lennox-Gastaut syndrome demonstrates the effectiveness of this product in this particularly difficult to treat, childhood-onset epilepsy," noted Orrin Devinsky, MD of New York University Langone Medical Center's Comprehensive Epilepsy Center and principal investigator in the trial.

"The data from the Epidiolex Dravet and LGS studies offers the prospect of an FDA-approved CBD medicine that shows both clinically meaningful seizure reduction and a consistent safety and tolerability profile."

The drug is also being tested for the treatment of seizures associated with the rare genetic disorder Tuberous Sclerosis Complex, of which epilepsy is a key symptom.