GW Pharmaceuticals rockets on positive results for Dravet epilepsy tests

Shares in GW Pharmaceuticals rocketed up more than 120% after revealed exciting results of its cannabis-based treatment for children with a rare form of epilepsy.

The company’s first major paediatric epilepsy trial for its Epidiolex drug achieved its primary endpoint with high statistical significance, showing that the treatment significantly reduced convulsive seizures in children with Dravet syndrome compared to placebo.

LSE- and Nasdaq-listed GW said tit was "the most important clinical news in the company’s history".

Dravet syndrome is a rare, severe and difficult to treat form of childhood epilepsy, affecting 1:20,000 to 1:40,000 patients and with considerable unmet as there is no approved treatment in the US market.

"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 standardized and tested pharmaceutical formulation of cannabidiol being made available by prescription in the future."

In the trial of 120 children with an average age of 10 years old, Epidiolex treatment led to a median reduction in convulsive seizures of 39% compared to 13% on placebo. Tolerance of the drug was encouraging, the company said, with 84% of those reporting adverse events saying they mild or moderate, with 10 patients experiencing serious adverse effects compared with three patients on placebo.

"These are clinically meaningful and important reductions in seizures in otherwise treatment-resistant children," GW said.

GW also hopes to publish results of a trial into Lennox-Gastaut syndrome, another rare form of epilepsy, in the second quarter of the year.

In a recent note, analysts at Numis suggested the trial may be underpowered.

"We have sought independent statistical advice that suggests 224 patients per group, rather than the circa 60, are required for appropriate powering based on the raw data available and our analysis of the potential placebo response. GW may need to pool all four Phase 3 studies (two Dravet amd two LennoxGastaut trials reporting in 2016) to achieve adequate statistical powering, and even then a high placebo response could confound the analysis."

Shares in GWP soared 266p to 483.18p, a rise of 123.18%, not long after the statement was published at 1100 GMT.