GW Pharma surges as epilepsy drug succeeds at phase 3

Shares in UK-based GW Pharma have surged after a phase 3 study of its cannabis-based Epidiolex (cannabidiol) met primary endpoint in Dravet syndrome, a rare kind of childhood epilepsy.

In study results announced today, Epidiolex significantly reduced convulsive seizures assessed over the entire treatment period compared with placebo.

Analysts estimate the drug could generate annual sales of $1.1 billion by 2021, according to consensus forecasts compiled by Thomson Reuters Cortellis.

Shares in GW, which already markets Sativex (nabiximols) for multiple sclerosis spasticity, jumped in value from around £2 to almost £5 in trading on the London Stock Exchange following the announcement.

GW's CEO, Justin Gover said the company is requesting a meeting with the US Food and Drug Administration to discuss a filing.

The phase 3 study randomised 120 patients into two arms, Epidiolex 20mg/kg/day and placebo. Epidiolex or placebo was added to current anti-epileptic drug treatment regimens.

On average, patients were taking approximately three epilepsy drugs, having previously tried and failed an average of more than four others.

The average age of trial participants was 10 years and 30% of patients were less than 6 years of age. The median baseline convulsive seizure frequency per month was 13.

The primary efficacy endpoint was a comparison between Epidiolex and placebo measuring the percentage change in the monthly frequency of convulsive seizures during the 14-week treatment period compared with the 4-week baseline observation period.

In this study, patients taking Epidiolex achieved a median reduction in monthly convulsive seizures of 39% compared with a reduction on placebo of 1%. The highly statistically significant result was confirmed with a series of sensitivity analyses, GW said.

The difference between Epidiolex and placebo emerged during the first month of treatment and was sustained during the entire treatment period.

Results from secondary efficacy endpoints reinforced the overall effectiveness observed with Epidiolex.

GW said Epidiolex was generally well tolerated and the most common adverse events, occurring in greater than 10% of Epidiolex treated patients, were somnolence, diarrhoea, decreased appetite, fatigue, pyrexia, vomiting, lethargy, upper respiratory tract infection and convulsion.

Of those patients on Epidiolex that reported an adverse event, 84% reported it to be mild or moderate. Ten patients on Epidiolex experienced a serious adverse event compared with three patients on placebo. Eight patients on Epidiolex discontinued treatment due to adverse events compared with one patient on placebo.

GW is conducting a second phase 3 trial in Dravet syndrome which is recruiting 150 patients.

Results from another phase 3 trial of Epidiolex in Lennox-Gastaut syndrome, another rare form of epilepsy, are due in Q2 2016. A phase 3 trial in Tuberous Sclerosis Complex, a third paediatric epilepsy indication, is due to begin soon, and clinical development in a fourth indication is due to commence in the second half of 2016.