GW Pharmaceuticals' stock climbs on positive preliminary Epidiolex data in treatment-resistant epilepsy

Shares in GW Pharmaceuticals gained as much as 15 percent Tuesday after announcing that physician reports regarding data for its experimental cannabidiol drug candidate Epidiolex generated under an expanded access programme provide "promising signals of efficacy in children with treatment-resistant epilepsy, including patients with Dravet syndrome." CEO Justin Gover said the efficacy data, "together with the side-effect profile observed to date, support GW Pharma's decision to advance Epidiolex into a formal development programme," adding he expects the therapy to be ready for submission to US and European regulators in 2016.

Specifically, GW Pharma released uncontrolled data on 27 children and young adults who had completed at least 12 weeks of treatment with Epidiolex, with efficacy assessed according to the FDA's recommended endpoint of percent change in average four-week seizure frequency throughout the treatment period, relative to seizure frequency during a four-week baseline period. The company noted that the largest single type of epilepsy in the cohort was Dravet syndrome,while remaining patients comprised a range of treatment-resistant epilepsies with convulsive or non-convulsive seizures. Further, Epidiolex was added to current anti-epileptic drugs in all cases, with patients on average taking 2.7 of such therapies.

The drugmaker reported that, among all patients, the mean and median overall reductions in seizure frequency relative to baseline after 12 weeks of treatment were 44 percent and 42 percent, respectively, while 48 percent of patients experienced at least a 50-percent reduction in seizure frequency. The company added that 15 percent of patients were seizure-free at the end of treatment. In addition, in a subset of nine patients with Dravet syndrome, the mean and median reductions in seizure frequency were 52 percent and 63 percent, respectively, while the seizure frequency was reduced by at least half in 56 percent of patients. Further, 33 percent of these patients were free of seizures at the end of the treatment period.

GW Pharma said 80 percent of reported adverse events were classified as either mild or moderate, and there were no withdrawals from treatment due to negative side effects of the drug. However, the company noted that serious adverse events were reported in seven patients, including one death from sudden unexpected death in epilepsy. "None of these serious adverse events, including the one reported death, were deemed related to Epidiolex by the independent investigators," the drugmaker stated. Meanwhile, GW Pharma also said five additional patients were treated with Epidiolex under an emergency access programme and that three of these "reported perceived benefits after treatment with [the drug] and all five patients remain on treatment."

Gover commented that Epidiolex "has become a central part of [GW Pharma's] valuation," in part due to there being "so much interest among physicians and patients" and because the company owns all worldwide commercial rights to the therapy. Epidiolex received fast-track status from the FDA earlier this month for the treatment of Dravet syndrome, following an orphan drug designation granted for the same indication in November. The company said it plans to start a Phase II/III study testing the therapy in Dravet syndrome in the second half of 2014, as well as an additional late-stage trial for the same indication in the first quarter of next year.

GW Pharma said it also plans to conduct a clinical development programme for Epidiolex as a treatment for Lennox-Gastaut syndrome (LGS) following the receipt of orphan drug status for this indication in February. The drugmaker indicated that it expects to initiate two Phase III trials in LGS next year.

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