Drug Development

GW Pharma details an impressive PhIII case for a cannabis-based drug for severe epilepsy as it preps an NDA

Orrin Devinsky, NYU Langone Medical Center

GW Pharmaceuticals lined up a straight shot at a key approval for Epidiolex today, publishing its impressive Phase III data for a severe form of childhood epilepsy which inspired a blockbuster forecast for the cannabis-based therapy.

GW announced last spring that Epidiolex — a liquid therapy using purified cannabadiol — triggered a mean reduction in convulsive seizures of 39% among treatment-resistant patients with Dravet syndrome, compared to only 13% among the placebo group. A report published in The New England Journal of Medicine adds today that 43% of the drug group had a mean drop of 50% or more — compared to 27% in the placebo group. And 5% stopped having seizures, with none in the placebo arm doing as well.

GW Pharma $GWPH now plans to file for an FDA approval sometime in the coming weeks, with analysts projecting peak sales over a billion dollars. GW has had successful trials for both Dravet syndrome as well as another rare form of epilepsy called Lennox-Gastaut syndrome, with plans to file for approvals on both.

GW’s stock jumped 4.4% on the publication of the data, which helps verify their results.

We also got a much better look at the safety data in the NEJM article. A total of 93% of the patients taking the drug experienced a side effect, though most were mild or moderate. AEs were registered for somnolence, diarrhea, decreased appetite, fatigue, vomiting, pyrexia, lethargy, convulsion and upper respiratory tract infections. Ten patients in the drug arm dropped out of the study, compared to 3 patients on placebo.

Most seriously, 12 patients experienced a spike in liver enzymes — a classic red flag on toxicity — and 4 dropped out of the study. Of the other 9 who stayed, all saw liver enzyme levels return to normal.

Leerink’s Paul Matteis, though, sounded a note of concern about two issues that could trip up GW Pharma. In a note to investors, he wrote:

From our conversations with investors we’ve heard two bear points on Epidiolex ahead of an NDA filing: (1) that clobazam may have been a major contributor to Epidiolex’s efficacy [and that this could ultimately prove to be important to or problematic for FDA]; and (2) that liver enzyme elevations on Epidiolex could in part hinder broad use, possibly via unfavorable labeling language. We don’t really understand the latter concern since valproate – an anti-epileptic with a black box warning for hepatotoxicity and more serious liver enzyme issues than observed in GW’s ph3 program – is broadly used in the refractory epilepsy setting. However, regarding the clobazam drug-drug interaction, seizure reduction sub-group analyses remain of interest. GW has suggested that these analyses could be presented before a potential FDA advisory committee but specific guidance has not been communicated.

“Dravet syndrome is one of the most difficult types of epilepsy to treat and many of the children in this study were experiencing dozens, even hundreds, of seizures per month despite taking multiple concurrent anti-epileptic medications,” said Orrin Devinsky, the lead author from the NYU Langone Medical Center’s Comprehensive Epilepsy Center. “These results suggest that Epidiolex can provide clinically meaningful benefits and I look forward to the prospect of an appropriately standardized and tested pharmaceutical formulation of cannabidiol available as a treatment option for these patients.”

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