What happened

Shares of GW Pharmaceuticals plc (NASDAQ:GWPH), a company developing an epilepsy drug derived from its cannabinoid product platform, tacked on another 6.4% in October according to data from S&P Global Market Intelligence. Investors were pleased to see the company complete a rolling submission of Epidiolex's new drug application, setting the stage for a potential blockbuster drug launch.

So what 

GW Pharmaceuticals is developing Epidiolex, a proprietary cannabinoid, as a treatment for two rare forms of epilepsy. Data from clinical trials supporting the recently completed application suggests it could be a major improvement over available treatments that are often ineffective and poorly tolerated.

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Although Lennox-Gestaut and Dravet syndrome are relatively small indications, an approval would give the company a toehold in the enormous market for epilepsy patients underserved by standard therapies. Differences in opinion about the size of Epidiolex's potential patient population are the reason peak annual sales estimates for the drug range from $280 million to $3 billion.

Now what

The FDA has promised an expedited review that should complete in six months or less, once the review begins. The agency can take up to two months to let a company know it has started a review, which means an approval decision could be ready next July, or sooner. 

Unfortunately, Epidiolex's launch date is anybody's guess. Because the drug is derived from cannabis, there could be an unusually long gap between an FDA approval and Drug Enforcement Agency scheduling. That could be an even bigger problem than it seems. Zogenix (NASDAQ:ZGNX) recently shocked the market with surprising fenfluramine results. The decades-old drug may have a tarnished reputation as an appetite suppressant, but it did a fine job reducing seizure frequency among a group of Dravet syndrome patients.

Zogenix' epilepsy candidate might be miles behind Epidiolex on a standard development timeline but could lose any first-to-market advantage to fenfluramine which is highly unlikely to require DEA scheduling before beginning a commercial launch.

Cory Renauer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.