What happened

Shares of Zogenix, Inc(NASDAQ:ZGNX) skyrocketed 196% higher in September after the company reported data from a study that suggested low-dose fenfluramine lowers the rate of seizures in Dravet syndrome patients by more than GW Pharmaceuticals' (NASDAQ:GWPH) marijuana-based drug Epidiolex.

So what

Zogenix's ZX008 may soon offer new hope to patients living with a rare form of epilepsy called Dravet syndrome. 

A rocket soaring into space.


Dravet syndrome is an uncommon and debilitating form of childhood-onset epilepsy that's inadequately treated with existing anti-epileptic medications.

Because there's a big unmet need for new treatment options in the indication, GW Pharmaceuticals' shares rallied to all-time highs last year following news that its marijuana-based drug, Epidiolex, can lower monthly seizures by about 40%. Epidiolex is a purified formulation of cannabidiol (CBD), a common chemical found in marijuana.

Epidiolex's efficacy reinforces the long-held belief that marijuana strains that are high in cannabidiol (CBD) can help epilepsy patients, but data from Zogenix's low-dose fenfluramine (ZX008) trial suggests it may control seizures in tough-to-treat epilepsy even better than marijuana.

Patients taking 0.8 mg of ZX008 saw the number of their monthly seizures decline by an average 64% and median 72%. For perspective, people taking a placebo only saw a median 17.4% decline in monthly seizures. Only 2.5% of patients who took the placebo achieved a 75% or greater reduction in monthly seizures, while 45% of patients in the Zogenix study achieved that level of benefit. 

Now what

GW Pharmaceuticals has a headstart because its trials have already wrapped up and it plans to file for an FDA approval soon. That puts Epidiolex's potential launch sometime next year. 

Zogenix is still waiting for confirmatory data from a second phase 3 trial, and that data isn't expected until next year. That suggests that ZX008 might not hit the market until sometime in 2019, depending on the exact timing of its filing.

Initially, both drugs will target a limited patient population. However, each has the potential to see their use expand to more patients because, frankly, current antiepileptics inadequately control seizures for many patients. Since the market for epilepsy treatment is a big one, peak sales for these drugs could be in the nine figures.

Which drug will get prescribed the most? It depends on ZX008's second phase 3 trial results and doctors' views of the safety profiles of the two drugs. Stay tuned.

Todd Campbell has no position in any of the stocks mentioned. His clients may have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.