Shares of GW Pharmaceuticals (GWPH) more than doubled Monday after the cannabis-based drugmaker said it had successfully treated a rare form of epilepsy.

The biopharmaceutical, which focuses on the medical use of chemical cannabinoids found in marijuana, announced its Epidiolex treatment had significantly reduced seizures in patients with Dravet syndrome by 39%. In comparison, placebo patients saw a 13% reduction in seizures during the Phase 3 study—the drug’s final clinical trial.

Dravet syndrome, usually caused by a gene mutation, most often presents itself in an infant’s first year of life and is commonly triggered by high temperatures and fevers. According to the Dravet Foundation, the disorder currently has no standard treatment, with most patients trying a host of different drugs to prevent its onset.

Over a period of 14 weeks, GW conducted the trials with 120 participants who were already taking an average of three anti-epileptic drugs to treat Dravet syndrome, and had tried and failed to see effects from four or more other anti-epileptic drugs. The participants were 10 years old on average.

Due to the positive results, the U.K.-based pharmaceutical company said it planned to meet with the U.S. Food and Drug Administration to discuss its regulatory submission.

“We are excited about the potential for Epidiolex to become the first FDA approved treatment option specifically for Dravet syndrome patients and their families,” Justin Gover, GW’s CEO, said in a statement.

GW, which posted consensus-beating first-quarter revenue of $5.4 million on a $1.20 loss per share, is also plans to test Epidiolex in other other epilepsy-related drug trials: Phase 3 trials of Lennox-Gastaut Syndrome and Tuberous Sclerosis Complex.

The stock is still a way off from its July 15 high of $131.25.

Fellow cannabis-based drugmakers Insys Therapeutics (INSY) and Zynerba Pharmaceuticals (ZYNE) also surged Monday. Shares of Insys rose 15% while Zynerba soared 70%.