Preliminary sales figures for the first cannabis-based medicine in the United States are in and they're telling a bullish story, according to GW Pharmaceuticals CEO Justin Gover.

Epidiolex, which contains cannabidiol to treat severe forms of epilepsy, brought in $104 million in net sales in the fourth quarter and a total of $296 million in 2019 across the globe, the British pharmaceutical company preannounced for its quarterly and full-year performances.

"It's an incredible launch year for any medication [that] I think proves that this kind of medicine is really making a difference to patients," Gover told CNBC's Jim Cramer in a "Mad Money" interview. "It shows real value to the health-care system, and it sets us up, I think, in a very nice way for what should be another great year for us in 2020."

The U.S. Food and Drug Administration approved Epidiolex in 2018, and the oral solution became available later that year for patients ages two and older with Lennox-Gastaut syndrome and Dravet syndrome, two rare and severe forms of epilepsy. In 2015, about 3.4 million people were diagnosed with the central nervous system disorder, according to the Centers for Disease Control and Prevention.

"It's a new mechanism to treat epilepsy. We're obviously treating very high-need patients, often children. They're having many seizures a day," Gover said. "So the ability to provide a real advance in this therapeutic area, together with the fact that this is the first ever cannabis product approved by the FDA, has together created I think an exceptional environment for us to commercialize this product."

Cannabidiol, commonly known as CBD, is a component from the marijuana plant that doesn't cause intoxication when consumed. The high associated with cannabis comes from tetrahydrocannabinol, or THC, which remains illegal federally but has been legalized for medicinal or recreational purposes in most states.

GW Pharma last year received approval from the European Union to market the same drug as Epidiolex in 28 countries on the continent. The company said it would roll out the product in France, Germany and the United Kingdom in the fourth quarter of 2019, followed by Spain and Italy this year.

GW Pharma is expected to report fourth-quarter and full-year 2019 earnings in late February. Epidiolex sales accounted for almost all of the company's revenue.

Wall Street is estimating $103.1 million in revenue for the fourth quarter and $305.2 million in revenue for the full year, according to FactSet. That would represent a huge boost from the $12.7 million GW Pharmaceuticals brought in the year prior. Analysts are anticipating the company will break even on profitability.

Shares of GW Pharma rose nearly 2% to just under $120 per share in Thursday's session.