Jim Cramer strongly endorsed an analyst's bullish call on GW Pharma (GWPH) in his "Stop Trading" segment on CNBC's " Squawk on the Street " today.

The UK-based company is working on prescription medicines based on cannabis to treat a number of medical conditions.

Its stock soared as much as 43 percent to $65.97 after Morgan Stanley started coverage of the stock with an "overweight" rating and a price target of $103.

Cramer called Morgan's recommendation "timely" and "bold," predicting the stock will quickly reach the target.

"It's not a medical marijuana stock. They have a novel platform. It is an epilepsy company."

Cramer warned investors to stay away from other marijuana-related penny stocks. "Forget it! If you like cannabis, and I'm not necessarily speaking about 'liking' cannabis, it's GW Pharma."

