Ligand Pharmaceuticals (LGND) was Smart Insider's stock pick of the week after the company's Chief Executive Todd Davis bought $1 million worth of Ligand Pharmaceuticals' shares on May 9 at $105.20 apiece, raising his ownership by 6%.

Davis last bought the shares for $97.39 apiece in August, and it's "very encouraging" that the CEO is now making his "largest" purchase, Smart Insider said in a Tuesday note.

Davis' purchase is over four times "larger" than any purchase he made and follows stock price "strength," as he has an "excellent record as both a buyer and seller."

Chief Financial Officer Octavio Espinoza also purchased $156,000 worth of company shares on the same day, the note added.

This was Espinoza's first purchase of stock and a reversal from a sale at $116.37 per share two months earlier, the note said.

"This is also a notable trade," Smart Insider said.

Smart Insider ranked the stock +1, or strongly positive signal, on Wednesday.