The chief executive officer of Valeant Pharmaceuticals, which made a $47 billion unsolicited offer for competitor Allergan Inc. on Tuesday, said during an interview on CNBC that he was "disappointed" with Allergan's so-called poison pill.

Allergan on Tuesday night said that its board of directors had adopted a one-year stockholder rights plan to give it more time to consider takeover proposals. The Valeant offer was made with Pershing Square Capital Management hedge fund, which built up a stake in the company.

"We are disappointed but on the other hand, I think this deal will get done," Valeant CEO Michael Pearson said on Wednesday.