Pharmaceutical giant AbbVie (NYSE:ABBV) has won U.S. antitrust approval for its purchase of Allergan (NYSE:AGN) for $63 billion in cash and stock. The purchase is seen as a hedge against the impending expiration of U.S. patents on AbbVie’s blockbuster drug, Humira. North Chicago-based AbbVie announced the deal in June 2019, but ran up against U.S. Federal Trade Commission…