Radio Iowa: One of the nation’s leading drug molecule companies with a facility in northeast Iowa is being bought by an international investment firm. Cambrex Corp. announced Wednesday it has signed an agreement worth $2.4 billion with Permira, a private equity firm with offices in London, Tokyo, Hong Kong and New York. Cambrex owns a 45-acre site in Charles City employing 400 people and completed a $24 million expansion in April.