Anthem’s offer for smaller rival Cigna is part of a daisy chain of potential deals in the health insurance sector. Cigna Chairman Isaiah Harris, Jr. and Chief Executive David Cordani wrote a letter to Anthem’s board outlining reasons why the company was rejecting Anthem’s stock and cash offer. Anthem, the second-largest U.S. health insurer, said in a statement on Saturday that had made four offers for Cigna in June.