 Grocery store chain Kroger Co. KR, -1.33 said Friday that it has sent insurer Cigna Corp. CI, -0.02 subsidiary Express Scripts Inc. a written notice of its plan to terminate their pharmacy provider agreement for commercial customers. Express Scripts drug pricing model is unsustainable for Kroger and consumers; access to affordable prescriptions and wellness services remains companys top priority, Kroger said in a statement. 