Shares of companies owning pharmacy benefit managers fell on Wednesday after the introduction of a bipartisan bill that would force health insurers or drug middlemen to divest their pharmacy businesses.CVS Health’s Caremark, Cigna’s Express Scripts and UnitedHealth Group’s Optum control the majority of pharmacy benefit management (PBMs) in the US, while their parent companies also operate health insurance businesses.Shares of all three companies were down between 4.8% to 5.5% after the Wall Street Journal f ...