One very expensive prescription drug threatened to financially cripple an entire city. Rather than using a health insurance company, Rockford, [Illinois] has, for years, paid its own health care costs for its 1,000 employees and their dependents. When Rockford got hit with the drug bill it was so enormous the mayor at the time set out to understand why. In 2015, two small children of Rockford employees were treated with Acthar, a drug that's been on the market since 1952. In 2001, Acthar sold for about $40 a vial. Today: more than $40,000. [Rockford Mayor Larry Morrissey] wanted to know how that could've happened. His investigation got nowhere until last year, when the Federal Trade Commission charged the drug manufacturer, Mallinckrodt, with violating antitrust laws. [The company] bought another drug that was Acthar's main competitor ... and put it on the shelf. Many of the doctors who prescribed a lot of Acthar also were getting money from the company that makes Acthar ... adding up to huge sums. Cities like Rockford [hire pharmacy benefit managers or PBMs] to negotiate down the price of drugs. The company negotiating prices for Rockford is Express Scripts. Express Scripts is many companies, not just the PBM. It also owns a pharmacy that sells expensive drugs, [as well as] a company that ships and packs expensive drugs. The city of Rockford was able to find out one more piece of the puzzle: that Express Scripts ... had a contract to be the exclusive distributor of Acthar.