Months earlier, the agency released a report alleging the companies drove up the costs of some medications, including insulin.

The Federal Trade Commission sued on Friday the three largest pharmaceutical intermediaries charged with negotiating drug prices on behalf of insurers, claiming they are illegally maximizing profits by steering patients to high-cost insulin products.

The Federal Trade Commission brought action against the three largest prescription drug benefit managers (PBMs)—Caremark Rx (a CVS company), Express Scripts (ESI), and OptumRx—and their affiliated group purchasing organizations (GPOs) for engaging in anticompetitive and unfair rebating practices that have artificially inflated the list price