The FTC’s complaint accuses Optum Rx and other pharmacy benefit managers of “abusing their economic power." Optum called the move a "baseless action."

Regulators say the nation's largest pharmacy benefit managers are partly to blame for the soaring cost of insulin in the U.S.

The Federal Trade Commission took action Friday against the three largest pharmacy benefit managers, accusing the companies of “engaging in anticompetitive and unfair rebating practices that have artificially inflated the list price of insulin drugs,

FTC Sues Prescription Drug Middlemen for Artificially Inflating Insulin Drug Prices – Includes Caremark, Express Scripts, Optum and Affiliates

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

The FTC suit targets the three biggest so-called pharmacy benefit managers, UnitedHealth Group's Optum Rx, CVS Health's Caremark and Cigna's Express Scripts.