Pharmacy benefit manager Express Scripts sued the U.S. Federal Trade Commission on Tuesday over the regulator's recent drug pricing report, calling the report's conclusion that the prescription middlemen raise drug costs defamatory.

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

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