(CNBC) – CVS Health, UnitedHealth Group and Cigna sued the Federal Trade Commission on Tuesday, claiming that the agency’s case against drug supply chain middlemen over high insulin prices in the U.S. is unconstitutional.

The complaint, filed in the U.S. District Court for the Eastern District of Missouri, is the latest move in a bitter legal fight between the three largest pharmacy benefit managers, or PBMs, in the U.S. and the FTC. (Read More)