Attorney General Dave Yost is suing pharmacy benefits managers saying they are illegally driving up drug prices.

Yost filed the lawsuit on Monday, and it said Express Scripts and Prime Therapeutics used a Switzerland-based company to hike up prices and push those higher costs onto patients.

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In addition to the price hikes, Yost says the companies fail to live up to promises to negotiate lower prices from manufacturers.

As of this reporting, none of the companies have responded to the lawsuit.

Co-defendants listed in Yost’s lawsuit include Cigna Group (the parent company of Express Scripts,) Evernorth Health (another subsidiary of Cigna,) and Humana (the parent company of Humana Pharmacy Solutions.)

“Medications shouldn’t cost an arm and a leg, metaphorically or literally,” the attorney general said. “Insulin is just a symptom of the problem; PBMs are the disease.”