Whether Express Scripts wins its unique defamation lawsuit will depend on whether the PBM can prove the FTC made false statements. But winning the lawsuit may not be what the PBM is looking for.

Cigna's Express Scripts filed a lawsuit Tuesday challenging a federal report that places the blame for rising drug prices on pharmacy benefit managers, describing it as "seventy-four pages of unsupported innuendo" and calling for a retraction.

As the FTC has increasingly prodded PBMs over their role in high drug costs, Express Scripts is fighting back by launching a lawsuit against the agency.