An Eighth Circuit panel had only a handful of questions on Wednesday for the pharmacy benefit managers accused of inflating insulin prices, though one of the judges expressed skepticism about pausing the Federal Trade Commission's in-house enforcement action on constitutional grounds.

CVS' Caremark, Cigna's Express Scripts and UnitedHealth's OptumRx units urged the appeals panel during oral arguments to reverse a lower court's refusal to issue a preliminary injunction that would block the FTC's administrative proceedings while their constitutional challenge plays out.

Daniel S. Volchok of WilmerHale, an attorney for the companies, said their overarching argument is that Congress impermissibly gave the FTC power that the Constitution assigns to the federal courts and to the president.

"With that power, the FTC is bringing coercive, highly consequential internal proceedings against private parties, proceedings in which it has, in recent years, always ruled for itself," Volchok said Wednesday.

The FTC brought the in-house case in September last year, accusing the so-called Big Three PBMs of using rebate schemes that prioritize insulin drugs with high list prices and prevent patients from accessing lower-priced drugs.

The companies' constitutional challenge targets restrictions that prevent FTC commissioners and the agency's administrative law judges from being removed by the president without cause. The case also alleges that the FTC's in-house proceedings violate the due process clause and Article III of the Constitution by allowing the commission to adjudicate private rights in an agency proceeding instead of federal court.

U.S. Circuit Judge Steven M. Colloton asked Volchok on Wednesday to discuss the requirements for a showing of harm from the constitutional violations, since the commission acknowledges that the removal restrictions are unconstitutional.

The commission has abandoned its defense of the U.S. Supreme Court's 1935 decision in Humphrey's Executor v. United States , which specifically upheld the FTC Act's removal protections for commissioners. President Donald Trump also fired the FTC's two sitting Democratic commissioners earlier this year without cause; one of them is challenging her removal in a petition to the Supreme Court.

Volchok said Wednesday that the commission is taking the position that the PBMs need to show "compensable harm" from the removal restrictions, but argued that this improperly imports remedy issues into the merits analysis. The cases the FTC relies on, he said, tell the court nothing about what's needed to obtain an injunction blocking future conduct and instead deal with retrospective relief for things that happened in the past.

U.S. Circuit Judge Bobby E. Shepherd asked Volchok if he could cite any cases where a court of appeals upheld a preliminary injunction or reversed a lower court's denial of a preliminary injunction against an ongoing agency proceeding based on a structural constitutional challenge.

Volchok pointed to the Fifth Circuit's August ruling upholding injunctions barring the National Labor Relations Board from prosecuting unfair labor practice cases against SpaceX based on removal protections for board members. But after a follow-up from the judge, Volchok acknowledged that's the only case he's aware of so far.