April 2 (Reuters) - The Federal Trade Commission put on hold a lawsuit against pharmacy-benefit manager $(PBM)$ units of UnitedHealth UNH.N, Cigna CI.N and CVS Health CVS.N over insulin prices after the Trump administration fired two of the agency's commissioners.

The two Democratic commissioners, Alvaro Bedoya and Rebecca Kelly Slaughter, who had voted in favor of the lawsuit against the PBMs, were fired last month.

In court filings this week, the FTC said the case will be put on hold for 105 days, as there were no sitting commissioners available to participate.

Of its five sitting commissioners, two were fired, two removed from the case, and one resigned when Trump took office.

The FTC lawsuit accuses the PBMs of unfairly limiting access to insulin drugs with lower list prices and steering diabetes patients towards higher priced insulin in order to reap millions of dollars in rebates from pharmaceutical companies.

"CVS Health is confident the facts are on our side – drugmakers alone set the price of insulin – and we will continue to defend the case vigorously to protect our ability to make insulin affordable for American businesses and their members," David Whitrap, vice president, External Affairs at CVS, told Reuters in a statement.

UnitedHealth and Cigna did not immediately respond to Reuters' requests for comment.

The three companies own the country's largest PBMs - Caremark, Optum and Express Scripts.

PBMs act as middlemen between drug companies and consumers. They negotiate volume discounts and fees with drug manufacturers on behalf of employers and health plans, create lists of medications that are covered by insurance, and reimburse pharmacies for prescriptions.

Bedoya and Slaughter sued U.S. President Donald Trump last month saying their removals violated federal law and a 90-year-old U.S. Supreme Court precedent upholding agency independence.

(Reporting by Puyaan Singh in Bengaluru; Editing by Shinjini Ganguli)

((Puyaan.Singh@thomsonreuters.com;))