The Federal Trade Commission will sue pharmacy benefit management companies over drug prices, including insulin, according to a source.

The Federal Trade Commission plans to sue three large U.S. health care companies over their practices as middlemen negotiating prices for drugs like insulin, with the agency alleging they drive up costs for patients, a person familiar with the matter told CNBC on Wednesday.

The lawsuits are expected to target the three largest companies that manage so-called pharmacy benefits, United Health Group's Optum Rx, CVS HealthCaremark Brand SignaThe person said the company is Express Scripts, a subsidiary of S Express, confirming a previous Wall Street Journal report on Wednesday about the agency’s plans. All three companies are owned or affiliated with health insurers.

The lawsuits will focus particularly on business practices related to discounts that pharmacy benefit managers (PBMs) give to drugmakers, the newspaper reported, citing people familiar with the matter.

A CVS Caremark spokesperson said in a statement Wednesday that the company is “proud of the work we have done to make insulin more affordable for all Americans with diabetes, and we stand by our record of protecting American businesses, unions and patients from rising prescription drug prices.”

“The prices of insulin and other medications are set by their manufacturers, who have repeatedly raised their prices,” an Express Scripts spokesperson said. Express Scripts works to “combat high drug industry prices and reduce the cost of thousands of medications for patients and their health plans, and the data shows we’re succeeding,” the spokesperson added.

An Optum Rx spokesperson did not immediately respond to a request for comment.

The Federal Trade Commission declined to comment on the lawsuits.

Pharmacy benefit managers are at the heart of the U.S. drug supply chain. They negotiate discounts with drug manufacturers on behalf of insurance companies, large employers, and others. They also create lists of drugs — or formularies — that insurance covers and reimburse pharmacies for prescriptions.

The Federal Trade Commission has been investigating pharmacy benefit management companies since 2022. The insulin pricing probe is also examining drug companies, but it’s unclear whether they will be named in upcoming lawsuits, Politico reported, citing people familiar with the matter. Eli LillyFrench pharmaceutical company Sanofi Danish pharmaceutical company Novo Nordisk The company controls nearly 90% of the U.S. insulin market.

The Federal Trade Commission on Tuesday released a scathing interim report based on its ongoing investigation into drug benefit management companies. The report accuses the three largest drug benefit management companies of manipulating the drug supply chain to enrich themselves at the expense of smaller independent pharmacies and patients in the United States.

The Federal Trade Commission report said that six of the largest pharmacy benefit management companies handled nearly 95 percent of the prescriptions filled in the United States.

Pharmacy benefit managers claim that manufacturers are responsible for high drug prices, while drugmakers say that discounts and fees collected by these middlemen force them to increase prices on listed products.

The Biden administration and Congress have stepped up pressure on pharmacy benefit managers, seeking greater transparency in their operations as many Americans struggle to afford prescription drugs. On average, Americans pay two to three times more for prescription drugs than patients in other developed countries, according to a White House fact sheet.

The Inflation Reduction Act signed by President Joe Biden capped insulin prices for Medicare beneficiaries at $35 per month. This policy currently does not cover patients with private insurance.