In a Monday press conference at his Mar-a-Lago resort in Palm Beach, Fla., Trump criticized pharmacy benefit managers (PBMs), who negotiate drug prices between drug makers and insurance companies, calling them “middlemen” who make more money than drug companies. He lamented the high prices of U.S. drugs, which are 2.78 times as expensive as 33 other countries, according to February data from policy think tank RAND Institute.

“We’re going to knock out the middleman,” Trump said during the press conference. “We’re going to get drug costs down at levels that nobody has ever seen before.

“I don’t know who these middlemen are, but they are rich as hell,” he added.

Trump’s comments had an almost immediate effect on the respective parent companies behind Caremark, Optum, and Express Scripts, the three of which make up nearly 60% of the market share of pharmacy benefit managers. Share prices of CVS Health faltered about 1% overnight following the press conference, while UnitedHealth Group’s dropped about 2.5%, and Cigna’s fell more than 4.5%.

Investors’ reaction to Trump’s press conference is another example of the president-elect’s influence on the stock market, even before he returns to the Oval Office next year. Following news of Trump’s plan to appoint vaccine skeptic Robert F. Kennedy Jr. to head of the Department of Health and Human Services, vaccine makers saw a $8 billion hit to their market capitalizations overnight; Moderna’s stock dropped 5% following Trump’s decision, and Novavax fell 7%.

The debate over pharmacy benefit managers

PBMs’ presence remains a sticky subject in the health care world. These third-party companies claim they are often able to lower drug prices for patients by negotiating the presence of drugs on coverage lists, which by extension gives drug companies greater market access. Though Trump claimed pharmacy benefit managers make more money than drug companies, research from the University of Southern California’s Schaeffer Center for Health Policy & Economics found that gross margins for drug companies average about 71% compared to only 6% for pharmacy benefit managers. 

“Any policy that limits the use of PBM negotiating tools would leave American patients, taxpayers, and businesses at the mercy of the prices drugmakers set,” a CVS Caremark spokesperson told Fortune in a statement. “We welcome additional engagement with any federal or state official interested in learning more about the value we deliver.”

The Pharmaceutical Care Management Association, whose members include many major pharmacy benefit managers, said in a statement it looks forward to working with the Trump administration to lower drug prices.  

“Whether it’s through negotiations to lower costs, partnerships with pharmacies, or clinical care programs, our value is in helping patients conveniently, safely, and affordably access prescription drugs,” the statement said.

But how pharmacy benefit managers are able to negotiate the prices of drugs are shrouded in secrecy. The Federal Trade commission filed a lawsuit against the three largest pharmacy benefit managers in September, alleging they artificially inflating profits by limiting access to more affordable insulin medications and instead guiding them toward more expensive options. The House Committee on Oversight and Accountability released a report in July arguing intermediaries essentially operate in a black box to increase prices or overcharge patients.

Although billionaire investor Mark Cuban frequently butts heads with Trump, he aligns with the president-elect’s stance on cutting out middlemen to lower drug prices. In January 2022, he launched Cost Plug Drugs as an online pharmacy selling generic drugs that discloses price markups, shipping costs, and other fees.

“It’s impossible to find the price of a drug,” Cuban said in a presentation at the University of Pennsylvania Leonard Davis Institute of Health Economics last week. “I don’t mean that they make it too hard to find. I mean, you simply cannot find the price or cost of drugs.”