Shares of CVS Health Corp ( CVS ) , Cigna Group ( CI ) and UnitedHealth Group Inc ( UNH ) are falling Monday afternoon after President-elect Donald Trump said he plans to target Pharmacy-benefit managers (PBMs) during his administration.

What Happened: According to a Bloomberg report, Trump on Monday sent shares of PBMs lower when he said he plans to “knock out” PBMs, or so-called drug middlemen, from the industry.

CVS Health’s Caremark, Cigna’s Express Scripts and UnitedHealth’s OptumRx are the three largest PBMs. The companies have faced repeated criticism for driving up the prices of drugs.

"We have a thing called the middleman," Trump reportedly told reporters on Monday.

"You know the middleman, right? The horrible middleman that makes more money frankly than the drug companies, and they don't do anything except they're a middleman," he said. "We're going to knock out the middleman."

The news comes after Sen. Elizabeth Warren (D.-Mass.) and Sen. Josh Hawley (R.-Mo.) unveiled a new bipartisan Senate bill last week that would require the companies that own PBMs to divest those businesses within three years.

“PBMs have manipulated the market to enrich themselves — hiking up drug costs, cheating employers, and driving small pharmacies out of business,” Warren said.

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The proposed legislation is not expected to gain traction in Congress until next year, but comments from Trump on Monday suggest the problems with the drug industry could be addressed sooner rather than later.

The role of PBMs in the healthcare industry has been a heightened focus in recent weeks following the murder of UnitedHealthcare CEO Brian Thompson. Several dissatisfied patients have expressed dissatisfaction with PBMs since. Luigi Mangione has been charged with killing Thompson.

CVS, CI, UNH Price Action: At publication time, CVS shares were down 5.61% at $46.60, Cigna Group ( CI ) shares were down 3.05% at $272.76 and UnitedHealth ( UNH ) shares were down 4.22% at $498.50, according to Benzinga Pro.