Health care stocks fall as lawmakers, patients push for changes in their business models.

Shares of major health care companies fell as much as 5 percent on Wednesday as investors worried that pressure from lawmakers and patients could force changes to their business models.

Falling stocks include United Health Group, sign And CVS Healthwho run the nation’s three largest private health insurance and drug supply chain middlemen known as pharmacy benefit managers, or PBMs. He also owns a pharmacy business. Shares of all three companies were down at least 4.8 percent in early afternoon trade.

The stock reaction on Wednesday appeared to be in response. New bipartisan legislation Aimed at breaking up PBMs, which was First reported by The Wall Street Journal. PBMs have faced years of scrutiny from Congress and the Federal Trade Commission over allegations that they raise drug prices to boost patient profits.

The moves in the shares also come as insurance companies and their practices have subsequently faced public criticism. The fatal shooting of Brian ThompsonCEO of UnitedHealth Group’s insurance arm, last week. Health stocks had already fallen in the days following Thompson’s murder.

The Journal reported that a Senate bill, sponsored by Sens. Elizabeth Warren, D-Mass., and Josh Hawley, R-Mo., that owns health insurance companies, or PBMs, within three years of their will force the separation of the pharmacy business. A companion bill is scheduled to be introduced in the House on Wednesday, lawmakers told the Journal.

“PBMs have manipulated the market to enrich themselves — raising drug prices, defrauding employers, and putting small pharmacies out of business,” Warren said in a release. said “My new bipartisan bill would eliminate these conflicts of interest by reining in these brokers.”

Healthcare companies that own both PBMs and pharmacies, the release added, “have a gross conflict of interest that enables these companies to enrich themselves at the expense of patients and independent pharmacies. ”

The largest PBMs — UnitedHealth Group’s Optum Rx, CVS Health’s Caremark and Cigna’s Express Scripts — are all owned or affiliated with health insurers. According to the FTC, they administer about 80% of the nation’s prescriptions as a whole.

PBMs sit at the heart of the drug supply chain in the U.S., negotiating rebates with drug manufacturers on behalf of insurers, large employers and federal health plans. They also create lists of drugs, or formularies, that are covered by insurance and reimburse pharmacies for prescriptions.

The FTC has been investigating PBMs since 2022.

— CNBC’s Bertha Coombs contributed to this report.