(Reuters) - Shares of health insurers such as UnitedHealth and CVS Health fell on Wednesday after a Wall Street Journal report said a bipartisan group of lawmakers was set to introduce legislation to break up pharmacy-benefit managers.

The Senate bill, sponsored by U.S. Senators Elizabeth Warren and Josh Hawley, will force companies that own health insurers or pharmacy-benefit managers to divest their businesses operating pharmacies within three years, the report said.

Pharmacy-benefit managers negotiate prescription drug prices between insurers, pharmacies and drugmakers, and directly reimburse pharmacies for prescription drugs included under their agreed upon terms.

UnitedHealth shares fell 5%, while CVS Health dropped 4.3% and Cigna slipped 4.4%.

Peers Elevance, Humana and Centene fell between 1% and 3%.

Shares of insurers have come under pressure after Brian Thompson, the CEO of UnitedHealth's health insurance unit, was fatally shot outside a Manhattan hotel last week. (This story has been refiled to fix a grammatical error in paragraph 1)

(Reporting by Sriparna Roy in Bengaluru; Editing by Devika Syamnath)