CHICAGO, May 29 (Reuters) - Express Scripts and several

of its affiliated pharmacies filed a lawsuit on Thursday asking

an Arkansas federal judge to overturn a state law set to go into

effect next year that would ban pharmacy benefit managers from

owning pharmacies.

The lawsuit, filed in the U.S. District Court for the

Eastern District of Arkansas, says the law puts an

unconstitutional restriction on interstate commerce by burdening

out-of-state companies like Express Scripts, which is based in

St. Louis.

Express, one of the nation's largest pharmacy benefit

managers, seeks a declaration that the law is unconstitutional

and an order barring its enforcement.

Sam Dubke, a spokesperson for Arkansas Governor Sara

Huckabee Sanders, who signed the law in April, said in a

statement, "these big drug middlemen are only attacking Arkansas

in the courts because they're worried other states will join

Governor Sanders in fighting for patient access and affordable

prescriptions."

The lawsuit names the members of the Arkansas State Board of

Pharmacy, which regulates the state's pharmacies.

In a statement, Express Scripts, which is a unit of the

Cigna Group ( CI ), said the law will likely force it to close

some retail pharmacies and bar it from mailing prescriptions to

thousands of Arkansas residents through its mail-order pharmacy

business.

"While Arkansas politicians claim this law was designed to

lower drug prices and increase access to medications, it will do

just the opposite," said Andrea Nelson, Cigna's ( CI ) chief legal

officer.

Pharmacy benefit managers serve as intermediaries,

negotiating prescription drug prices with drugmakers on behalf

of employers and health plans. They also often manage pharmacy

networks and operate mail-order pharmacies.

Arkansas' law, which is set to go into effect in January,

bars PBMs from receiving permits to dispense prescription

medication and revokes PBMs' existing permits, according to the

legislation.

The law is meant to cut down on anticompetitive behavior by

the PBMs, which set the prices for the drugs they dispense

through their pharmacies, according to the governor's office.

Their business practices have drawn increasing scrutiny in

recent years from U.S. lawmakers looking to lower drug prices,

and from the Federal Trade Commission, which accused the three

largest PBMs of driving up the cost of insulin drugs.

(Additional reporting by Amina Niasse in New York; Editing by

Leigh Jones and Bill Berkrot)