Six former executives and managers at Insys Therapeutics Inc. were arrested on Thursday and charged with conspiring to defraud health insurers and bribe doctors in exchange for prescribing the company’s fentanyl painkiller, Subsys, the Justice Department said.

Among those arrested were former Chief Executive Michael Babich, who resigned from the company in November 2015. Mr. Babich, 40 years old, was charged with conspiracy to commit racketeering, conspiracy to commit wire and mail fraud, and conspiracy to violate the anti-kickback...