(Bloomberg) -- CVS Health Corp. shares fell after the company gave preliminary 2027 profit guidance that disappointed investors and warned of challenges in its pharmacy benefit manager next year, overshadowing a better-than-expected second quarter report. Shares fell as much as 10.4% when markets opened in New York, reversing earlier pre-market gains that were based on a rosy second quarter and raise to the 2026 guidance. Several US health insurance companies have boosted plans' prices, cut benefits, and left money-losing markets in order to increase profits. Investors have been closely watching the performance of private Medicare plans, a business that's historically driven profits but struggled more recently under government scrutiny. CVS reported adjusted operating income above Wall Street's expectations in its health insurance, retail pharmacy, and pharmacy benefits management segments.