The owner of the United States' largest pharmacy benefit manager (PBM) is declining to cover Gilead Sciences’ long-acting HIV prevention breakthrough, at least for now. | CVS Health, the parent of PBM juggernaut CVS Caremark,

Shares of Gilead Sciences, Inc. (GILD) tumbled 2.2% on Aug. 21, after pharmacy benefit manager CVS Health (CVS) decided not to add the former’s new HIV prevention drug, Yeztugo (lenacapavir), to its commercial plans for now.

CVS Health , which runs the largest U.S. pharmacy benefit manager, will not add Gilead Sciences' new HIV prevention drug to its commercial plans for now, a spokesperson told Reuters, despite the medicine's proven effectiveness.