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.

CVS Health will not cover Gilead's Yeztugo, generic name lenacapavir (LEN), citing "clinical, financial, and regulatory factors."

Executives at Gilead Sciences, the biotech behind a long list of HIV treatments and preventative medicines, have spoken with great optimism in recent weeks about the prospects that insurers will cover Yeztugo,