CVS Health has denied coverage for a new HIV prevention drug despite it being nearly 100 percent effective, citing in part the medication’s high cost.

The nation’s largest pharmacy benefit manager will not cover Gilead’s Yeztugo, generic name lenacapavir (LEN), neither through its commercial plans nor the Affordable Care Act. CVS spokesperson David Whitrap told Reuters that the decision was based on “clinical, financial, and regulatory factors.”

Gilead is still negotiating the price with CVS, other sources told the outlet, which currently sits at over $28,000 annually. Gilead said that it has not had issues with other pharmacy benefit managers, and that it is still on track to reach 75 percent U.S. insurer coverage by the end of the year and 90 percent coverage by June next year.

“CVS Health’s decision is a clear violation of the ACA’s requirement to cover USPSTF-recommended preventive services, including PrEP,” Carl Schmid, executive director of the HIV+Hepatitis Policy Institute, said in a statement. “The entire world is excited by this drug and its potential contribution to preventing and eventually ending HIV. However, a drug will only work if people can access it and right now CVS Health, which owns the largest pharmacy benefit manager in the country, is shamefully blocking people from taking it, unlike other payers.” {read}