UnitedHealth Group, the largest U.S. health insurer, has chosen to back the Gilead Sciences hepatitis C virus (HCV) combo drug Harvoni (sofosbuvir/ledipasvir) as its preferred HCV treatment, Reuters reports.

UnitedHealth’s move is the latest in an ongoing hep C drug price competition between Gilead and AbbVie, in which both pharmaceutical companies are offering extensive discounts to insurers in exchange for exclusive coverage on their drug formularies.

Before discounts, Gilead’s once-a-day Harvoni regimen costs $93,400 for a 12-week treatment. AbbVie’s new multiple-dose hep C drug Viekira Pak (ombitasvir/paritaprevir/ritonavir) costs $83,319 for the same treatment length. Analysts say both drugs are being offered to pharmacy benefits managers at a discount of 30 to 40 percent.

UnitedHealth is the last of the top three U.S. health insurers to strike a hep C deal. So far, Aetna, Anthem and Humana have backed Gilead’s treatments, as has pharmacy benefit manager CVS Health. ExpressScripts and the state of Missouri have chosen AbbVie’s Viekira Pak as their drug of choice. Prime Therapeutics has given priority to both.

UnitedHealth’s priority list applies to all of the company’s commercial customers using its Optum RX pharmacy benefits manager program. It also applies to a number of self-insured customers, such as large employers, that follow its formularies, as well as several Medicaid, Medicare and military contracts.