Used in the treatment of chronic hepatitis C virus (HCV) infection, particularly genotypes 1 and 4. It is a component of combination antiviral therapy that works by inhibiting the HCV NS5A protein, which is essential for viral replication. The acetone solvate form helps improve stability and manufacturability of the drug product. Commonly formulated with sofosbuvir in fixed-dose tablets, this combination offers high cure rates with shorter treatment durations and fewer side effects compared to older regimens. Effective in both treatment-naïve patients and those who have failed prior therapies.