Grazoprevir is a drug approved for the treatment of hepatitis C. It was developed by Merck and completed Phase III trials, used in combination with the NS5A replication complex inhibitor elbasvir under the trade name Zepatier, either with or without ribavirin. Grazoprevir is a second generation hepatitis C virus protease inhibitor acting at the NS3/4A protease targets. It has good activity against a range of HCV genotype variants, including some that are resistant to most currently used antiviral medications.