Telaprevir (marketed under the brand names Incivek and Incivo) is a direct-acting antiviralagent against the hepatitis C virus (HCV). It is a hepatitis C virus NS3/4A protease inhibitor indicated for the treatment of genotype 1 chronic hepatitis C (CHC) in adult patients with compensated liver disease, including cirrhosis, who are treatment-naïve or who have been previously treated with interferon-based treatment, including prior null responders, partial responders, and relapsers in combination with peginterferon alfa and ribavirin. Telaprevir is not used as a monotherapy. It is necessary for the proteolytic cleavage of the HCV encoded polyprotein into mature forms of the NS4A, NS4B, NS5A and NS5B proteins and essential for viral replication. It belongs to the chemical class of alpha-ketoamids and binds to NS3/4A in a covalent but reversible manner.