Disclosed is a pharmaceutical composition of a hepatitis C viral protease inhibitor which is suitable for oral administration via a liquid- or semi-solid-filled capsule and methods of using this composition for inhibiting the replication of the hepatitis C virus (HCV) and for the treatment of an HCV infection. The liquid- or semi-solid pharmaceutical composition of the present invention comprises a compound of formula I, or a pharmaceutically acceptable salt thereof, together with one or more pharmaceutically acceptable lipids and hydrophilic surfactants.