The present invention relates to novel Heterocycle-Substituted Tetracyclic Compounds of Formula (I): (I) and pharmaceutically acceptable salts thereof, wherein A, A′, R2 R3, R4 and R are as defined herein. The present invention also relates to compositions comprising at least one Heterocycle-Substituted Tetracyclic Compound, and methods of using the Heterocycle-Substituted Tetracyclic Compounds for treating or preventing HCV infection in a patient.