The present invention relates to novel Fused Tetracyclic Heterocyclic Compounds of Formula I: (I), wherein A, A′, R2A, R2B, R7, R8, R9, and R10 are defined herein. The compounds and their pharmaceutically acceptable salts are useful for the prophylaxis or treatment of infection by HCV and the prophylaxis, treatment, or delay in the onset of disease caused by HCV. The present invention also relates to pharmaceutical compositions comprising at least one Fused Tetracyclic Heterocyclic Compound, optionally in combination with other antivirals, immunomodulators, antibiotics or vaccines, and methods of using the Fused Tetracyclic Heterocyclic Compounds for treating or preventing HCV infection in a patient.