The present invention relates to new Fused Tricyclic Silyl Compounds of Formula (I): (I) and pharmaceutically acceptable salts thereof, wherein A, B, C, D, M1, X1 and X2 are as defined in present document The present invention also relates to compositions comprising at least one Fused Tricyclic Silyl Compound, and methods of using the Fused Tricyclic Silyl Compounds to treat or prevent an HCV infection in a patient.