The present invention is directed to compounds of formulae (I) and (II) and pharmaceutically acceptable forms thereof; pharmaceutical compositions thereof; and methods of treating a viral infection, such as a hepatitis C virus (HCV) infection, by administering to a subject diagnosed with or being susceptible to the viral infection a compound of formulae (I) and (II), a pharmaceutically acceptable form thereof, or a pharmaceutical composition thereof. The present invention is also directed to high-throughput methods of identifying compounds able to modulate hepatitis C virus (HCV) replication activity.