THE PRESENT INVENTION RELATES TO A COMPOUND REPRESENTED BY THE FOLLOWING FORMULA [I] WHEREIN EACH SYMBOL IS AS DEFINED IN THE SPECIFICATION, OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF, OR A SOLVATE THEREOF AND AN ANTI-HCV AGENT AND AN HCV POLYMERASE INHIBITOR CONTAINING THIS COMPOUND. THE COMPOUND OF THE PRESENT INVENTION SHOWS AN ANTI-HCV ACTIVITY BASED ON THE HCV POLYMERASE INHIBITORY ACTIVITY, AND USEFUL AS AN AGENT FOR THE PROPHYLAXIS OR TREATMENT OF HEPATITIS C.