Disclosed are pyridazine derivatives represented by Formula I or pharmaceutically acceptable salts or hydrates thereof, pharmaceutical compositions comprising the compounds, methods of treating and/or preventing diseases or disorders associated with viral infections in patients using the compounds, and the use of the compounds in preparing the medicaments for treating and/or preventing diseases or disorders associated with viral infections. The compounds represented by Formula I have antiviral activity, especially anti-microRNA viral activity. Symbols in the compounds represented are described in the specification.