The present invention is directed to compounds, compositions and methods for treating or preventing
cancer and viral infections, in particular, HIV, HCV,
Norovirus, Saporovirus, HSV-1, HSV-2,
Dengue virus,
Yellow fever, and HBV in human patients or other animal hosts. The compounds are certain 6-substituted
purine monophosphates, and pharmaceutically acceptable, salts, prodrugs, and other derivatives thereof. In particular, the compounds show potent antiviral activity against HIV-1, HIV-2, HCV,
Norovirus, Saporovirus, HSV-1, HSV-2,
Dengue virus,
Yellow fever, and HBV.