Nucleoside chemical compounds, which interact with specific structures of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) are disclosed. The compounds interfere with the activities of telomerase and reverse transcriptase, and are useful as antivirals, antibacterials and anticancer agents. Methods of treating or preventing cancers in patients involving administration of a therapeutically effective amount of a composition having an inhibitor or antagonist of the reverse transcriptases (RTs) expressed in cells of the patients are also disclosed. Method of using nucleoside analogs and other inhibitors of RTs in conjunction with DNA damaging agents such as genotoxic agents or radiation or photodynamic therapy or combinations these for the treatment of various cancers are also disclosed.
