Prodrugs activated by rna-dependent dna-polymerases

The present invention relates to the field of compounds useful as prodrugs, and in particular prodrugs activated in cancer cells and in cells infected by retroviruses, by DNA-polymerising enzymes, which use a RNA molecule as template, such as human telomerase and HIV reverse transcriptase. STATE OF ART At present the therapeutic treatment of cancer and retrovirus-caused pathologies is strongly limited in its effectiveness due to the low selectivity of the drugs used for cancer cells and for retrovirally infected cells. Both neoplastic transformation and retroviral infection do not transform cells in such a way that after phenotypic change they can easily become a selective target for drugs. Cancer pharmacology, for example, is still based on cytotoxic drugs that are highly harmful also for the healthy cells of the individual, while anti-AIDS drugs have serious side effects mostly due to their interference with the normal physiology of non-infected cells. [0004] This lack of selectivity of anticancer and antiretroviral drugs is the cause of their high toxicity in vivo. Moreover in the case of cancer such unwanted secondary effects are not compensated by a long-lasting satisfying remission, especially in cases of advanced solid tumours, which still represent an incurable disease with survival chances tending, in the long term, to zero. It would therefore be good to have more selective antiretroviral and anticancer agents, both to minimise the side effects and to increase their effectiveness and therapeutic index. In recent years attempts have been made to administrate cytotoxic drugs as "prodrugs". From a therapeutic point of view "prodrug" is an inactive compound, which can be transformed in vivo into an active drug, i.e. into a compound therapeutically active, thanks to chemical or enzymatic transformations of its structure. The difficulty in providing a good prodrug does not only lie in finding a molecule able to activate in vivo, but also in making this activation highly selective for the target cells. In other words, the ideal candidate anticancer or antiretroviral prodrug is that activating into drug, exerting thereby a cytotoxic action that kills the infected or cancer cells only after having reached them, remaining stable and inactive in the healthy tissues.