Didanosine, a new antiretroviral drug. A review

Mononucleoside phosphorodithiolates as mononucleotide prodrugs

The synthesis and in vitro anti-HIV activity of a novel series of pronucleotides are reported. These prodrugs were characterized by a phosphorodithiolate structure, incorporating two O-pivaloyl-2-oxyethyl substituents as biolabile phosphate protections. The compounds were obtained following an original one-pot three-step procedure, involving the formation of a phosphorodithioite intermediate which is in situ oxidized. In vitro, comparative anti-HIV evaluations demonstrate that such original prodrugs are able to allow the efficient intracellular release of the corresponding 5'-mononucleotide. The pronucleotide of 2',3'-dideoxyadenosine (ddA) 3 exhibited a very potent antiretroviral effect with 50% effective concentration (EC₅₀) values in nanomolar concentration range in various cell lines. In primary monocytes/macrophages, this derivative was 500 times more potent in inhibiting HIV replication (EC₅₀ 0.23 pM) than ddA and the selectivity index of the prodrug is fifty times higher than the one of the parent nucleoside.

Antiviral drugs: present status and future prospects

1. There is a limited number of antiviral drugs available for therapy. Many investigations and new analytical techniques have unraveled the development and progression of a viral infection. Nowadays there is a good understanding of the multiplication cycle of viruses, including the human immunodeficiency virus. 2. In this article the currently available antiviral drugs are presented arranged by their mode of action that can be understood by the multiplication cycle of the virus. 3. Clinical use and side-effects are discussed as well as place in current therapy. Some attention is paid on promising investigational antivirals.