Lipophilic Triphosphate Prodrugs of Various Nucleoside Analogues.

The antiviral efficacy of many nucleoside analogues is strongly dependent on their intracellular activation by host cellular kinases to yield ultimately the bioactive nucleoside analogue triphosphates (NTP). The metabolic conversion of nucleoside analogues into their triphosphates often proceeds insufficiently. We developed a nucleoside triphosphate (NTP) delivery system (the Triro approach), in which the γ-phosphate is covalently modified by two different biodegradable masking units, one is the acyloxybenzyl (AB) moiety and the other is the alkoxycarbonyloxybenzyl (ACB) group. Such compounds formed NTPs with high selectivity by an enzyme-triggered mechanism in human T-lymphocyte CEM cell extracts loosing first the AB moiety, followed by the ACB group. This enables the bypass of all steps of the intracellular phosphorylation. This approach was applied here to convert some modestly active or even inactive nucleoside analogues into powerful biologically active metabolites. Potent antiviral activity profiles were obtained depending on the lipophilicity of the Triro-NTP prodrugs against HIV-1 and HIV-2 replication in cultures of infected wild-type CD4 CEM T-cells and more importantly in thymidine kinase-deficient CD4 T-cells (CEM/TK). This Triro strategy offers high potential for future antiviral and antitumoral chemotherapies.