γ-Ketobenzyl-Modified Nucleoside Triphosphate Prodrugs as Potential Antivirals
Tobias Nack, Thiago Dinis de Oliveira, Stefan Weber, Dominique Schols, Jan Balzarini, Chris Meier
Abstract
The antiviral activity of nucleoside reverse transcriptase inhibitors is often hampered by insufficient phosphorylation. Nucleoside triphosphate analogues are presented, in which the γ-phosphate was covalently modified by a non-bioreversible, lipophilic 4-alkylketobenzyl moiety. Interestingly, primer extension assays using human immunodeficiency virus reverse transcriptase (HIV-RT) and three DNA-polymerases showed a high selectivity of these γ-modified nucleoside triphosphates to act as substrates for HIV-RT, while they proved to be nonsubstrates for DNA-polymerases α, β, and γ. In contrast to d4TTP, the γ-modified d4TTPs showed a high resistance toward dephosphorylation in cell extracts. A series of acyloxybenzyl-prodrugs of these γ-ketobenzyl nucleoside triphosphates was prepared. The aim was the intracellular delivery of a stable γ-modified nucleoside triphosphate to increase the selectivity of such compounds to act in infected versus noninfected cells. Delivery of γ-ketobenzyl-d4TTPs was proven in T-lymphocyte cell extracts. The prodrugs were potent inhibitors of HIV-1/2 in cultures of infected CEM/0 cells and more importantly in thymidine kinase-deficient CD4+ T-cells.