Synthesis and Evaluation of ATP-Binding Site Directed Potential Inhibitors of Nucleoside Triphosphatases/ Helicases and Polymerases of Hepatitis C and other Selected Flaviviridae Viruses

Abstract

Hepatitis C virus (HCV), West Nile virus (WNV), Japanese encephalitis virus ( JEV), and dengue virus (DENV) are members of Flaviviridae. They are deadly human pathogens and new and better therapeutic strategies are desperately needed. However, there are considerable barriers to the development of anti-Flaviviridae therapeutics, including the persistence of the virus, its genetic diversity during replication in the host and, for example, in the case of HCV, the lack of reproducible infectious culture systems. Similarities in the key Flaviviridae enzymes (with respect to conserved subdomain organization and arrangement of structural motifs) may indicate the potential usefulness of ribonucleoside analogues in the treatment of these viral infections. Over the last few years our understanding of the Flaviviridae replication cycle and the key enzymes involved in it has increased, giving hope for development of new antiviral agents.The Flaviviridae genome is a positive-stranded RNA, with a single open reading frame that translates into a single polyprotein. This polyprotein is co-and post-translationally processed by cellular and viral proteases into structural and non-structural (NS) proteins (Rosenberg, 2001). Among the NS proteins, NS3 and NS5 -the major components of the so called 'replication complex' -appear to be the most promising targets for antiviral therapy because of their well-characterized enzymatic activities (Tan et al.,

West Nile virus meningoencephalitis

“…59 Inhibitors of nucleoside triphosphatase (NTPase)/helicase activities of Flaviviridae have not shown promising results against WNV in vitro. 60 IFN-2b inhibits growth of WNV in vitro and can protect BALB/c mice and golden hamsters from WNV-induced disease, although its efficacy is greatly diminished when treatments are delayed beyond 4-6 hours before viral challenge. 41,44,58 IFN-/ -receptor knockout mice have increased mortality following WNV challenge, whereas treatment of primary mouse neuronal cultures with IFN-before or after infection increased neuronal survival in dependently of the effect on WNV replication.…”

RNA helicases in infection and disease

“…212 HCV helicase activity is inhibited in vitro by recombinant antibodies, 213,214 by RNA aptamers 215,216 and by peptides. 217,218 Targeting the nucleotide binding site of HCV-NS3 has proven exceedingly difficult, 219 although nucleotide-mimicking competitive inhibitors have been identified. 220,221 Ring-expanded nucleoside and nucleotide analogs have been shown to selectively inhibit HCV, West Nile Virus, and Japanese encephalitis virus NS3 helicases in vitro without affecting the activity of a control host helicase.…”

Viral and cellular RNA helicases as antiviral targets

“…The ATP-binding site has been successfully targeted by kinase and gyrase inhibitors in which the binding site is a distinct and well-defined 'pocket' . By contrast, only weak inhibitors have been found that inhibit the HCV binding site 86 . One explanation might be that the HCV helicase NTP-binding site at the interface of domains 1 and 2 has little specificity -it binds all NTPs primarily through the phosphate, not the base, of the nucleotide.…”