Structure−Activity Relationship of Heterobase-Modified 2‘-C-Methyl Ribonucleosides as Inhibitors of Hepatitis C Virus RNA Replication

Abstract

Hepatitis C virus infection constitutes a significant health problem in need of more effective therapies. We have recently identified 2'-C-methyladenosine and 2'-C-methylguanosine as potent nucleoside inhibitors of HCV RNA replication in vitro. However, both of these compounds suffered from significant limitations. 2'-C-Methyladenosine was found to be susceptible to enzymatic conversions by adenosine deaminase and purine nucleoside phosphorylase, and it displayed limited oral bioavailability in the rat. 2'-C-Methylguanosine, on the other hand, was neither efficiently taken up in cells nor phosphorylated well. As part of an attempt to address these limitations, we now report upon the synthesis and evaluation of a series of heterobase-modified 2'-C-methyl ribonucleosides. The structure-activity relationship within this series of nucleosides reveals 4-amino-7-(2-C-methyl-beta-d-ribofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine and 4-amino-5-fluoro-7-(2-C-methyl-beta-d-ribofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine as potent and noncytotoxic inhibitors of HCV RNA replication. Both 4-amino-7-(2-C-methyl-beta-d-ribofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine and 4-amino-5-fluoro-7-(2-C-methyl-beta-d-ribofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine display improved enzymatic stability profiles as compared to that of 2'-C-methyladenosine. Consistent with these observations, the most potent compound, 4-amino-5-fluoro-7H-pyrrolo[2,3-d]pyrimidine ribonucleoside, is orally bioavailable in the rat. Together, the potency of the 2'-C-methyl-4-amino-pyrrolo[2,3-d]pyrimidine ribonucleosides and their improved pharmacokinetic properties relative to that of 2'-C-methyladenosine suggests that this class of compounds may have clinical utility.

Antiviral screening identifies adenosine analogs targeting the endogenous dsRNALeishmaniaRNA virus 1 (LRV1) pathogenicity factor

“…The EC 50 measured using dsRNA or capsid levels were similar, with that of the dsRNA being somewhat less, consistent with the anticipated mode of action targeting the RDRP and genome replication. Both compounds have demonstrated activity against HCV, where they target the viral RDRP by chain termination (37,38,49). By molecular modeling of the L. guyanensis LRV1 RDRP domain against other RDRPs, such as HCV, we were able to generate a view of the active site including residues putatively binding to the nucleotide substrates (Fig.…”

“…There are now ample data suggesting that LRV1 contributes to the severity in human leishmaniasis (6,13,17,19,20,55), suggesting that anti-LRV1 inhibitors could be clinically useful, alone or in conjunction with existing antileishmanials. Unfortunately, pharmacokinetic studies of the two compounds studied here in mammals suggest that neither of these are good candidates for testing of this hypothesis just yet, as the concentration needed for LRV1 elimination (10 μM) is above the maximum achievable serum concentration in various mammalian models, typically less than 1 μM (38,49,56). Thus, future efforts must focus on the development of compounds with higher potency targeting LRV1, without significant human host toxicity.…”

Mutations Conferring Resistance to a Hepatitis C Virus (HCV) RNA-Dependent RNA Polymerase Inhibitor Alone or in Combination with an HCV Serine Protease Inhibitor In Vitro

“…1, Shire, 2), the nucleoside 2-(4-amino-pyrrolo [2,3- (Fig. 1, BILN-2061, 5), were synthesized according to procedures described previously (3,6,16,30). Recombinant IFN-␣ was purchased from PBL Biomedical Laboratories, Piscataway, NJ.…”

“…These polymerase inhibitors included two nonnucleoside (thiophene amide and diamide derivatives discovered by Shire and Boehringer Ingelheim, respectively) and one nucleoside (published by Merck) inhibitors (6,16,30). The IC 50 values for Shire-thiophene amide, Boehringer Ingelheim-diamide, and Merck-nucleoside were 0.35, 1.97, and 0.27 M, respectively, which are 68-to 492-fold less potent than A-782759 (0.004 M) in this transient-transfection assay (Table 5).…”

A New Paradigm for Developing Antiviral Drugs Exemplified by the Development of Supremely High Anti-HIV Active EFdA

“…The indication was confirmed first by Yang and his co-workers using Ed4T and X-ray crystallographic method [39]. They showed that the 4'-C-ethynyl group fits into a hydrophobic MAGI = multinuclear activation of galactosesidase indicator, HIV = human immune deficiency virus, AZT = 3'-azido-3'-deoxythymidine; 3TC = 2',3'-dideoxy-3'-thia-Lcytidime; d4T = 2',3'-didehydrodideoxythymidine.…”