Structure-activity relationship of heterobase-modified 2'-C-methyl ribonucleosides as inhibitors of hepatitis C virus RNA replication.

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.

A 7-deaza-adenosine analog is a potent and selective inhibitor of hepatitis C virus replication with excellent pharmacokinetic properties.

Improved treatments for chronic hepatitis C virus (HCV) infection are needed due to the suboptimal response rates and deleterious side effects associated with current treatment options. The triphosphates of 2'-C-methyl-adenosine and 2'-C-methyl-guanosine were previously shown to be potent inhibitors of the HCV RNA-dependent RNA polymerase (RdRp) that is responsible for the replication of viral RNA in cells. Here we demonstrate that the inclusion of a 7-deaza modification in a series of purine nucleoside triphosphates results in an increase in inhibitory potency against the HCV RdRp and improved pharmacokinetic properties.

Structure-activity relationship of purine ribonucleosides for inhibition of hepatitis C virus RNA-dependent RNA polymerase.

As part of a continued effort to identify inhibitors of hepatitis C viral (HCV) replication, we report here the synthesis and evaluation of a series of nucleoside analogues and their corresponding triphosphates. Nucleosides were evaluated for their ability to inhibit HCV RNA replication in a cell-based, subgenomic replicon system, while nucleoside triphosphates were evaluated for their ability to inhibit in vitro RNA synthesis mediated by the HCV RNA-dependent RNA polymerase, NS5B. 2'-C-Methyladenosine and 2'-C-methylguanosine were identified as potent inhibitors of HCV RNA replication, and the corresponding triphosphates were found to be potent inhibitors of HCV NS5B-mediated RNA synthesis.

Imidazole acetic acid TAFIa inhibitors: SAR studies centered around the basic P(1)(') group.

Structural modifications of the aminopyridine P(1)(') group of imidazole acetic acid based TAFIa inhibitors led to the discovery of the aminocyclopentyl analog 28, a 1 nM TAFIa inhibitor with CLT(50) functional activity of 14 nM but without selectivity against CPB. While not as active, aminobutyl derivative 27 provided an improved 6.7-fold selectivity for TAFIa versus CPB.

Characterization of the inhibition of hepatitis C virus RNA replication by nonnucleosides.

The RNA-dependent RNA polymerase of hepatitis C virus (HCV) is necessary for the replication of viral RNA and thus represents an attractive target for drug development. Several structural classes of nonnucleoside inhibitors (NNIs) of HCV RNA polymerase have been described, including a promising series of benzothiadiazine compounds that efficiently block replication of HCV subgenomic replicons in tissue culture. In this work we report the selection of replicons resistant to inhibition by the benzothiadiazine class of NNIs.

Characterization of resistance to non-obligate chain-terminating ribonucleoside analogs that inhibit hepatitis C virus replication in vitro.

The urgent need for efficacious drugs to treat chronic hepatitis C virus (HCV) infection requires a concerted effort to develop inhibitors specific for virally encoded enzymes. We demonstrate that 2'-C-methyl ribonucleosides are efficient chain-terminating inhibitors of HCV genome replication. Characterization of drug-resistant HCV replicons defined a single S282T mutation within the active site of the viral polymerase that conferred loss of sensitivity to structurally related compounds in both replicon and isolated polymerase assays.

Electrochemiluminescence assay for basic carboxypeptidases: inhibition of basic carboxypeptidases and activation of thrombin-activatable fibrinolysis inhibitor.

Carboxypeptidases catalyze the removal of the C-terminal amino acid residues in peptides and proteins and exert important biological functions. Assays for carboxypeptidase activity that rely on change of absorbance generally suffer from low sensitivity and are difficult to adapt to high-throughput screening. We have developed a sensitive, robust assay for basic carboxypeptidase activity that makes use of electrochemiluminescent (ECL) detection of reaction product.

Inhibition of hepatitis C virus RNA replication by 2'-modified nucleoside analogs.

The RNA-dependent RNA polymerase (NS5B) of hepatitis C virus (HCV) is essential for the replication of viral RNA and thus constitutes a valid target for the chemotherapeutic intervention of HCV infection. In this report, we describe the identification of 2'-substituted nucleosides as inhibitors of HCV replication. The 5'-triphosphates of 2'-C-methyladenosine and 2'-O-methylcytidine are found to inhibit NS5B-catalyzed RNA synthesis in vitro, in a manner that is competitive with substrate nucleoside triphosphate.