Novel potent inhibitors of hepatitis C virus (HCV) NS3 protease with cyclic sulfonyl P3 cappings

Unveiling sultam in drug discovery: spotlight on the underexplored scaffold

Decades ago, the application of cyclic sulfonamide (sultam) and its derivatives primarily focused on their antibacterial properties. However, recent years have seen a shift in research attention towards exploring their potential as anticancer, anti-inflammatory, antidiabetic, and antiviral agents. Despite this broadening scope, only a few sultam drugs have made it to the commercial market, as much of the research on sultams remains in the discovery phase. This class of compounds holds significant promise and remains pertinent in pharmaceutical research. Due to sultam's relevance and growing importance in drug discovery, this review paper aims to consolidate and examine the biological activities of sultam derivatives ranging from 4 to 8-membered ring structures.

Boceprevir: an oral protease inhibitor for the treatment of chronic HCV infection

Chronic hepatitis C (CHC) virus infection affects more than 170 million people globally. The aim of treatment of CHC is to affect sustained elimination of the virus (a sustained virological response [SVR]). The success and duration of therapy with interferon is dependent on HCV genotype. The current standard of care comprises combined treatment with pegylated interferon and ribavirin. Rates of SVR in patients with genotype 1 infection, the least responsive group, are less than 50%. Boceprevir is a ketoamide protease inhibitor that binds reversibly to the HCV nonstructural NS3 protease active site inhibiting intracellular viral replication. Phase III clinical studies have demonstrated that, in combination with the current standard of care, boceprevir significantly increases the SVR rate in both treatment-naive and previously treated patients with genotype 1 CHC. Both the US FDA and EMA have approved boceprevir for the treatment of genotype 1 CHC: the first directly-acting antiviral drug to be licensed for this indication. This article will review the pharmacology and pharmacodynamics of boceprevir, the efficacy and safety of the drug, and explore possible future developments in the management of CHC.

Inhibition of hepatitis C virus replication by herbal extract: Phyllanthus amarus as potent natural source

Hepatitis C virus infection is a major health problem worldwide. Developing effective antiviral therapy for HCV is the need of the hour. The viral enzymes NS3 protease and NS5B RNA dependent RNA polymerase are essential enzymes for polyprotein processing and viral RNA replication and thus can be potential targets for screening anti-HCV compounds. A large number of phytochemicals are present in plants, which are found to be promising antiviral agents. In this study, we have screened inhibitory effect of different plant extracts against the NS3 and NS5B enzymes of hepatitis C virus. Methanolic extracts were prepared from various plant materials and their inhibitory effects on the viral enzymes were determined by in vitro enzyme assays. Effect on viral RNA replication was investigated by using TaqMan Real time RT-PCR. Interestingly, Phyllanthus amarus root (PAR) extract showed significant inhibition of HCV-NS3 protease enzyme; whereas P. amarus leaf (PAL) extract showed considerable inhibition of NS5B in the in vitro assays. Further, the PAR and PAL extracts significantly inhibited replication of HCV monocistronic replicon RNA and HCV H77S viral RNA in HCV cell culture system. However, both PAR and PAL extracts did not show cytotoxicity in Huh7 cells in the MTT assay. Furthermore, addition of PAR together with IFN-α showed additive effect in the inhibition of HCV RNA replication. Results suggest the possible molecular basis of the inhibitory activity of PA extract against HCV which would help in optimization and subsequent development of specific antiviral agent using P. amarus as potent natural source.

HCV drug discovery aimed at viral eradication

Hepatitis C virus (HCV) causes significant morbidity and mortality worldwide with nearly 3% of the world population infected by this virus. Fortunately, this virus does not establish latency, and hence it may be possible to eradicate it. HCV is strongly associated with liver cirrhosis and hepatocellular carcinoma and is currently treated with pegylated interferon-alpha (peg-IFN-alpha) and ribavirin. Unfortunately, these limited treatment options often produce significant side effects, and currently, complete eradication of virus with combined drug modalities has not yet been achieved for the majority of chronically HCV-infected individuals. Restricted treatment options, lack of a universal cure for HCV and the link between chronic infection, liver cirrhosis and hepatocellular carcinoma necessitate design of novel drugs and treatment options. Understanding the relationship between the immune response, viral clearance and inhibition of viral replication with pharmacology-based design can ultimately allow for complete eradication of HCV. This review focuses upon significant novel preclinical and clinical specifically targeted antiviral therapy (STAT-C) drugs under development, highlights their mechanism of action, and discusses their impact on systemic viral loads and permanent clearance of infection.