Studies on the mechanism of action of antiviral agents targeting the replication complex of hepatitis c virus

At the moment, several companies are studying the clinical potential of different all-oral combinations of direct-acting antivirals in ongoing studies. The most promising interferon-free combination therapies that are on the horizon include linear or cyclic NS3/4A protease inhibitors, nucleoside as well as non-nucleoside NS5B polymerase inhibitors , and NS5A inhibitors. DAAs that target NS3/4A (protease) and NS5B (RNA-dependent RNA polymerase) inhibit the enzymatic activity of these proteins. NS5A replication complex inhibitors will likely form a component of future interferon-free drug regimens but despite their remarkable potential to treat chronic hepatitis C, the detailed mechanism of action for this class of drug remains unclear. The goal of my work was to investigate the mechanism of action of different classes of antiviral agents believed to target the NS5A protein in the replication complex in order to improve the possibility to translate basic knowledge to a more meaningful clinical application. More specifically I focused my research on two classes of compounds, characterized by distinct resistance patterns in NS5A: a first class – with examples at the final stages of clinical development, represented by Daclatasvir (Lemm et al., 2011), and a second class - at earlier stages of development - represented by anilino-quinazolines such as A-831/AZD-2836 (Quinkert et al., 2008). I contributed to demonstrate that both of these inhibitor classes, by binding respectively to either HCV NS5A or to an NS5A-associated protein, PI4KIIIα, eventually interfere with the accumulation of PI4P 98 and cholesterol in the HCV replication membranous compartment, thus abrogating the ability of the virus form to replicate its RNA genome.