Preclinical Characterization of the Novel Hepatitis C Virus NS3 Protease Inhibitor GS-9451

Abstract

GS-9451 is a selective hepatitis C virus (HCV) NS3 protease inhibitor in development for the treatment of genotype 1 (GT1) HCV infection. Key preclinical properties of GS-9451, including in vitro antiviral activity, selectivity, cross-resistance, and combination activity, as well as pharmacokinetic properties, were determined. In multiple GT1a and GT1b replicon cell lines, GS-9451 had mean 50% effective concentrations (EC 50 s) of 13 and 5.4 nM, respectively, with minimal cytotoxicity; similar potency was observed in chimeric replicons encoding the NS3 protease gene of GT1 clinical isolates. GS-9451 was less active in GT2a replicon cells (EC 50 ‫؍‬ 316 nM). Additive to synergistic in vitro antiviral activity was observed when GS-9451 was combined with other agents, including alpha interferon, ribavirin, and the polymerase inhibitors GS-6620 and tegobuvir (GS-9190), as well as the NS5A inhibitor ledipasvir (GS-5885). GS-9451 retained wild-type activity against multiple classes of NS5B and NS5A inhibitor resistance mutations. GS-9451 was stable in hepatic microsomes and hepatocytes from human and three other tested species. Systemic clearance was low in dogs and monkeys but high in rats. GS-9451 showed good oral bioavailability in all three species tested. In rats, GS-9451 levels were ϳ40-fold higher in liver than plasma after intravenous dosing, and elimination of GS-9451 was primarily through biliary excretion. Together, these results are consistent with the antiviral activity observed in a recent phase 1b study. The results of in vitro cross-resistance and combination antiviral assays support the ongoing development of GS-9451 in combination with other agents for the treatment of chronic HCV infection.T he NS3 serine protease of hepatitis C virus (HCV), which liberates essential nonstructural proteins from the HCV polyprotein, is required for viral replication (1) and may promote infection by blunting host innate immunity (2). Inhibitors of the HCV NS3/4A serine protease can induce rapid and substantial reductions in viral load. The NS3 protease inhibitors telaprevir (Incivek) and boceprevir (Victrelis) are separately indicated for use in triple therapy combinations with pegylated alpha interferon (PEG-IFN) and ribavirin (RBV) for treating chronic genotype 1 (GT1) HCV infection. When added to PEG-IFN and RBV, telaprevir and boceprevir independently have increased rates of sustained virologic response (SVR) in GT1 HCV-infected patients (3-13). However, the standard of care still has many limitations, including a complex treatment regimen, significant drug-drug interaction potential, and adverse effects that can limit tolerability.There is continued need for novel NS3 protease inhibitors that are well tolerated, have minimal potential for drug-drug interactions, and provide more favorable treatment regimens to improve compliance. GS-9451 is a novel acyclic HCV protease inhibitor being developed for the treatment of GT1 HCV infection. GS-9451 inhibits NS3 protease by binding the active site of the enzyme in a reve...

New Hepatitis C Therapies: The Toolbox, Strategies, and Challenges

“…They are given every 8 hours (telaprevir can be given every 12 hours). A number of second-wave, first-generation NS3-4A protease inhibitors have reached phase II or III clinical development, including simeprevir (Janssen), 12 approved in November 2013 in the United States and in May 2014 in the European Union, faldaprevir (Boehringer-Ingelheim, Ingelheim, Germany), 13,14 asunaprevir (Bristol-Myers Squibb, Princeton, NJ), 15 ABT-450 (Abbvie, North Chicago, IL), danoprevir (Roche, Basel, Switzerland), 16 sovaprevir (Achillion, New Haven, CT), vaniprevir (Merck), 17 vedroprevir (Gilead, Foster City, CA), 18,19 and IDX320 (Idenix, Cambridge, MA) ( Table 1). These drugs are dosed once or twice per day.…”

Synthesis of Cyclic and Acyclic Nucleoside Phosphonates and Sulfonamides Derived from 6‐(Thiophen‐2‐yl)‐7‐fluoro‐7‐deazapurine

“…All the title compounds were submitted for screening of biological activities. They were tested for cytotoxic activity on a panel of leukemia (CCRF‐CEM, CEM‐DNR, K562, and K562‐TAX) and cancer cell lines (A549, HCT116 and HCT116p53‐/), for antiviral activity (hepatitis C virus, dengue, HIV, respiratory syncytial virus, influenza, coxsackie and herpes viruses) and for antibacterial activity ( Staphylococcus aureus 4591, Enterococcus faecium 419/ANA, Enterococcus faecalis CCM 4224, Escherichia coli CE5556, Pseudomonas aeruginosa R, Candida albicans CCM 8161 and Staphylococcus aureus CCM 3953 ) . However, all the final compounds were found inactive (IC 50 > 50 µ m ) in these assays, suggesting that the ribose moiety is crucial for cytotoxic activity of this class of nucleosides and that installing of a stable phosphate surrogate does not increase the activity.…”

Nucleotide Prodrug Containing a Nonproteinogenic Amino Acid To Improve Oral Delivery of a Hepatitis C Virus Treatment

“…The EC 50 s, defined as the concentration at which there was a measured 50% decrease in HCV replicon level, were determined in replicon assay as previously described ( 24 ). Briefly, replicon cells were seeded into 96-well plates.…”