Discovery of New Inhibitors of Hepatitis C Virus NS3/4A Protease and Its D168A Mutant

Abstract

Hepatitis C virus (HCV) is a human pathogen with high morbidity. The HCV NS3/4A protease is essential for viral replication and is one of the top three drug targets. Several drugs targeting the protease have been developed, but drug-resistant mutant strains emerged. Here, we screened a library and synthesized a novel class of small molecules based on a tryptophan derivative scaffold identified as HCV NS3/4A protease inhibitors that are active against both wild type and mutant form of the protease. Only the compounds with predicted binding poses not affected by the most frequent mutations in the active site were selected for experimental validation. The antiviral activities were evaluated by replicon and enzymatic assays. Twenty-two compounds were found to inhibit HCV with EC50 values ranging between 0.64 and 63 μM with compound 22 being the most active. In protease assays, 22 had a comparable inhibition profile for the common mutant HCV GT1b D168A and the wild-type enzyme. However, in the same assay, the potency of the approved drug, simeprevir, decreased 5.7-fold for the mutant enzyme relative to the wild type. The top three inhibitors were also tested against four human serine proteases and were shown to be specific to the viral protease. The fluorescence-based cell viability assay demonstrated a sufficient therapeutic range for the top three candidates.

Potential of diterpene compounds as antivirals, a review

“…NS3/4A protease is an enzyme responsible for the selective cleavage of polyproteins into individual viral proteins. This protease plays an essential role in HCV replication, one of the three HCV drug targets ( Meewan et al, 2019 ).…”

Antiviral Agents against Flavivirus Protease: Prospect and Future Direction

“…Viral proteases in general are highly promising drug targets. Examples include ten HIV-1 protease inhibitors (PIs) [ 45 , 46 , 47 ] and two HCV PIs [ 48 , 49 , 50 ]. Thus, it is plausible that a protease inhibitor for flaviviruses will be efficacious in the clinic.…”

Antiviral Agents Against Flavivirus Protease: Prospect and Future Direction

“…The flavivirus NS2B-NS3 protease is one of the most promising validated targets for developing a pan flavivirus treatment which is evidenced by the clinical availability of ten HIV-1 protease inhibitors (PIs) [42][43][44] and the two HCV Protease inhibitors [45][46][47]. Thus, it is plausible that a protease inhibitor for flaviviruses will be efficacious in the clinic.…”