In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS3/4A Protease Inhibitor Glecaprevir

Abstract

Glecaprevir (formerly ABT-493) is a novel hepatitis C virus (HCV) NS3/4A protease inhibitor (PI) with pangenotypic activity. It inhibited the enzymatic activity of purified NS3/4A proteases from HCV genotypes 1 to 6 in vitro (half-maximal [50%] inhibitory concentration = 3.5 to 11.3 nM) and the replication of stable HCV subgenomic replicons containing proteases from genotypes 1 to 6 (50% effective concentration [EC₅₀] = 0.21 to 4.6 nM). Glecaprevir had a median EC₅₀ of 0.30 nM (range, 0.05 to 3.8 nM) for HCV replicons containing proteases from 40 samples from patients infected with HCV genotypes 1 to 5. Importantly, glecaprevir was active against the protease from genotype 3, the most-difficult-to-treat HCV genotype, in both enzymatic and replicon assays demonstrating comparable activity against the other HCV genotypes. In drug-resistant colony selection studies, glecaprevir generally selected substitutions at NS3 amino acid position A156 in replicons containing proteases from genotypes 1a, 1b, 2a, 2b, 3a, and 4a and substitutions at position D/Q168 in replicons containing proteases from genotypes 3a, 5a, and 6a. Although the substitutions A156T and A156V in NS3 of genotype 1 reduced susceptibility to glecaprevir, replicons with these substitutions demonstrated a low replication efficiency in vitro Glecaprevir is active against HCV with most of the common NS3 amino acid substitutions that are associated with reduced susceptibility to other currently approved HCV PIs, including those at positions 155 and 168. Combination of glecaprevir with HCV inhibitors with other mechanisms of action resulted in additive or synergistic antiviral activity. In summary, glecaprevir is a next-generation HCV PI with potent pangenotypic activity and a high barrier to the development of resistance.

Keywords: ABT-493; HCV; NS3/4A protease inhibitor; antiviral activity; glecaprevir; resistance.

FIG 1

Chemical structure of glecaprevir.

FIG 2

Inhibition of drug-resistant colony selection with the combination of glecaprevir and pibrentasvir in HCV genotype 1 replicon cells. Genotype 1a and 1b replicon cells seeded on 150-mm cell culture plates were treated for approximately 3 weeks with either glecaprevir or pibrentasvir individually or in combination at 10-fold the respective EC₅₀ for each replicon cell line. All treatments also contained 400 μg/ml G418. Drug-resistant colonies that survived the treatment were fixed and stained with crystal violet, and the number of colonies was determined.