Resistance to Direct Antiviral Agents in Patients With Hepatitis C Virus Infection

Antiviral activities (mean or median maximum decrease in HCV RNA log10 IU/mL) of DAA agents, as determined from phase 1 monotherapy studies (3–14 days) in patients infected with HCV genotype 1. Different reagents or durations of treatment were not compared directly in these studies. In patients who received the DAA for 7–14 days, the decrease in viral load might not reflect only the activity of the DAA agent but also the emergence of resistant variants. *Clinical development stopped. (A) NS3 protease inhibitors. (B) Nucleoside inhibitors of NS5B. (C) Nonnucleoside inhibitors of NS5B. (D) NS5A inhibitor, indirect inhibitors and agents with unknown mechanism of action. QD, every day, BID, twice a day, TID, three times a day, BW, body weight, #, 900 mg BID stopped from further development due to increase of liver enzymes in single cases.

Molecular basis for different probabilities for selection of R155K/T/Q mutations in subtype 1a– vs subtype 1b–infected patients treated with a NS3 protease inhibitor. Selection of R155K/T requires 1 nucleotide exchange in subtype 1a but 2 nucleotide exchanges in subtype 1b patients. Selection of R155Q requires 1 nucleotide exchange in subtype 1b but 2 nucleotide exchanges in subtype 1a patients.

Amino acid positions within the NS3/4A protease associated with (A) resistance mutations to different NS3 protease inhibitors and a (B) cross-resistance table of different NS3 protease inhibitors based on mutations selected in patients from clinical studies and/or from in vitro studies. Amino acids forming the catalytic triad (H57, D81, S139) are highlighted. *Mutations associated with resistance in vitro but were not described in patients. **Mutations associated with resistance in vitro. Resistance mutations of linear NS3 protease inhibitors are shown in blue and resistance mutations described for macrocyclic NS3 protease inhibitors are shown in green.

Amino acid positions within the NS5B polymerase associated with (A) resistance mutations to different nucleoside and nonnucleoside inhibitors and a (B) cross-resistance table of different NS5B polymerase inhibitors based on mutations selected in patients or in vitro. Amino acids forming the catalytic triad (D318, D319, D220) are highlighted. *Mutations associated with resistance in patients. **Mutations associated with resistance in vitro. Mutations of 2′-C-methylcitidine and 4′-azidocytidine nucleoside inhibitors are shown in red and pink, respectively. For NNI-site 1, 2, 3, and 4 inhibitors resistance mutations are shown in orange, dark blue, dark green, and yellow, respectively.