Understanding of the drug resistance mechanism of hepatitis C virus NS3/4A to paritaprevir due to D168N/Y mutations: A molecular dynamics simulation perspective.

Hepatitis C virus (HCV) NS3/4A protease is an attractive target for the development of antiviral therapy. However, the evolution of antiviral drug resistance is a major problem for treatment of HCV infected patients. Understanding of drug-resistance mechanisms at molecular level is therefore very important for the guidance of further design of antiviral drugs with high efficiency and specificity. Paritaprevir is a potent inhibitor against HCV NS3/4A protease genotype 1a. Unfortunately, this compound is highly susceptible to the substitution at D168 in the protease. In this work, molecular dynamics simulations of paritaprevir complexed with wild-type (WT) and two mutated strains (D168 N and D168Y) were carried out. Due to such mutations, the inhibitor-protein hydrogen bonding between them was weakened and the salt-bridge network among residues R123, R155 and D168 responsible for inhibitor binding was disrupted. Moreover, the per-residue free energy decomposition suggested that the main contributions from key residues such as Q80, V132, K136, G137 and R155 were lost in the D168 N/Y mutations. These lead to a lower binding affinity of paritaprevir for D168 N/Y variants of the HCV NS3/4A protease, consistent with the experimental data. This detailed information could be useful for further design of high potency anti-HCV NS3/4A inhibitors.