Design and synthesis of antivirals benzimidazoles and quinoxalines
Authors: Abdelhafez Tawfeek H. , Khattab Muhammad K.F. , Temirak Ahmed , Shaker Yasser M. , Abu Bakr Sherifa M. , Abbas Eman M. , Khairat Sarah M.H. , Abdullaziz Mona A. , El Rashidi Ahmed A. , Mohamed-Ezzat Reham A. , Galal Shadia A. , Moustafa Passant E.I. , El Awdan Sally A. , Ali Hamed I. , El-Eraky Wafaa I. , El Awady Mostafa K. , El Diwani Hoda I. 
Published: July 2022

Background
Chronic hepatitis C can cause serious, even deadly, health problems like cirrhosis and liver cancer. There is no vaccine for hepatitis C. The hepatitis C virus (HCV) NS5B gene encodes RNA-dependent RNA polymerase, which is a key player in viral replication and is a promising target for the development of antiviral drugs. Drugs having benzimidazole and quinoxaline scaffolds were described to selectively block the activity of NS5B polymerase. New antiviral drugs have to be developed to overcome drug resistance.

Objective
The main goal of this work was to develop new effective anti-bovine viral diarrhea virus (BVDV) and anti-HCV agents by designing and synthesizing benzimidazole and quinoxaline derivatives.

Materials and methods
Synthesis of target compounds based on benzimidazole and quinoxaline scaffolds according to reported methods was done. Antiviral activity against BVDV was studied. BVDV and Madin-Darby bovine kidney cells were obtained from the American Type Culture Collection. Antiviral activity against HCV infectious system was evaluated. Huh7.5.1 cells were cultured and treated with different concentrations of studied compounds. GOLD molecular docking study was evaluated. The crystal structures of the HCV polymerases in complex with its co-crystalized native ligand were retrieved from the Protein Data Bank. Acute toxicity studies were carried out on animals. Results and conclusion A rational design based on the previous work was performed to indicate new promising benzimidazole and quinoxaline derivatives to be synthesized and tested as anti-HCV compounds. New benzimidazole and quinoxaline derivatives were synthesized and tested for anti-BVDV activity. All of the compounds showed strong activity against BVDV, except 17, which exhibited moderate antiviral activity. Compounds 12 and 13 were the most promising. The anti-HCV activity of 12 and 13 was investigated after infection of Huh 7.5.1 cells with HCV (JFH1). The IC50 values of 12 and 13 were found to be 19.1 and 49.4 μM, respectively; their CC50 values were 752.25 and 1480 μM, respectively; and their SI were calculated to be 39.3 for 12 and 30.03 for 13. The assigned compounds were docked into the hepatitis-C virus polymerase enzyme (pdb: 3FRZ) using GOLD 5.2.2 docking program. They revealed GoldScore fitness activities of 69.78–80.71, which is comparable to the native ‘PF-00868554’ ligand as a potent HCV polymerase inhibitor. They are bound by up to three hydrogen bonds, mainly with aminoacids R422 and S476, as well as they were embedded into the two small hydrophobic pockets formed by amino acid residues including L419, M423, L482, and L497. The acute toxicity of compound 12 on rats was tested. No signs of toxicity, no deaths, and no significant changes were observed in the biochemical parameters of liver and kidneys.