Design and Optimization of Quinazoline Derivatives: New Non-nucleoside Inhibitors of Bovine Viral Diarrhea Virus.

Bovine viral diarrhea virus (BVDV) belongs to the Pestivirus genus (Flaviviridae). In spite of the availability of vaccines, the virus is still causing substantial financial losses to the livestock industry. In this context, the use of antiviral agents could be an alternative strategy to control and reduce viral infections. The viral RNA-dependent RNA polymerase (RdRp) is essential for the replication of the viral genome and constitutes an attractive target for the identification of antiviral compounds. In a previous work, we have identified potential molecules that dock into an allosteric binding pocket of BVDV RdRp via a structure-based virtual screening approach. One of them, N-(2-morpholinoethyl)-2-phenylquinazolin-4-amine [1, 50% effective concentration (EC50) = 9.7 ± 0.5 µM], was selected to perform different chemical modifications. Among 24 derivatives synthesized, eight of them showed considerable antiviral activity. Molecular modeling of the most active compounds showed that they bind to a pocket located in the fingers and thumb domains in BVDV RdRp, which is different from that identified for other non-nucleoside inhibitors (NNIs) such as thiosemicarbazone (TSC). We selected compound 2-[4-(2-phenylquinazolin-4-yl)piperazin-1-yl]ethanol (1.9; EC50 = 1.7 ± 0.4 µM) for further analysis. Compound 1.9 was found to inhibit the in vitro replication of TSC-resistant BVDV variants, which carry the N264D mutation in the RdRp. In addition, 1.9 presented adequate solubility in different media and a high-stability profile in murine and bovine plasma.

Identification of potent bovine viral diarrhea virus inhibitors by a structure-based virtual screening approach.

Bovine viral diarrhea virus (BVDV) is a pestivirus whose infection in cattle is globally distributed. The use of antivirals could complement vaccination as a tool of control and reduce economic losses. The RNA-dependent RNA polymerase (RdRp) of the virus is essential for its genome replication and constitutes an attractive target for the identification of antivirals. With the aim of obtaining selective BVDV inhibitors, the crystal structure of BVDV RdRp was used to perform a virtual screening. Approximately 15,000 small molecules from commercial and in-house databases were evaluated and several structurally different compounds were tested in vitro for antiviral activity. Interestingly, of twelve evaluated compounds, five were active and displayed EC50 values in the sub and low-micromolar range. Time of drug addition experiment and measured intracellular BVDV RNA showed that compound 7 act during RNA synthesis. Molecular Dynamics and MM/PBSA calculation were done to characterize the interaction of the most active compounds with RdRp, which will allow future ligand optimization. These studies highlight the use of in silico screening to identify a new class of BVDV inhibitors.

Synthesis, antiviral evaluation and molecular docking studies of N4-aryl substituted/unsubstituted thiosemicarbazones derived from 1-indanones as potent anti-bovine viral diarrhea virus agents.

A series of N4-arylsubstituted thiosemicarbazones derived from 1-indanones and a set of compounds lacking such substitution in the N4 position of the thiosemicarbazone moiety were synthesized and evaluated for their anti-bovine viral diarrhea virus (BVDV) activity. Among these, derivatives 2 and 15 displayed high activity (EC50=2.7±0.4 and 0.7±0.1µM, respectively) as inhibitors of BVDV replication. Novel key structural features related to the anti-BVDV activity were identified by structure-activity relationship (SAR) analysis. In a previous study, the thiosemicarbazone of 5,6-dimethoxy-1-indanone (5,6-TSC) was characterized as a non-nucleoside inhibitor (NNI) of the BVDV RNA-dependent RNA polymerase. In the present work, cross-resistance assays were performed with the most active compounds. Such studies were carried out on 5,6-TSC resistant BVDV (BVDV-TSCr T1) carrying mutations in the viral polymerase. This BVDV mutant was also resistant to compound 15. Molecular docking studies and MM/PBSA calculations were performed to assess the most active derivatives at the 5,6-TSC viral polymerase binding site. The differences in the interaction pattern and the binding affinity of derivative 15 either to the wild type or BVDV-TSCr T1 polymerase were key factors to define the mode of action of this compound.