48.    NeAntivirals for bovine viral diarrhea virus: evaluation of compounds selected by                virtual screening against viral RNA polymerase

Bovine viral diarrhea virus (BVDV) is a pestivirus whose infection in cattle is distributed worldwide. The disease caused by BVDV can manifest as generalised immunosuppression, with evidence of synergistic effects with other pathogens, fertility problems in male and female cattle, and other often more variable signs such as decreased milk production and weight gain, fever, diarrhoea and respiratory dysfunction. Thus, BVDV causes substantial economic losses. There is no specific treatment for BVDV infections and the use of antivirals could complement
vaccination as a tool of control and reduce economic losses. Viral RNA-dependent RNA polymerase (RdRp) is essential for viral genome replication and constitutes an attractive target for the discovery of antivirals. To obtain selective inhibitors of BVDV, more than 1000 compounds from HitFinder commercial databases and 230 compounds from the laboratory of Medicinal Chemistry (CIBION-CONICET) were virtually screened. A visual analysis of the ligand-receptor binding and the prediction of pharmacological properties were done. This led to the selection of several structurally different candidates that were either synthesized (S1-S5) or purchased (S6-S13). Here, we report the in vitro antiviral screening of thirteen selected molecules that were synthesized (S1-S5) or purchased (S6-S13). The cytotoxicity in MDBK cells was assessed by MTS/PMS and the anti-BVDV (NADL) activity was evaluated by cytopathic effect reduction. At least three compounds resulted active: S1, S7 and S9 with EC50 values of 9.68±0.49 μM (SI: 5.77); 0.98±0.01 μM (SI: 11.53); and 6.40±0.70 μM (SI: 12.90), respectively. Additionally, to improve the antiviral potency of quinazoline S1, whose synthesis is simple and easily scalable, eleven derivatives were synthesized and evaluated. As result, four of them showed improved antiviral activity, with EC50 ranging from 0.9 to 2.8 μM. In conclusion, new molecules with potent in vitro anti-BVDV activity were discovered. These studies highlight the potential of virtual screening for the efficient identification of new antivirals leads.