Giuseppe Manfroni
Università degli Studi di Perugia, Italy
Title: Inhibition of the RNA-dependent RNA polymerasic activity of Flavivirus NS5 by heterocyclic compounds
Biography
Biography: Giuseppe Manfroni
Abstract
Among more than 70 related members of Flavivirus genus, Dengue virus (DENV), West Nile virus (WNV), Japanese encephalitis virus (JEV), Yellow fever virus (YFV), and Zika virus (ZV) are considered (re)-emerging pathogens that were originally endemic in the tropical regions but recently are spreading also in a wider geographic area. Indeed, there are several environmental, demographic, and ecological factors that promote the worldwide diffusion of known and/or novel flaviviruses. Flaviviruses can produce from mild flu-like symptoms to hemorrhagic fevers, hepatitis and neuropathies, such as encephalopathy, meningitis, and microcephaly in human embryos depending on the infective agents. Vaccines are available against YFV, JEV, TBEV, and more recently against DENV but the coverage is far from being complete. Moreover, the lack of an effective and specific therapy further worsens the scenario. The RNA-dependent RNA polymerase (RdRp) of the non-structural NS5 protein is one of the most favored target to find new potential anti- Flavivirus drugs. With the aim to find new inhibitors of the RdRp we undertook a research program exploiting, consecutively, two different approaches: i) A virtual screening carried out on the NS5 polymerase domain (DENV RdRp, 2j7U) followed by a biochemical validation on the isolate target, ii) a direct biochemical screening carried out on DENV NS5 polymerase with the intent to not exclude any potential hit compounds eventually missed during the in silico procedures. Both these approaches were realized using an in-house library of about 200, published and unpublished, compounds previously designed and synthesized as HCV NS5B inhibitors. To validate the potential of the identified hits an anti-viral activity against a panel of Flavivirus was evaluated. The two strategies led us to identify new RdRp inhibitors able to reduce the polymerase activity in the low micromolar range. In particular, the in silico procedure (i) was fruitful for the identification of a pyridobenzothiazole which was extensively characterized with biochemical and structural studies; the second approach (ii) led us to identify functionalized 2,1-benzothiaziens with promising anti-RdRp activity, not emerged as hit compounds during the in silico studies (Figure 1). Also in this case, a representative compound derived from a chemical optimization was better characterized in biochemical and virological assays. The strategy applied in this study led us to identify new promising inhibitors of the NS5 polymerase, worthy of further optimization with the final aim to discover anti-Flavivirus agents.