The Fight against the Influenza A Virus H1N1: Synthesis, Molecular Modeling, and Biological Evaluation of Benzofurazan Derivatives as Viral RNA Polymerase Inhibitors

Abstract

The influenza RNA polymerase complex, which consists of the three subunits PA, PB1, and PB2, is a promising target for the development of new antiviral drugs. A large library of benzofurazan compounds was synthesized and assayed against influenza virus A/WSN/33 (H1N1). Most of the new derivatives were found to act by inhibiting the viral RNA polymerase complex through disruption of the complex formed between subunits PA and PB1. Docking studies were also performed to elucidate the binding mode of benzofurazans within the PB1 binding site in PA and to identify amino acids involved in their mechanism of action. The predicted binding pose is fully consistent with the biological data and lays the foundation for the rational development of more effective PA-PB1 inhibitors.

A Broad Anti-influenza Hybrid Small Molecule That Potently Disrupts the Interaction of Polymerase Acidic Protein–Basic Protein 1 (PA-PB1) Subunits

“…While no small molecule targeting PB1-PB2 interaction is known, with only a few short peptides reported for this activity, 16,17 various small molecules able to disrupt the interactions between the PA and PB1 subunits have emerged during the last three years. [18][19][20][21][22][23][24][25] Their PPI inhibitory activity correlated to the inhibition of viral RdRP activity and of virus replication in cellular context, thus validating this antiviral strategy. Different approaches led to identify the PA-PB1 small molecule inhibitors reported so far ( Figure 1).…”

Learning from structure-based drug design and new antivirals targeting the ribonucleoprotein complex for the treatment of influenza

“…Nevertheless, quite potent inhibitors of PB2 cap-binding were recently developed with few reported interactions with cellular partners [70,71]. The endonuclease domain represents a specific target with an excellent druggable site [73][74][75][76][77][78]83,84]. Moreover, the PA--PB1 interaction represents an attractive target for inhibitors since the association of PA and PB1 subunits is essential for replication [85][86][87][88], and the sequence of these domains is highly conserved [89,90].…”

“…Therefore, interfering with the assembly of the RdRp complex could be a way to fight against influenza infection. A large library of drugs, in particular benzofurazan derivatives, was found to act by inhibiting the viral RdRp complex through disruption of the complex formed by PA and PB1 subunits [81][82][83][84]. Since the association of these subunits is essential for replication [85][86][87][88] and the sequence of this domain is highly conserved [89,90] this interaction represents an attractive target for inhibitors.…”

“…Due to the crystallographic structures of the PA--peptide PB1 complex [63,64] a short peptide derived from the C terminus of PB1 has been shown to disrupt the interaction between the C-terminal part of PB1 and the N-terminal part of PB2 and to inhibit viral polymerase activity and replication [91]. Docking studies were performed to explore the structural features responsible for the biological activity of benzofurazan derivatives (Table 2) [83,84]. Docking suggested that their most reliable binding mode involves a :--stacking interactions with PA Trp706 of the benzofurazan scaffold, a hydrogen bond with Gln408 and electrostatic interactions with PA Lys643.…”

Structural analysis of H1N1 and H7N9 influenza A virus PA in the absence of PB1

“…Viral polymerases have been successful therapeutic targets for other single-stranded RNA viruses such as HIV and Hepatits C. In addition to inhibitors of the PA N enzyme111216, there have been reports of peptide inhibitors1718 and small molecule inhibitors192021 that bind to PA and disrupt the PA-PB1 interaction. Computational docking and other structure-based drug design strategies could exploit the bound state of PA-CTD with PB1-peptide removed1314.…”