Targeting the RSV N0/P complex with constrained alpha-helical peptides

Each year, the infection of infants with RSV is the cause of a large number of hospitalizations and deaths worldwide. The current standard of care, Synagis, is used as a preventive medicine for premature children only, and there is no drug available to treat the patients who are suffering from this infection. Targeting the polymerase replication complex is a strategy that has been used successfully to develop drugs against other viruses such as HIV, HCV and HBV. In this project, we wish to inhibit the replication complex by disrupting the N0/P interaction. N0 is the nucleoprotein species that is bound as a complex to the phosphoprotein prior to nucleic acid encapsidation. Recently, the N-terminal region (1-29) of the RSV P protein has been identified as sufficient to bind to N0, and the importance of each P residues has been assessed through alanine scanning mutagenesis experiments. Additionally, NMR studies have provided evidence that P (13-25) has a propensity to fold into an alpha helix in solution. We used these data to design stabilized alpha-helical peptides, with the aim to screen for dominant negative inhibitors of the RSV N0/P interaction. The peptides were stabilized as macrocyclic peptides using the stapled peptide technology, because this technique can improve their potency, proteolytic stability and cellular permeability. The putative P alpha-helix was plotted onto an alpha-helical wheel, and the amino-acids located on the non-interacting site of the helix were selected for modification with the non-natural amino-acids required for stapling. We will present the results of this stapled peptide scan by reporting i) the conformational analysis by circular dichroism, ii) the biological activity in a novel N0-P fluorescence polarization assay, a viral replication assay and a cytotoxicity assay and iii) the in vivo proof of concept by intranasal administration of a hit peptide, HEVS 124, to BALB/c mice inoculated with a Luc-encoding RSV.