Broad spectrum inhibitors of paramyxovirus envelope proteins

Abstract Human parainfluenza viruses (HPIV) cause a significant portion of childhood croup, bronchiolitis and pneumonia in the U.S. and worldwide, yet no effective drugs or vaccines are available. For the lethal Nipah (NiV) and Hendra (HeV) viruses, in the face of human-to-human transmission of NiV, there is risk for global spread as well as accidental or deliberate exposure. Despite the existence of antibody preparations for passive immunoprophylaxis, there is no feasible approach to prevent or treat the human disease. These viruses serve as prototypes for emerging paramyxoviruses. With this application we build on recent breakthroughs that have led to a new broad-spectrum antiviral strategy based on inhibiting fusion during viral entry. We combine structure-based optimization of fusion inhibitory lipopeptides, backbone modification via partial replacement of α-amino acid residues with unnatural β-amino acid residues to enhance half-life, and addition of lipid components to enhance antiviral efficacy. Using virologic, ex vivo, and in vivo experiments we will develop powerful novel HPIV3/NiV/HeV fusion inhibitors that can be administered by inhalation. Validation of our strategies with circulating respiratory viruses and clinical NiV virus strains in vitro and in vivo will lead us to antiviral agents that are effective and practical in the clinical setting. Aim 1. Targeting the paramyxovirus fusion complex: Evaluate entry inhibitor approaches in vitro. We will develop fusion-inhibitory lipopeptides, combining conventional peptide design with backbone- modification and membrane targeting to optimize broad fusion inhibition activity for NiV, HeV, HPIV, and optimize potency, protease resistance, and tissue targeting of lead lipopeptides. We will evaluate antiviral activity and potential for antiviral resistance in authentic ex vivo models. Human airway and brain models will be employed to elicit resistant viruses in ex vivo evolution experiments, to study the molecular bases for antiviral activity and potential for resistance to lead peptides. Aim 2. Pharmacokinetics, biodistribution and efficacy of formulated lead antivirals in vivo. We will assess the biodistribution and immunogenicity, acute toxicity, and PK/PD via nasal or inhalation delivery of lead candidate series in small animal models, and evaluate efficacy of lead peptides for NiV/HeV in golden hamsters and for HPIV in cotton rats. An efficacy study for the NiV lead will be conducted in African green monkeys. We propose that peptide backbone modification and membrane targeting strategies will generate broad anti- paramyxovirus agents that can be delivered via inhalation with unprecedented efficacy and pharmacokinetic properties.