Matthew Coates

Preclinical Characterization of PC786, an Inhaled Small-Molecule Respiratory Syncytial Virus L Protein Polymerase Inhibitor

ABSTRACT Although respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and young children, attempts to develop an effective therapy have so far proved unsuccessful. Here we report the preclinical profiles of PC786, a potent nonnucleoside RSV L protein polymerase inhibitor, designed for inhalation treatment of RSV infection. PC786 demonstrated a potent and selective antiviral activity against laboratory-adapted or clinical isolates of RSV-A (50% inhibitory concentration [IC50], <0.09 to 0.71 nM) and RSV-B (IC50, 1.3 to 50.6 nM), which were determined by inhibition of cytopathic effects in HEp-2 cells without causing detectable cytotoxicity. The underlying inhibition of virus replication was confirmed by PCR analysis. The effects of PC786 were largely unaffected by the multiplicity of infection (MOI) and were retained in the face of established RSV replication in a time-of-addition study. Persistent anti-RSV effects of PC786 were also demonstrated in human bronchial epithelial cells. In vivo intranasal once daily dosing with PC786 was able to reduce the virus load to undetectable levels in lung homogenates from RSV-infected mice and cotton rats. Treatment with escalating concentrations identified a dominant mutation in the L protein (Y1631H) in vitro. In addition, PC786 potently inhibited RSV RNA-dependent RNA polymerase (RdRp) activity in a cell-free enzyme assay and minigenome assay in HEp-2 cells (IC50, 2.1 and 0.5 nM, respectively). Thus, PC786 was shown to be a potent anti-RSV agent via inhibition of RdRp activity, making topical treatment with this compound a novel potential therapy for the treatment of human RSV infections.

Nasosorption as a Minimally Invasive Sampling Procedure: Mucosal Viral Load and Inflammation in Primary RSV Bronchiolitis

Summary We used nasosorption as a noninvasive method of respiratory mucosal sampling in a paediatric virology setting. Nasosorption was well tolerated and demonstrated respiratory syncytial virus load to be associated with disease severity and elevated mediators of inflammation.

Reduced Nasal Viral Load and IFN Responses in Infants with RSV Bronchiolitis and Respiratory Failure

Rationale: Respiratory syncytial virus (RSV) bronchiolitis is a major cause of morbidity and mortality in infancy. Severe disease is believed to result from uncontrolled viral replication, an excessive immune response, or both. Objectives: To determine RSV load and immune mediator levels in nasal mucosal lining fluid by serial sampling of nasal fluids from cases of moderate and severe bronchiolitis over the course of infection. Methods: Infants with viral bronchiolitis necessitating admission (n = 55) were recruited from a pediatric center during 2016 and 2017. Of these, 30 were RSV infected (18 “moderate” and 12 mechanically ventilated “severe”). Nasal fluids were sampled frequently over time using nasosorption devices and nasopharyngeal aspiration. Hierarchical clustering of time‐weighted averages was performed to investigate cytokine and chemokine levels, and gene expression profiling was conducted. Measurements and Main Results: Unexpectedly, cases with severe RSV bronchiolitis had lower nasal viral loads and reduced IFN‐&ggr; and C‐C chemokine ligand 5/RANTES (regulated upon activation, normal T cell expressed and secreted) levels than those with moderate disease, especially when allowance was made for disease duration (all P < 0.05). Reduced cytokine/chemokine levels in severe disease were also seen in children with other viral infections. Gene expression analysis of nasopharyngeal aspiration samples (n = 43) confirmed reduced type‐I IFN gene expression in severe bronchiolitis accompanied by enhanced expression of MUC5AC and IL17A. Conclusions: Infants with severe RSV bronchiolitis have lower nasal viral load, CXCL10 (C‐X‐C motif chemokine ligand 10)/IP‐10, and type‐I IFN levels than moderately ill children, but enhanced MUC5AC (mucin‐5AC) and IL17A gene expression in nasal cells.

Discovery of novel benzothienoazepine derivatives as potent inhibitors of respiratory syncytial virus

The development of novel non-nucleoside inhibitors of the RSV polymerase complex is of significant clinical interest. Compounds derived from the benzothienoazepine core, such as AZ-27, are potent inhibitors of RSV viruses of the A-subgroup, but are only moderately active against the B serotype and as yet have not demonstrated activity in vivo. Herein we report the discovery of several novel families of C-2 arylated benzothienoazepine derivatives that are highly potent RSV polymerase inhibitors and reveal an exemplary structure, compound 4a, which shows low nanomolar activity against both RSV A and B viral subtypes. Furthermore, this compound is effective at suppressing viral replication, when administered intranasally, in a rodent model of RSV infection. These results suggest that compounds belonging to this chemotypes have the potential to provide superior anti-RSV agents than those currently available for clinical use.

Late therapeutic intervention with a respiratory syncytial virus L‐protein polymerase inhibitor, PC786, on respiratory syncytial virus infection in human airway epithelium

Effective anti‐respiratory syncytial virus (RSV) agents are still not available for clinical use. Current major targets are virus surface proteins, such as a fusion protein involved in viral entry, but agents effective after RSV infection is established are required. Here we have investigated the effects of late therapeutic intervention with a novel inhaled RSV polymerase inhibitor, PC786, on RSV infection in human airway epithelium.