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. Air liquid interface-cultured bronchial or small airway epithelium was infected with RSVA2. PC786 was applied apically or basolaterally once daily following peak virus load on Day 3 post inoculation. Apical wash was collected daily for determination of viral burden by PCR and plaque assay (primary endpoints) and biomarker analyses. The effects were compared with those of ALS-8112, an anti-RSV nucleoside analogue, and GS-5806, a fusion-protein inhibitor, which were treated basolaterally. Late intervention with GS-5806 did not show significant anti-viral effects, but PC786 produced potent, concentration-dependent inhibition of viral replication with viral load falling below detectable limits 3 days after treatment commenced in airway epithelium. These effects were superior to those of ALS-8112. PC786 showed inhibitory activities against RSV-induced increases of CCL5, IL-6, double-strand DNA and mucin. The effects of PC786 were also confirmed in small airway epithelium. Late therapeutic intervention with the RSV polymerase inhibitor, PC786, reduced the viral burden quickly in human airway epithelium. Thus, PC786 demonstrates the potential to be an effective therapeutic agent to treat active RSV infection.

Brookes DW ，Coates M ，Allen H ，Daly L ，Constant S ，Huang S ，Hows M ，Davis A ，Cass L ，Ayrton J ，Knowles I ，Strong P ，Rapeport G ，Ito K ... -  《-》

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

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.

Coates M ，Brookes D ，Kim YI ，Allen H ，Fordyce EAF ，Meals EA ，Colley T ，Ciana CL ，Parra GF ，Sherbukhin V ，Stockwell JA ，Thomas JC ，Hunt SF ，Anderson-Dring L ，Onions ST ，Cass L ，Murray PJ ，Ito K ，Strong P ，DeVincenzo JP ，Rapeport G ... -  《-》

Differential antiviral activities of respiratory syncytial virus (RSV) inhibitors in human airway epithelium.

Mirabelli C ，Jaspers M ，Boon M ，Jorissen M ，Koukni M ，Bardiot D ，Chaltin P ，Marchand A ，Neyts J ，Jochmans D ... -  《-》

Safety and Antiviral Effects of Nebulized PC786 in a Respiratory Syncytial Virus Challenge Study.

PC786 is a nebulized nonnucleoside respiratory syncytial virus (RSV) polymerase inhibitor designed to treat RSV, which replicates in the superficial layer of epithelial cells lining the airways. Fifty-six healthy volunteers inoculated with RSV-A (Memphis 37b) were randomly dosed with either nebulized PC786 (5 mg) or placebo, twice daily for 5 days, from either 12 hours after confirmation of RSV infection or 6 days after virus inoculation. Viral load (VL), disease severity, pharmacokinetics, and safety were assessed until discharge. RSV infection was confirmed by reverse-transcription quantitative polymerase chain reaction with any positive value (intention-to-treat infected [ITT-I] population) or RSV RNA ≥1 log10 plaque-forming unit equivalents (PFUe)/mL (specific intention-to-treat infection [ITT-IS] population) in nasal wash samples. In the ITT-I population, the mean VL area under the curve (AUC) was lower in the PC786 group than the placebo group (274.1 vs 406.6 log10 PFUe/mL × hour; P = .0359). PC786 showed a trend toward reduction of symptom score and mucous weight. In ITT-IS (post hoc analysis), the latter was statistically significant as well as VL AUC (P = .0126). PC786 showed an early time to maximum plasma concentration, limited systemic exposure, and long half-life and consequently a 2-fold accumulation over the 5-day dosing period. PC786 was well tolerated. Nebulized PC786 demonstrated a significant antiviral effect against RSV, warranting further clinical study. ClinicalTrials.gov: NCT03382431; EudraCT: 2017-002563-18.

DeVincenzo J ，Cass L ，Murray A ，Woodward K ，Meals E ，Coates M ，Daly L ，Wheeler V ，Mori J ，Brindley C ，Davis A ，McCurdy M ，Ito K ，Murray B ，Strong P ，Rapeport G ... -  《-》

Molecular Basis for the Selective Inhibition of Respiratory Syncytial Virus RNA Polymerase by 2'-Fluoro-4'-Chloromethyl-Cytidine Triphosphate.

Deval J ，Hong J ，Wang G ，Taylor J ，Smith LK ，Fung A ，Stevens SK ，Liu H ，Jin Z ，Dyatkina N ，Prhavc M ，Stoycheva AD ，Serebryany V ，Liu J ，Smith DB ，Tam Y ，Zhang Q ，Moore ML ，Fearns R ，Chanda SM ，Blatt LM ，Symons JA ，Beigelman L ... -  《-》