Benzimidazole analogs inhibit respiratory syncytial virus G protein function

Antiviral Res. 2015 Sep;121:31-8. doi: 10.1016/j.antiviral.2015.06.016. Epub 2015 Jun 24.

Abstract

Human respiratory syncytial virus (hRSV) is a highly contagious Paramyxovirus that infects most children by age two, generating an estimated 75,000-125,000 hospitalizations in the U.S. annually. hRSV is the most common cause of bronchiolitis and pneumonia among infants and children under 1year of age, with significant mortality among high-risk groups. A regulatory agency-approved vaccine is not available, and existing prophylaxis and therapies are limited to use in high-risk pediatric patients; thus additional therapies are sorely needed. Here, we identify a series of benzimidazole analogs that inhibit hRSV infection in vitro with high potency, using a previously-reported high-throughput screening assay. The lead compound, SRI 29365 (1-[6-(2-furyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl]methyl-1H-benzimidazole), has an EC50 of 66μM and a selectivity >50. We identified additional compounds with varying potencies by testing commercially-available chemical analogs. Time-of-addition experiments indicated that SRI 29365 effectively inhibits viral replication only if present during the early stages of viral infection. We isolated a virus with resistance to SRI 29365 and identified mutations in the transmembrane domain of the viral G protein genomic sequence that suggested that the compound inhibits G-protein mediated attachment of hRSV to cells. Additional experiments with multiple cell types indicated that SRI 29365 antiviral activity correlates with the binding of cell surface heparin by full-length G protein. Lastly, SRI 29365 did not reduce hRSV titers or morbidity/mortality in efficacy studies using a cotton rat model. Although SRI 29365 and analogs inhibit hRSV replication in vitro, this work suggests that the G-protein may not be a valid drug target in vivo.

Keywords: Antiviral; G protein; Heparin; SAR; hRSV.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antiviral Agents / pharmacology*
  • Benzimidazoles / pharmacology*
  • Cell Line
  • Disease Models, Animal
  • Drug Resistance, Viral
  • High-Throughput Screening Assays
  • Humans
  • Microbial Sensitivity Tests
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism
  • Mutation
  • Respiratory Syncytial Virus Infections / pathology
  • Respiratory Syncytial Virus Infections / virology
  • Respiratory Syncytial Virus, Human / drug effects*
  • Respiratory Syncytial Virus, Human / physiology*
  • Sigmodontinae
  • Survival Analysis
  • Viral Envelope Proteins / antagonists & inhibitors*
  • Viral Envelope Proteins / genetics
  • Virus Attachment / drug effects*

Substances

  • Antiviral Agents
  • Benzimidazoles
  • Mutant Proteins
  • Viral Envelope Proteins
  • attachment protein G
  • benzimidazole