title: Benzimidazole analogs inhibit respiratory syncytial virus G protein function.
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.
authors.affiliation: Southern Research, Birmingham, AL, USA.
authors.forename: Carrie W
authors.initials: CW
authors.lastname: Evans
authors.affiliation: Southern Research, Birmingham, AL, USA.
authors.forename: Colm
authors.initials: C
authors.lastname: Atkins
authors.affiliation: Southern Research, Birmingham, AL, USA.
authors.forename: Ashish
authors.initials: A
authors.lastname: Pathak
authors.affiliation: Department of Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Gilbert
authors.affiliation: Southern Research, Birmingham, AL, USA. Electronic address: james.noah@nbacc.dhs.gov.
authors.forename: James W
authors.initials: JW
authors.lastname: Noah
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001562:Benzimidazoles / Q000494:pharmacology*; D002460:Cell Line; D004195:Disease Models, Animal; D024882:Drug Resistance, Viral; D057166:High-Throughput Screening Assays; D006801:Humans; D008826:Microbial Sensitivity Tests; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D018357:Respiratory Syncytial Virus Infections / Q000473:pathology / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000187:drug effects* / Q000502:physiology*; D016205:Sigmodontinae; D016019:Survival Analysis; D014759:Viral Envelope Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D053585:Virus Attachment / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D001562:Benzimidazoles; D050505:Mutant Proteins; D014759:Viral Envelope Proteins; C116204:attachment protein G; C031000:benzimidazole
keywords: Antiviral; G protein; Heparin; SAR; hRSV