title: A Rapid Screening Assay Identifies Monotherapy with Interferon-ß and Combination Therapies with Nucleoside Analogs as Effective Inhibitors of Ebola Virus.
abstract: To date there are no approved antiviral drugs for the treatment of Ebola virus disease (EVD). While a number of candidate drugs have shown limited efficacy in vitro and/or in non-human primate studies, differences in experimental methodologies make it difficult to compare their therapeutic effectiveness. Using an in vitro model of Ebola Zaire replication with transcription-competent virus like particles (trVLPs), requiring only level 2 biosafety containment, we compared the activities of the type I interferons (IFNs) IFN-α and IFN-ß, a panel of viral polymerase inhibitors (lamivudine (3TC), zidovudine (AZT) tenofovir (TFV), favipiravir (FPV), the active metabolite of brincidofovir, cidofovir (CDF)), and the estrogen receptor modulator, toremifene (TOR), in inhibiting viral replication in dose-response and time course studies. We also tested 28 two- and 56 three-drug combinations against Ebola replication. IFN-α and IFN-ß inhibited viral replication 24 hours post-infection (IC50 0.038μM and 0.016μM, respectively). 3TC, AZT and TFV inhibited Ebola replication when used alone (50-62%) or in combination (87%). They exhibited lower IC50 (0.98-6.2μM) compared with FPV (36.8μM), when administered 24 hours post-infection. Unexpectedly, CDF had a narrow therapeutic window (6.25-25μM). When dosed >50μM, CDF treatment enhanced viral infection. IFN-ß exhibited strong synergy with 3TC (97.3% inhibition) or in triple combination with 3TC and AZT (95.8% inhibition). This study demonstrates that IFNs and viral polymerase inhibitors may have utility in EVD. We identified several 2 and 3 drug combinations with strong anti-Ebola activity, confirmed in studies using fully infectious ZEBOV, providing a rationale for testing combination therapies in animal models of lethal Ebola challenge. These studies open up new possibilities for novel therapeutic options, in particular combination therapies, which could prevent and treat Ebola infection and potentially reduce drug resistance.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Stephen D S
authors.initials: SD
authors.lastname: McCarthy
authors.affiliation: Division of Advanced Diagnostics, Infection and Immunity Group, Toronto General Research Institute, Toronto, Ontario, Canada.
authors.forename: Beata
authors.initials: B
authors.lastname: Majchrzak-Kita
authors.affiliation: Special Pathogens Program, National Microbiology Laboratory, Winnipeg, Manitoba, Canada.
authors.forename: Trina
authors.initials: T
authors.lastname: Racine
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hannah N
authors.initials: HN
authors.lastname: Kozlowski
authors.affiliation: Biogen, Cambridge, Massachusetts, United States of America.
authors.forename: Darren P
authors.initials: DP
authors.lastname: Baker
authors.affiliation: Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoenen
authors.affiliation: Special Pathogens Program, National Microbiology Laboratory, Winnipeg, Manitoba, Canada.
authors.forename: Gary P
authors.initials: GP
authors.lastname: Kobinger
authors.affiliation: Division of Advanced Diagnostics, Infection and Immunity Group, Toronto General Research Institute, Toronto, Ontario, Canada.|Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eleanor N
authors.initials: EN
authors.lastname: Fish
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.|Division of Advanced Diagnostics, Infection and Immunity Group, Toronto General Research Institute, Toronto, Ontario, Canada.|Centre for Innovation, Canadian Blood Services, Toronto, Ontario, Canada.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Branch
mesh_terms: D000998:Antiviral Agents / Q000008:administration & dosage / Q000494:pharmacology; D065100:CCR5 Receptor Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D003510:Cyclohexanes / Q000008:administration & dosage / Q000494:pharmacology; D029043:Ebolavirus / Q000187:drug effects*; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology*; D000077592:Maraviroc; D009705:Nucleosides / Q000627:therapeutic use*; D017312:Toremifene / Q000008:administration & dosage / Q000494:pharmacology; D014230:Triazoles / Q000008:administration & dosage / Q000494:pharmacology; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D065100:CCR5 Receptor Antagonists; D003510:Cyclohexanes; D009705:Nucleosides; D014230:Triazoles; D016899:Interferon-beta; D017312:Toremifene; D000077592:Maraviroc