The most recent Ebola virus outbreak in West Africa, which was unprecedented in the number of cases and fatalities, geographic distribution, and number of nations affected, highlights the need for safe, effective, and readily available antiviral agents for treatment and prevention of acute Ebola virus (EBOV) disease (EVD) or sequelae1. No antiviral therapeutics have yet received regulatory approval or demonstrated clinical efficacy. Here we report the discovery of a novel small molecule GS-5734, a monophosphoramidate prodrug of an adenosine analogue, with antiviral activity against EBOV. GS-5734 exhibits antiviral activity against multiple variants of EBOV and other filoviruses in cell-based assays. The pharmacologically active nucleoside triphosphate (NTP) is efficiently formed in multiple human cell types incubated with GS-5734 in vitro, and the NTP acts as an alternative substrate and RNA-chain terminator in primer-extension assays using a surrogate respiratory syncytial virus RNA polymerase. Intravenous administration of GS-5734 to nonhuman primates resulted in persistent NTP levels in peripheral blood mononuclear cells (half-life, 14 h) and distribution to sanctuary sites for viral replication including testes, eyes, and brain. In a rhesus monkey model of EVD, once-daily intravenous administration of 10 mg kg−1 GS-5734 for 12 days resulted in profound suppression of EBOV replication and protected 100% of EBOV-infected animals against lethal disease, ameliorating clinical disease signs and pathophysiological markers, even when treatments were initiated three days after virus exposure when systemic viral RNA was detected in two out of six treated animals. These results show the first substantive post-exposure protection by a small-molecule antiviral compound against EBOV in nonhuman primates. The broad-spectrum antiviral activity of GS-5734 in vitro against other pathogenic RNA viruses, including filoviruses, arenaviruses, and coronaviruses, suggests the potential for wider medical use. GS-5734 is amenable to large-scale manufacturing, and clinical studies investigating the drug safety and pharmacokinetics are ongoing.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Viral genomic sequences have been deposited in GenBank (http://www.ncbi.nlm.nih.gov/genbank/) and accession numbers are supplied in Extended Data Table 5. Small molecule X-ray crystallographic coordinates and structure factor files have been deposited in the Cambridge Structural Database (http://www.ccdc.cam.ac.uk/) and accession numbers are supplied in the Supplementary Information.
T. Bocan, A. Duplantier, R. Panchal, and C. Kane provided scientific input. B. Norquist assisted with manuscript preparation. C. Cooper provided scientific input with human macrophage cultures for high-content image assessments. S. Tritsch and G. Gomba assisted with GS-5734 dose preparations for efficacy studies. C. Rice provided animal husbandry support services. X. Wei, W. Garner, and L. Zhong provided additional support for statistical analyses. K. Wang, K. Brendza, T. Alfredson, and L. Serafini assisted with analytical methods; S. Bondy and R. Seemayer procured key raw materials; L. Heumann, R. Polniaszeck, E. Rueden, A. Chtchemelinine, K. Brak, and B. Hoang contributed to synthesis; and Y. Zherebina helped with chiral separations. G. Lee supported the RSV antiviral assay, and G. Stepan, S. Ahmadyar, and H. Yu conducted part of the cytotoxicity testing. J. Knox contributed to polymerase modelling. A. L. Rheingold performed the X-ray crystallographic analysis (Supplementary Information). Studies at USAMRIID were in part supported by The Joint Science and Technology Office for Chemical and Biological Defense (JSTO-CBD) of the Defense Threat Reduction Agency (DTRA) under plan #CB10218. Work in the Fearns laboratory was supported by NIH R01AI113321. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the US Army or the Centers for Disease Control and Prevention, US Department of Health and Human Services.
Extended data figures
Extended data tables
This file contains Supplementary Methods describing the synthesis of GS-5734 and the analytical data that support the synthetic steps.
This file contains (1) Supplementary Figure, which shows the labeled uncropped gel depicted in Figure 1f and (2) Supplementary Table 1, which shows the list of primary and secondary antibodies used in immunostaining assay.
About this article
Nature Reviews Drug Discovery (2018)