Identification of Clotrimazole Derivatives as Specific Inhibitors of Arenavirus Fusion.

Torriani, Giulia; Trofimenko, Evgeniya; Mayor, Jennifer; Fedeli, Chiara; Moreno, Hector; Michel, Sébastien; Heulot, Mathieu; Chevalier, Nadja; Zimmer, Gert; Shrestha, Neeta; Plattet, Philippe; Engler, Olivier; Rothenberger, Sylvia; Widmann, Christian; Kunz, Stefan (2019). Identification of Clotrimazole Derivatives as Specific Inhibitors of Arenavirus Fusion. Journal of virology, 93(6) American Society for Microbiology 10.1128/JVI.01744-18

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Arenaviruses are a large family of emerging enveloped negative-strand RNA viruses that include several causative agents of viral hemorrhagic fevers. For cell entry, human-pathogenic arenaviruses use different cellular receptors and endocytic pathways that converge at the level of acidified late endosomes, where the viral envelope glycoprotein mediates membrane fusion. Inhibitors of arenavirus entry hold promise for therapeutic antiviral intervention and the identification of "druggable" targets is of high priority. Using a recombinant vesicular stomatitis virus pseudotype platform, we identified the clotrimazole-derivative TRAM-34, a highly selective antagonist of the calcium-activated potassium channel KCa3.1, as a specific entry inhibitor for arenaviruses. TRAM-34 specifically blocked entry of most arenaviruses, including hemorrhagic fever viruses, but not Lassa virus and other enveloped viruses. Anti-arenaviral activity was likewise observed with the parental compound clotrimazole and the derivative senicapoc, whereas structurally unrelated KCa3.1 inhibitors showed no antiviral effect. Deletion of KCa3.1 by CRISPR/Cas9 technology did not affect the antiarenaviral effect of TRAM-34, indicating that the observed antiviral effect of clotrimazoles was independent of the known pharmacological target. The drug affected neither virus-cell attachment, nor endocytosis, suggesting an effect on later entry steps. Employing a quantitative cell-cell fusion assay that bypasses endocytosis, we demonstrate that TRAM-34 specifically inhibits arenavirus-mediated membrane fusion. In sum, we uncover a novel antiarenaviral action of clotrimazoles that currently undergo in vivo evaluation in the context of other human diseases. Their favorable in vivo toxicity profiles and stability opens the possibility to repurpose clotrimazole derivatives for therapeutic intervention against human-pathogenic arenaviruses.IMPORTANCE Emerging human-pathogenic arenaviruses are causative agents of severe hemorrhagic fevers with high mortality and represent serious public health problems. The current lack of a licensed vaccine and the limited treatment options makes the development of novel antiarenaviral therapeutics an urgent need. Using a recombinant pseudotype platform, we uncovered that clotrimazole drugs, in particular TRAM-34, specifically inhibit cell entry of a range of arenaviruses, including important emerging human pathogens, with the exception of Lassa virus. The antiviral effect was independent of the known pharmacological drug target and involved inhibition of the unusual membrane fusion mechanism of arenaviruses. TRAM-34 and its derivatives currently undergo evaluation against a number of human diseases and show favorable toxicity profiles and high stability in vivo Our study provides the basis for further evaluation of clotrimazole derivatives as antiviral drug candidates. Their advanced stage of drug development will facilitate repurposing for therapeutic intervention against human-pathogenic arenaviruses.

Item Type:

Journal Article (Original Article)


05 Veterinary Medicine > Department of Infectious Diseases and Pathobiology (DIP) > Institute of Virology and Immunology
05 Veterinary Medicine > Department of Infectious Diseases and Pathobiology (DIP)

UniBE Contributor:

Zimmer, Gert


500 Science > 570 Life sciences; biology
600 Technology > 630 Agriculture




American Society for Microbiology




Pamela Schumacher

Date Deposited:

04 Sep 2019 16:28

Last Modified:

05 Dec 2022 15:30

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

antiviral agents arenavirus emerging virus fusion inhibitor viral entry viral fusion viral hemorrhagic fever




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