In Vitro Activity of Itraconazole Against SARS-CoV-2

Van Damme, Ellen; De Meyer, Sandra; Bojkova, Denisa; Ciesek, Sandra; Cinatl, Jindrich; De Jonghe, Steven; Jochmans, Dirk; Leyssen, Pieter; Buyck, Christophe; Neyts, Johan; Van Loock, Marnix

Background As long as there is no vaccine available, having access to inhibitors of SARS-CoV-2 will be of utmost importance. Antivirals against coronaviruses do not exist, hence global drug re-purposing efforts have been carried out to identify agents that may provide clinical benefit to patients with COVID-19. Itraconazole, an antifungal agent, has been reported to have potential activity against animal coronaviruses. Methods Using cell-based phenotypic assays, the in vitro antiviral activity of itraconazole and 17-OH itraconazole was assessed against clinical isolates from a German and Belgian patient infected with SARS-CoV-2. Results Itraconazole demonstrated antiviral activity in human Caco-2 cells (EC50 = 2.3 μM; MTT assay). Similarly, its primary metabolite, 17-OH itraconazole, showed inhibition of SARS-CoV-2 activity (EC50 = 3.6 μM). Remdesivir inhibited viral replication with an EC50 = 0.4 μM. Itraconazole and 17-OH itraconazole resulted in a viral yield reduction in vitro of approximately 2-log10 and approximately 1-log10, as measured in both Caco-2 cells and VeroE6-eGFP cells, respectively. The viral yield reduction brought about by remdesivir or GS-441524 (parent nucleoside of the antiviral prodrug remdesivir; positive control) was more pronounced, with an approximately 3 log10 drop and >4 log10 drop in Caco-2 cells and VeroE6-eGFP cells, respectively. Discussion Itraconazole and 17-OH itraconazole exert in vitro low micromolar activity against SARS-CoV-2. Despite the in vitro antiviral activity, itraconazole did not result in a beneficial effect in hospitalized COVID-19 patients in a clinical study (EudraCT Number: 2020-001243-15). Highlights Itraconazole exerted in vitro low micromolar activity against SARS-CoV-2 (EC50 = 2.3 μM) Remdesivir demonstrated potent antiviral activity, confirming validity of the assay Itraconazole has since shown no efficacy in a clinical study in hospitalized COVID-19 patients