Synergistic antiviral activity against human adenovirus through combination of itraconazole and brincidofovir

Background and Purpose Human adenovirus (HAdV) causes respiratory or gastrointestinal tract infections depending on the virus subtype. While HAdV infections are generally self‐limiting in immunocompetent people, they can result in significant morbidity and mortality in immunocompromised adults and children. Due to the limited availability of effective therapeutic options, there is an urgent need for novel therapeutics to combat HAdV infection and mitigate its severity. Experimental Approach Here, we have repurposed the clinically well‐used antifungal, itraconazole, to control HAdV infection. We tested the antiviral potential of the itraconazole and the mTOR inhibitor Ku‐63794 on the production of infectious HAdV in A549 and Caco‐2 cells as well as human intestinal organoids (HIOs). Additionally, we evaluated the benefit of a combination of these host‐directed drugs with the direct‐acting antiviral brincidofovir. Key Results Pharmacological treatment with itraconazole significantly reduced virus titres in different in vitro models, including HIOs. Treatment with itraconazole impairs HAdV entry by entrapping incoming virus particles in endolysosomes and by promoting autophagy in HAdV‐infected cells. Moreover, combining itraconazole with brincidofovir, a cidofovir derivative currently under clinical evaluation for anti‐HAdV applications, demonstrated a synergistic effect in reducing HAdV titres. Conclusion and Implications Given the gastrointestinal toxicity associated with brincidofovir, its combination with the host‐directed drug itraconazole allowed lower brincidofovir doses to be used to decrease HAdV titres, thereby minimizing adverse drug effects while maintaining antiviral efficacy.