Both CLQ-OH and ATM are repositioned drugs and their antiviral mechanism of action, particularly in combination, remains mostly unclear. In vitro studies have shown that CLQ-OH inhibits SARS-CoV-2 [4], [5], [6]. Far less is known about the antiviral effects of ATM, which has been suggested to interfere with influenza virus internalization [7]. Interestingly, CLQ is also considered as an inhibitor of endocytic pathways through an elevation of endosomal pH [8]. However, several reports indicate that CLQ could also prevent virus attachment through a direct effect on host-cell surface molecules [9,10].