Synergistic drug combination effectively blocks Ebola virus infection

•Drug combinations may enable clinical application by reducing individual drug concentrations for inhibiting EBOV infection.•795 pairs of three-drug combinations of FDA-approved drugs were screened for anti-Ebola virus activity.•Two sets of clinical useful three-drug combinations were validated for inhibition of live Ebola virus infection.•Mechanisms of action of these drugs were identified in affecting host-pathogen interactions.

Although a group of FDA-approved drugs were previously identified with activity against Ebola virus (EBOV), most of them are not clinically useful because their human blood concentrations are not high enough to inhibit EBOV infection. We screened 795 unique three-drug combinations in an EBOV entry assay. Two sets of three-drug combinations, toremifene-mefloquine-posaconazole and toremifene-clarithromycin-posaconazole, were identified that effectively blocked EBOV entry and were further validated for inhibition of live EBOV infection. The individual drug concentrations in the combinations were reduced to clinically relevant levels. We identified mechanisms of action of these drugs: functional inhibitions of Niemann-Pick C1, acid sphingomyelinase, and lysosomal calcium release. Our findings identify the drug combinations with potential to treat EBOV infection.