Screening and evaluation of potential inhibitors against vaccinia virus from 767 approved drugs

: The development of therapies for human smallpox is needed due to the increasing concern over the potential use of smallpox virus as a biological weapon. Here, we report a high-throughput screening for anti-smallpox virus drugs from a 767-small-molecule library, employing two vaccinia virus (VACV) strains containing firefly luciferase (VTT-Fluc and VG9-Fluc) as surrogate viruses. Using an eight-point dose response format assay, 26 compounds of different pharmacological classes were identified with in vitro anti-VACV activities. Mycophenolate mofetil (MMF) and tranilast (TRA) were detected to possess the highest anti-VACV potency (selectivity index values of >334 and >74, respectively); they could inhibit VTT-Fluc replication in nude mice at 5 days post-infection by 99% (10 mg/kg, P < .01) and 59% (45 mg/kg, P = .01), respectively, as indicated by bioluminescent intensity. In conclusion, MMF and TRA are promising anti-smallpox virus candidates for further optimization and repurposing for use in clinical practice.