Iminosugars are host-directed antivirals that inhibit glycosylation pathways. Iminosugar analogs based on NB-DNJ demonstrated in vitro activity against live EBOV and MARV. In vivo efficacy studies provided inconsistent data following treatment with iminosugars using filovirus mouse models. UV-4B did not provide clinical benefit in a small proof-of-concept macaque efficacy trial when dosed once per day.