DDX3X and infection: Since (1) DDX3X is an essential host co-factor for the replication of multiple viruses, (2) inhibitors of DDX3X can act as broad-spectrum antivirals [17,18] and (3) REN analogues have antiviral properties [19,20,21,22,23], we decided to test RK-33′s ability to inhibit infection by viruses belonging to the Paramyxoviridae and Flaviviridae families.