MLN4924 is a first-in-class cancer drug that inhibits the Nedd8-activating enzyme (NAE). Herein, we report that MLN4924 inhibits Vpx/Vpr-induced SAMHD1 degradation by inhibiting the neddylation of E3 ubiquitin ligase and blocks macaque simian immunodeficiency virus (SIVmac) replication in myeloid cells.