In human immunodeficiency virus type 1 (HIV-1) latently infected cells, NF-kappaB plays a major role in the transcriptional induction of HIV-1 replication. Hence, downregulation of NF-kappaB activation has long been sought for effective anti-HIV therapy. Tumor necrosis factor alpha (TNF-alpha) stimulates IkappaB kinase (IKK) complex, a critical regulator in the NF-kappaB signaling pathway. A novel IKK inhibitor, ACHP {2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl-nicotinonitrile}, was developed and evaluated as a potent and specific inhibitor for IKK-alpha and IKK-beta. In this study, we examined the ability of this compound to inhibit HIV-1 replication in OM10.1 cells latently infected with HIV. When these cells were pretreated with ACHP, TNF-alpha-induced HIV-1 replication was dramatically inhibited, as measured by the HIV p24 antigen levels in the culture supernatants. Its 50% effective concentration was approximately 0.56 microM, whereas its 50% cytotoxic concentration was about 15 microM. Western blot analysis revealed inhibition of IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 nuclear translocation, and p65 phosphorylation. ACHP was also found to suppress HIV-1 long terminal repeat (LTR)-driven gene expression through the inhibition of NF-kappaB activation. Furthermore, ACHP inhibited TNF-alpha-induced NF-kappaB (p65) recruitment to the HIV-1 LTR, as assessed by chromatin immunoprecipitation assay. These findings suggest that ACHP acts as a potent suppressor of TNF-alpha-induced HIV replication in latently infected cells and that this inhibition is mediated through suppression of IKK activity.