Cyclooxygenase (COX)-2 and its products, including PGE2, are key inflammatory mediators. In this study, we have assessed the pharmacological characteristics of BAI, a 3-aminoindazole derivative and a novel cyclin-dependent kinase (CDK) inhibitor, for regulation of COX-2 expression induced by interleukin (IL)-1β in A549 human airway cells. Treatment with BAI strongly inhibited IL-1β-induced expression of COX-2 at both the protein and mRNA levels. Results of luciferase experiments also revealed that BAI treatment reduced IL-1β-induced COX-2 promoter activity. Distinctly, treatment with BAI did not affect IL-1β-induced phospho-rylation of extracellular signal-regulated protein kinase-1/2 (ERK-1/2), p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal protein kinase-1/2 (JNK-1/2) and proteolysis of IκB-α, an inhibitor of nuclear factor (NF)-κB, but inhibited IL-1β-induced phosphorylation of histone H1, a target for phosphorylation by CDKs. siRNA transfection experiments demonstrated that knockdown of CDK2 and CDK4 led to a slight reduction of IL-1β-induced histone H1 phosphorylation but had no effect on IL-1β-induced COX-2 expression. Interestingly, additional cell culture experiments showed the ability of BAI to repress the PMA-induced COX-2 expression in A549 cells and serum-dependent COX-2 expression in NCI-H292 cells, a human laryngeal cell line. Collectively, these results demonstrate firstly that BAI downregulates IL-1β-induced COX-2 expression through transcriptional repression, which appears to be independent of CDK2, CDK4, MAPKs and NF-κB, in A549 cells. It is suggested that BAI may be a potential candidate for treatment of the airway inflammatory diseases where COX-2 overexpression is problematic.