BMS-509744 is a potent interleukin-2 inducible T cell kinase (ITK) inhibitor (IC50 = 19 nM). It displays 200-fold selectivity over Tec family kinases and 55-fold selectivity over other kinases tested. BMS-509744 reduces HIV infection of primary CD4+ T cells and attenuates the establishment of HIV infection in vitro. BMS-509744 also reduces T cell proliferation and IL-2 production in vitro. BMS-509744 reduces TCR-induced functions including PLCgamma1 tyrosine phosphorylation, calcium mobilization, IL-2 secretion, and T-cell proliferation in vitro in both human and mouse cells. BMS-509744 suppresses the production of IL-2 induced by anti-TCR antibody administered to mice. BMS-509744 also significantly diminishes lung inflammation in a mouse model of ovalbumin-induced allergy/asthma.