Tyrphostin A1(AG9) inhibits CD40L-stimulated IL-12 production in macrophage cultures and antigen-induced generation of Th1 cells. IC50 value: Target: IL-12 production inhibitor Addition of increasing concentration of A1 resulted in a dose dependent decrease of IL-12 p40, with maximal inhibition (62.5%) occurring at a dose of 10 μM. tyrphostin A1 blocks CD40L-induced translocation of NF-κB to the nucleus, and reduces the activation of IL-12 p40 gene. In vivo therapy with A1 leads to decrease in generation of myelin basic protein (MBP) specific encephalitogenic T cells. In addition, treatment of SJL/J mice with A1 results in attenuation of experimental allergic encephalomyelitis (EAE) [1]. Tyrphostin A1 is a much weaker inhibitor of TK than other tyrphostins (IC50>1250 μM for epidermal growth factor receptor (EGFR) kinase), and therefore often used to differentiate TK-mediated effects of tyrphostins from other non-specific effects [2].