Purity >97%. Bruton's tyrosine kinase (BTK) is a member of the BTK/Tec family of protein tyrosine kinases involved in signal transduction pathways regulating growth and differentiation of B cells. BTK acts as an inhibitor of Fas/APO-1-mediated apoptosis in B cells by preventing FAS-FADD interaction. LFM-A13 is an anti-leukemia agent with apoptosis-promoting and chemosensitizing properties. It acts as an inhibitor of Bruton's tyrosine kinase (BTK) and Polo-like kinase (Plk) with IC50 values of 2.5 μM (mouse recombinant) and 10 μM (Xenopus), respectively. LFM-A13 exhibits minor inhibitory activity against a number of other protein kinases including JAK1, JAK2, EGFR, IRK, IKK, and Cdk1, 2 and 3, as well as several other related kinases. LFM-A13 also exhibits anti-proliferative activity against HER2/Neu-overexpressing breast cancer cells.