Ibrutinib is a potent and highly selective Brutons tyrosine kinase (Btk) inhibitor with IC50 of 0.5 nM, modestly potent to Bmx, CSK, FGR, BRK, HCK, less potent to EGFR, Yes, ErbB2, JAK3, etc.

Bruton’s tyrosine kinase (BTK) is a member of the BTK/Tec family of protein tyrosine kinases involved in signal transduction pathways regulating proliferation, survival, migration, and tissue homing of B-cells.Ibrutinib is an irreversible inhibitor of BTK (IC50 = 0.5 nM) that selectively blocks B cell activation, promoting apoptosis and preventing homing to the protective tumor microenvironment, at concentrations that do not affect T cell receptor signaling (1,000-fold more potent).It has been reported to inhibit autophosphorylation of BTK (IC50 = 11 nM), phosphorylation of PLCγ (IC50 = 29 nM), a substrate of BTK, and phosphorylation of ERK (IC50 = 13 nM), a further downstream kinase.Its use has been examined clinically for the treatment of diseases associated with B cell antigen receptor signaling, including mantle cell lymphoma, chronic lymphocytic leukemia, and non-Hodgkin lymphoma.