Ibrutinib, an irreversible inhibitor of BTK, is now approved for the treatment of chronic lymphocytic leukemia (B-CLL) [76, 77], mantle cell lymphoma [78], marginal zone lymphoma [79], small lymphocytic lymphoma [80] and Waldenström’s macroglobulinemia [81]. Here, BTK is linked to B-cell chronic lymphocytic leukemia.