Targeting BTK activity via small molecule covalent inhibitors like ibrutinib has also shown therapeutic efficacy in B cell malignancies associated with dysfunctional BCR signaling including mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) (Advani et al. 2013; Hendriks et al. 2014). Here, BTK is linked to B-cell chronic lymphocytic leukemia.