BTK and mantle cell lymphoma: The Food and Drug Administration (FDA) approval of the first covalent BTK inhibitor (cBTKi), ibrutinib, for mantle cell lymphoma (MCL), chronic lymphocytic leukemia (CLL), and Waldenström’s macroglobulinemia (WM) marked the beginning of a chemotherapy-free era in the management of B-cell malignancies [5–7].