The FDA has approved the use of the irreversible BTK inhibitors ibrutinib (first generation) in chronic lymphatic leukemia (CLL), mantle cell lymphoma (MCL), Waldenstrom macroglobulinemia (WM), and graft vs. host disease (10) and acalabrutinib (more selective, second generation) in MCL (11). This evidence concerns the gene BTK and B-cell chronic lymphocytic leukemia.