BTK and B-cell chronic lymphocytic leukemia: Although BTK is a target for the treatment of chronic lymphocytic leukemia (4, 9–13), the utility of currently approved irreversible BTK inhibitors such as ibrutinib, acalabrutinib, and zanubrutinib has been limited by acquired resistance and the occurrence of side effects mediated by off-target engagement of kinases, including ITK, TEC, and EGFR (12–14).