Ibrutinib is the only once-daily oral inhibitor of Bruton’s tyrosine kinase (BTK) approved for treatment of CLL in the United States and European Union that has demonstrated significant progression-free survival (PFS) and overall survival (OS) benefit versus established therapies (including chemoimmunotherapy regimens) in randomized phase 3 studies in first-line CLL/small lymphocytic lymphoma (SLL) [2, 4, 5]. Here, BTK is linked to B-cell chronic lymphocytic leukemia.