BTK and B-cell chronic lymphocytic leukemia: The BTK inhibitor ibrutinib (Imbruvica, Pharmacyclics, LLC), a first-generation BTK inhibitor which showed evidence of high efficacy and acceptable toxicity profile in clinical trials, was the first drug in this category to receive FDA approval as a single-agent frontline therapy for the B cell malignancies MCL, WM and CLL (including patients carrying del(17p) or TP53 mutation) [8].