Ibrutinib, the first approved Bruton ́s Tyrosine Kinase (BTK) inhibitor, has shown potent clinical activity in a variety of B-cell malignancies and has been globally approved for the treatment of adult patients with Chronic Lymphocytic Leukemia (CLL) and Small Lymphocytic Lymphoma (SLL) [1]. This evidence concerns the gene BTK and B-cell chronic lymphocytic leukemia.