BTK and B-cell chronic lymphocytic leukemia: Novel targeted agents including inhibitors of Bruton’s tyrosine kinase (BTK), apoptosis regulator B-cell leukemia/lymphoma 2 (BCL-2), and phosphatidylinositol-4,5-bis-phosphate 3-kinase catalytic subunit delta (PI3Kδ) have greatly changed the landscape in the treatment of CLL (5–7).