BTK and B-cell chronic lymphocytic leukemia: Subsequent major breakthroughs in the development of drugs for NHL and CLL have come from the introduction of B-cell receptor antagonizing agents, such as ibrutinib, which targets Bruton’s tyrosine kinase (BTK), and idelalisib, which targets the delta isoform of phosphatidylinositol 3-kinase (PI3Kδ) [3–7].