Ibrutinib, a first-in-class BTK drug, has been attributed to an increased population of activated T cells and diminished levels of Treg/CD4+ T cell ratio while imparting its immunomodulatory effects against CLL through inhibition of BTK and IL-2-inducible T cell kinase (ITK) [106]. This evidence concerns the gene ITK and B-cell chronic lymphocytic leukemia.