Ibrutinib, a first-in-class BTK drug, has been attributed to an increased population of activated T-cells and diminished Treg/CD4+ T-cell ratios while imparting its immunomodulatory effects against CLL through the inhibition of BTK and IL-2-inducible T-cell kinase (ITK) [102]. The gene discussed is ITK; the disease is B-cell chronic lymphocytic leukemia.