ITK and hepatocellular carcinoma: Ibrutinib has the propensity to bind to other enzymatic structures similar to BTK that contain the target cysteine residue, such as IL-2-inducible T cell kinase (ITK), tyrosine kinase expressed in hepatocellular carcinoma (TEC), and hematopoietic cell kinase (HCK), resulting in off-target effects (107).