ITK and hepatocellular carcinoma: Besides inhibiting BTK, ibrutinib also irreversibly inhibits various other kinases which contain a cysteine residue aligning with C481 in BTK, including but not limited to tyrosine kinase expressed in hepatocellular carcinoma (TEC), interleukin-2-inducible T-cell kinase (ITK), and epidermal growth factor receptor (EGFR) (48).