R281 is a peptidic water soluble inhibitor that is cell impermeable and able to differentiate between TG2 and Factor XIIIa; ZDON is a commercial TG2 inhibitor that is TG2-specific and displays less effect on inhibiting TG1 and TG3 [20]; and 1-155 is a highly potent TG2-specific cell-permeable inhibitor that has shown effectiveness in inhabiting fibrosis and cancer progression [21,36,39,42]. The gene discussed is F13A1; the disease is cancer.