TFPI(Tissue factor pathway inhibitor) is a Kunitz-type serine protease inhibitor that regulates the tissue factor (TF)-dependent pathway of blood coagulation.TFPI plays a crucial role in regulating the extrinsic pathway of blood coagulation, which is vital for maintaining hemostasis and preventing excessive bleeding. TFPI functions by directly inhibiting factor Xa and, in an Xa-dependent manner, also inhibits the catalytic complex formed by factor VIIa and tissue factor, thereby preventing the propagation of coagulation. This regulation is particularly important in pathological conditions where tissue factor is aberrantly expressed, such as in cancer and inflammatory diseases, as TFPI helps to control thrombus formation and maintain vascular integrity.