Nafamostat mesylate, previously known as FUT-175, is an inhibitor of serine protease that inhibits a variety of serine proteases, including trypsin and several proteases in the coagulation cascade. Although it was originally developed as an inhibitor of complements, Nafamostat mesylate has been widely used for the treatment of inflammation (such as acute pancreatitis) and disseminated intravascular coagulation (DIC). Nafamostat mesylate exhibits extremely potent inhibition against human tryptase as well as tryptase-catalyzed hydrolysis of Boc-Phe-Ser-Arg-MCA with inhibition constant Kivalue of 95.3 pM. Besides its protease-inhibiting activity, nafamostat mesylate, in a recent study, displayed its antimicrobial activity by dose-dependently inhibiting the proliferation of chlamydial in vitro.