Nafamostat mesilate is an extremely potent inhibitor of human tryptase.

Previously, nafamostat mesilate was found to be a potent inhibitor of human tryptase. In present study, we performed a kinetic study to determine its K(i) value for tryptase and compared it with that of gabexate mesilate. Nafamostat mesilate inhibited human tryptase in a competitive manner. The apparent K(i) value was estimated to be 95.3 pM, which was 1000 times lower than that of gabexate mesilate (95.1 nM). These results strongly indicated that nafamostat mesilate is an extremely potent inhibitor of tryptase and suggested that some of its beneficial effects in the treatment of clinical status may be due to tryptase inhibition.