INHIBITORY EFFECTS OF SEPIMOSTAT MESILATE (FUT-187) ON THE ACTIVITIESOF TRYPSIN-LIKE SERINE PROTEASES IN-VITRO

Inhibitory activities of FUT-187 on trypsin-like serine proteases were compared using camostat mesilate (camostat), and 4-(4-guanidino benzo yloxy)phenyl acetic acid methanesulfonate(GBPA) known as an active met abolite of camostat in the blood. K-i values of FUT-187 on the competi tive inhibition mechanism were 0.097 mu M for trypsin, 0.029 mu M for pancreatic kallikrein, 0.61 mu M for plasma kallikrein, 0.57 mu M for plasmin, 2.5 mu M for thrombin, 20.4 mu M for factor Xa and 6.4 mu M f or C1(r) over bar. However, FUT-187 acted as a noncompetitive inhibito r for factor XIIa and an uncompetitive inhibitor for C1(s) over bar, a nd K-i values for these proteases were 0.021 and 0.18 mu M, respective ly. K-i values of camostat for these proteases were in the range of 0. 037 to 96.4 mu M, and those of GBPA for the above proteases except try psin and plasma kallikrein were higher than those of FUT-187. The inhi bitory activity of FUT-187 on trypsin was not reduced by the addition of the serum at 10%, whereas, that of GBPA was reduced (4.3 fold) in t erms of IC50 values. The concentration of FUT-187 required to double A PTT (activated partial thromboplastin time) was 1.09 mu M, while GBPA, by concentrations up to 1 mM failed to double APTT. The kinin formati on by glandular kallikrein in the rat plasma was inhibited by FUT-187 with IC50 value of 0.024 mu M, while camostat revealed no inhibition b y concentrations up to 1 mu M. The complement-mediated hemolyses in th e classical and alternative pathways were also inhibited by FUT-187 wi th IC50 values of 0.17 and 3.5 mu M, respectively, the corresponding v alues for camostat being 350 and 150 mu M, respectively. It is conclud ed that FUT-187 is a potent and selective inhibitor of trypsin-like se rine proteases, and its inhibitory activities are stronger than those of camostat on glandular kallikrein, factor XIIa and C1(s) over bar in complement pathway.