4-Chlorophenylguanidine hydrochloride is a potent and selective inhibitor of urokinase [1].

Urokinase is a serine protease. Its primary physiological substrate is plasminogen, which is an inactive form of plasmin. Urokinase plays an important role in vascular diseases and cancer.

4-Chlorophenylguanidine hydrochloride inhibited urokinase and trypsin with Ki value of 6.07 μM and 120 μM, respectively [1].

Reference:
[1].  Yang H, Henkin J, Kim KH, et al. Selective inhibition of urokinase by substituted phenylguanidines: quantitative structure-activity relationship analyses. J Med Chem, 1990, 33(11): 2956-2961.