Inhibitors of the protease domain of urokinase-type plasminogen activator.

Human urokinase-type plasminogen activator (uPA or uPA) has been implicated in the regulation and control of basement membrane and interstitial protein degradation. Since Urokinase plays a role in tissue remodeling, it may be responsible, in part, for the disease progression of cancer. Inhibitors of urokinase may then be useful in the treatment of cancer by retarding tumor growth and metastasis. Urokinase is a multidomain protein, two regions of the protein are most responsible for the observed proteolytic activity in cancer disease and progression. The N-terminal domain or ATF binds to a Urokinase receptor (uPAR) on the cell surface and the C-terminal serine protease domain, then, activates plasminogen to plasmin, beginning a cascade of events leading to the progression of cancer. Investigations of urokinase inhibition has been an area of ongoing research for the past 3 decades. It began with the discovery of small natural and unnatural amino acid derivatives or peptide analogs which exhibited weak inhibition of uPA. The last decade has seen the generation of several classes of potent and selective Urokinase inhibitor directed to the serine protease domain of the protein which have shown potential anti-cancer effects. The availability of structural information of enzyme-inhibitor complexes either by nuclear magnetic spectroscopy (NMR) or crystallography has allowed a detailed analysis of inhibitor protein interactions that contribute to observed inhibitor potency. Structural studies of specific inhibitor-uPA complexes will be discussed as well as the contributions of specific inhibitor protein interactions that are important for overall inhibitor potency. These data were used to discover a class of urokinase inhibitor based on the 2-Naphthamidine template that exhibits potent urokinase inhibition and excellent selectivity for urokinase over similar trypsin family serine proteases.