An important part of the classical drug discovery paradigm is the cell based assay. Medicinal chemists, after identification of the molecular target such as enzyme or receptor are quite efficient with the design and synthesis of a potential inhibitor or receptor antagonist. If crystal structure of the target proteins is available, computer modeling accelerated the overall process substantially. Also the combinatorial libraries could supply a large number of interesting new chemical structures. In a relative short time, medicinal chemistry could create a large number of the potent inhibitors or receptor antagonists.