Determination of Half-Maximal Inhibitory Concentration of an Enzyme Inhibitor

Drug development is the process of bringing a new pharmaceutical drug to the market once a lead compound has been identified through the process of drug discovery. Enzymes are one of the most important groups of drug targets; thus, enzyme inhibition is widely used for the treatment of certain disorders. The assessment of an inhibitor against an enzyme is predominantly based on two different parameters: the half-maximal inhibitory concentration (IC50) and the inhibition constant (Ki). This chapter describes an experimental procedure for the determination of the IC50 value of an enzyme inhibitor. The relationship between IC50 and Ki is also discussed.