How do you calculate IC50 of an inhibitor?

IC50, or the half-maximal inhibitory concentration, is calculated by determining the concentration of an inhibitor that decreases the activity of a target (like an enzyme or receptor) by 50%. To calculate it, you typically perform a dose-response assay, measuring the activity at various concentrations of the inhibitor. Plot the data on a graph with inhibitor concentration on the x-axis and percentage of activity on the y-axis. The IC50 is then identified from the curve as the concentration at which the activity is reduced to 50%.