Determination of serum protein binding affinity of inhibitors from analysis of concentration-response plots in biochemical activity assays.

Serum protein binding is a common problem with synthetic molecules designed as enzyme and receptor inhibitors for in vivo clinical use. The theoretical basis of a simple method is described. In this method, the dissociation constant for serum protein binding may be determined from analysis of the shift in apparent IC(50) (concentration at which 50% inhibition of activity is observed) caused by the presence of varying concentrations of serum (or individual serum proteins) in biochemical activity assays. Knowledge of the serum protein dissociation constant and the serum concentration of the binding protein can be used to predict the amount of free compound available in vivo after dosing to achieve a specific total concentration of compound in the blood stream. Copyright 2000 Wiley-Liss, Inc.