CC6 – Drug affinity

CC6. Drug affinity is the binding strength of a drug to a target.

6.1. Binding of drugs to receptors obeys the law of mass action.

6.2. Affinity is commonly quantified through the determination of the equilibrium dissociation constant (Kd) and is formally defined as the ratio of the dissociation rate constant to the association rate constant.

6.3. The lower the value of Kd, the lower the concentration of drug required to occupy a proportion of target, and the higher the affinity

6.4. The structure of a drug molecule and the conformation of the target determines affinity.

6.5. The affinity of a drug can change as a consequence of the binding of an allosteric modulator.