Mechanisms of action

In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor. Receptor sites have specific affinities for drugs based on the chemical structure of the drug, as well as the specific action that occurs there. Drugs that do not bind to receptors produce their corresponding therapeutic effect by simply interacting with chemical or physical properties in the body. Common examples of drugs that work in this way are antacids and laxatives.

In comparison, a mode of action (MoA) describes functional or anatomical changes, at the cellular level, resulting from the exposure of a living organism to a substance.

Elucidating the mechanism of action of novel drugs and medications is important for several reasons:

Bioactive compounds induce phenotypic changes in target cells, changes that are observable by microscopy, and which can give insight into the mechanism of action of the compound. With antibacterial agents, for example, the conversion of target cells to spheroplasts can be an indication that peptidoglycan synthesis is being targeted, and filamentation of target cells can be an indication that FtsZ or DNA is being targeted. In the case of anticancer agents, bleb formation can be an indication that the compound is disrupting the plasma membrane. A current limitation of this approach is the time required to manually generate and interpret data, but advances in automated microscopy and image analysis software may help resolve this.

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