Pharmacodynamics (PD) is the branch of pharmacology that studies what a drug does to the body (‘what the drug does to the body’). It describes the biochemical and physiological effects of an active substance and its mechanism of action at a molecular level. PD studies analyze the relationship between the drug concentration at the site of action and the magnitude of the elicited response.
In early clinical trials (Phase I/II), PD measurements (often using biomarkers) are employed to demonstrate the biological activity of a new active substance, determine the appropriate dose, and confirm the mechanism of action in humans. They help to understand whether the drug achieves the desired biological effect. For CROs, integrating PD measurements into early studies is crucial for making informed decisions about the further development of an active substance.