What the compound does to the body — how it works, what it activates, what changes as a result.Covers receptor binding, mechanism of action, downstream biological effects, and dose-response relationships. A complete pharmacological characterization requires both pharmacodynamics (what the drug does) and pharmacokinetics (what the body does to the drug). PD data from in vitro assays tells you the compound can activate a receptor; PD data from human trials tells you what happens when it does so in a complex physiological system.