The below discussion assumes some familiarity with terminology from medicinal chemistry. Briefly: medicinal chemists commonly rely on parameters such as IC 50 , EC 50 , logD 7.4 , permeability, and efflux ratio to guide the optimization of pharmacokinetic and pharmacodynamic properties. The IC 50 value quantifies the concentration of a compound needed for half-maximal inhibition of a specific enzyme or pathway, while the EC 50 is the concentration at which half the maximal effect (e.g., in a cellular or functional assay) is observed-lower values of either indicate higher potency or efficacy. LogD is the distribution coefficient (often measured at a specific pH, such as 7.4) between n-octanol and water: higher values indicate that a compound is more lipophilic, while lower values indicate that a compound is more hydrophilic. The efflux ratio, often measured in polarized cell monolayer assays such as the human Caco-2 cell line, captures how readily a compound is transported out of cells. In such assays, the apparent permeability from the apical to basolateral side (P app (A → B)) is compared to the permeability in the reverse direction (P app (B → A)). A high efflux ratio suggests active pumping by transporters like P-glycoprotein (P-gp), an ATP-dependent efflux transporter.