Binding Affinity

Also called Ki · EC50 · IC50 · receptor affinity · binding constant

Binding affinity describes the strength of the interaction between a compound and its receptor. Ki (inhibition constant) measures binding strength in displacement assays — lower Ki means tighter binding. EC₅₀ (half-maximal effective concentration) is the concentration that produces 50% of maximum receptor activation. These metrics appear in pharmacology papers and are central to comparing selectivity across receptor subtypes — for example, tirzepatide's GIP-R affinity relative to its GLP-1R affinity.