EC50

Definition

EC50 (half maximal effective concentration) is the molar concentration of an agonist compound that produces 50% of the maximum achievable response (Emax) in a defined biological assay or animal model. It is the primary metric for characterizing agonist potency and is determined by fitting dose-response data to the Hill equation or sigmoidal Emax model. EC50 values are assay-specific: the same compound can have different EC50 values in different cell lines, tissue preparations, or species depending on receptor density, signaling efficiency, and system amplification. Lower EC50 values indicate greater potency.

Research Context

EC50 is a fundamental parameter in preclinical peptide research for comparing compound potency across analogs or characterizing structure-activity relationships. For growth hormone secretagogues such as CJC-1295/Ipamorelin, EC50 values from GH release assays in pituitary cell culture characterize relative potency compared to native GHRH. For neuroprotective compounds such as Semax, EC50 values from BDNF induction or neuroprotection assays quantify efficacy. EC50 values are typically reported alongside Emax values to fully characterize a compound's potency and maximal efficacy.