binding constant half maximal effective concentration (EC50) equilibrium dissociation constant (KD) approximated by EC50 A measurement of an EC50 value under specific assay conditions approximates KD, namely the binding reaction is at an equilibrium, and the concentration of the receptor must be much less than the KD for the ligand. Assay Development: Fundamentals and Practices, By Ge Wu, page 74 PERSON: Bjoern Peters, Randi Vita equilibrium dissociation constant (KD) approximated by EC50 metadata complete