Ligand efficiency is a measurement of the binding energy per atom of a ligand to its binding partner, such as a receptor or enzyme.
Ligand efficiency is used in drug discovery research programs to assist in narrowing focus to lead compounds with optimal combinations of physicochemical properties and pharmacological properties.
Mathematically, ligand efficiency (LE) can be defined as the ratio of Gibbs free energy (ΔG) to the number of non-hydrogen atoms of the compound:
:LE = -(ΔG)/N
where ΔG = −RTlnK and N is the number of non-hydrogen atoms. It can be transformed to the equation:
:LE = 1.4(−log IC)/N