Ligand Efficiency (LE)

A metric that normalizes binding affinity by molecular size, typically calculated as delta-G divided by the number of non-hydrogen (heavy) atoms. Ligand efficiency helps medicinal chemists compare fragments and leads of different sizes on an equal footing, guiding optimization toward potent yet drug-like molecules. Values above 0.3 kcal/mol per heavy atom are generally considered efficient.

Exemples

• Fragment hits with LE > 0.4 kcal/mol/HA are prioritized for optimization
• LLEAT (Ligand-Lipophilic Efficiency) adjusts for lipophilicity (pIC50 - cLogP)
• BEI (Binding Efficiency Index) = pIC50/MW in kDa