An update on the concept of Ligand Efficiency Indices (LEIs) — The early workflow based on ‘Efficiency Indices’ has been recently updated in a recent review published in Expert Opinion in Drug Discovery where a unifying LEIs formulation has been suggested. A review with the title Ligand Efficiency Indices for Effective Drug Discovery: a unifying vector formulation provides further details. The ideas presented have been developing since 2007 and growing from the early definitions of SEI, BEI, to a unifying vector formulation where SEI, BEI are the x and y components (respectively), of a Ligand Efficiency vector named vLEI (bold denotes vector). Details can be found in the recently published paper that can be found also in the ‘AtlasCBS’ and ‘News’ tabs.