European Chemical Biology Library (ECBL) / Pilot Library

The aim of the pilot library is to provide a small but characteristic collection of the entire library which can be used by scientific collaborators for estimation of hit rates, and to evaluate the robustness of their biological assays. In addition, the library contains a large collection of well characterized compounds with known bioactivities which offer a good chance of finding active compounds for novel biological targets (repurposing). In total, the pilot screening library consists of nearly 5,000 compounds.

The selection of the ECBL representative compounds was based on similarity calculations using a Tanimoto coefficient. This included a random selection of plates sets with 352 compounds in each plate, and a calculation of mean similarities per plate set. Out of these, seven plates were selected which showed a mean value (~ 0.67) close to the mean values from all plate sets (shown with red dots in the Figure below), resulting in a total of 2,464 compounds.

The bioactives part of the library, again consisting of seven plates with 2,464 compounds, was designed by Ctibor Skuta / Petr Bartunek from the EU-OPENSCREEN partner site IMG in Prague. A strong emphasis was put on the selection of molecules with high target selectivity. The compounds are active against 1,039 different targets, among them 654 approved drugs and 368 highly selective probes from the public domain.

A graphical overview about target and pathway coverage is shown in the Figure below and was generated using the Probes & Drugs portal ( All these compounds are now available for research projects which can be carried out in collaboration with one of our screening partner sites.