Abstract Details

Poster 13: High-Throughput Screening Case Studies for the Successful Identification of Ion Channel Ligands

Alexander Böcker1, Pierre Ilouga1, Sabine Schaertl1, Insa Winzenborg1, Stephen Hess1, Annett Müller1
1Evotec AG, Essener Bogen 7, 22419 Hamburg, Germany
At Evotec a carefully selected maximum diversity library of more than 250,000 lead-like compounds is readily available for HTS and has been applied to the screening of several ion channel targets. Highly robust cell-based FLIPR1 assays with kinetic read-outs have been developed as indicated by excellent Zí values above 0.7.2 Automated analysis scripts were developed in the statistical programming language R to fully capitalize on the measured kinetic traces, discriminate potential Agonists from Antagonists, identify autofluorescent compounds or correct for potential edge effects. Selective applications will be demonstrated.

A key finding of our approach is that ion channel HTS are able to successfully identify sufficiently large sets of potential agonists and antagonists. This outcome is supported by confirmation of the hits using manual and automated patch-clamp measurements. Chemical space analyses of the screening collection have been performed using principle component analysis (PCA), clustering3 and self organizing maps4 in combination with MOE physicochemical descriptors5 or chemical fingerprints.6 The identified ion channel ligands have been compared to compounds detected as hits by cell-based HTS assays for G protein coupled receptor ligands. Our analyses show that ion channel HTS hits are highly diverse and broadly cover a drug-like physicochemical property space. Various key physicochemical properties were further studied individually. A paucity of low molecular weight ion channel HTS hits with low lipophilicity was observed. This observation is not obvious for GPCR HTS hits.

In conclusion we would like to emphasize that HTS against ion channel targets requires detailed knowledge of the biophysical and pharmacological properties of the channel pharmacology. Careful assay setup and HTS data analysis is required to detect and eliminate sources of false positives. This allows the successful identification of ion channel ligands for subsequent hit-to-lead programs. Chemical space analyses demonstrate that highly diverse sets of potential ligands can be expected and reveal the possibility of using logP/logD7 and molecular weight as triaging filter for HTS hit sets.

(1) Molecular Devices, LLC, Sunnyvale, USA, 2012.
(2) Zhang, J. H., Chung, T. D. Y. & Oldenburg, K. R. J. Biomol. Screen. (1999), 4, 67-73.
(3) Weizhong, L. J. Chem. Inf. Mod. (2006) 46, 1919-1923.
(4) Ultsch, A. & Moerchen, F. Technical Report Dept. of Mathematics and Computer Science, University of Marburg, Germany, No. 46, (2005).
(5) Molecular Operating EnVironment (MOE), Version 2011.10; Chemical Computing Group Inc.: Montreal, Canada, 2011.
(6) SYBYLX version 1.2; Tripos International: St Louis, USA, 2009.
(7) JChem, Version 5.9; ChemAxon Ltd.: Budapest, Hungary, 2012.

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