title: A False-Positive Screening Hit in Fragment-Based Lead Discovery: Watch out for the Red Herring.
abstract: With the rising popularity of fragment-based approaches in drug development, more and more attention has to be devoted to the detection of false-positive screening results. In particular, the small size and low affinity of fragments drives screening techniques to their limit. The pursuit of a false-positive hit can cause significant loss of time and resources. Here, we present an instructive and intriguing investigation into the origin of misleading assay results for a fragment that emerged as the most potent binder for the aspartic protease endothiapepsin (EP) across multiple screening assays. This molecule shows its biological effect mainly after conversion into another entity through a reaction cascade that involves major rearrangements of its heterocyclic scaffold. The formed ligand binds EP through an induced-fit mechanism involving remarkable electrostatic interactions. Structural information in the initial screening proved to be crucial for the identification of this false-positive hit.
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cramer
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schiebel
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wulsdorf
authors.affiliation: Abteilung für NMR-basierte Strukturbiologie, Max Planck Institut für Biophysikalische Chemie, Am Faßberg 11, 37077, Göttingen, Germany.|Fakultät für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Haus F, 81377, München, Germany.
authors.forename: Kristof
authors.initials: K
authors.lastname: Grohe
authors.affiliation: Abteilung für NMR-basierte Strukturbiologie, Max Planck Institut für Biophysikalische Chemie, Am Faßberg 11, 37077, Göttingen, Germany.
authors.forename: Eszter Eva
authors.initials: EE
authors.lastname: Najbauer
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Frederik R
authors.initials: FR
authors.lastname: Ehrmann
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Nedyalka
authors.initials: N
authors.lastname: Radeva
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Zitzer
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Linne
authors.affiliation: Abteilung für NMR-basierte Strukturbiologie, Max Planck Institut für Biophysikalische Chemie, Am Faßberg 11, 37077, Göttingen, Germany.|Fakultät für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Haus F, 81377, München, Germany.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Linser
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Heine
authors.affiliation: Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032, Marburg, Germany.
authors.forename: Gerhard
authors.identifier: 0000-0002-4913-390X
authors.initials: G
authors.lastname: Klebe
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015195:Drug Design; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology; D008024:Ligands; D062105:Molecular Docking Simulation; D011485:Protein Binding; D054852:Small Molecule Libraries / Q000737:chemistry* / Q000494:pharmacology*; D020037:Sordariales / Q000201:enzymology*
chemical_list: D006571:Heterocyclic Compounds; D008024:Ligands; D054852:Small Molecule Libraries; D016282:Aspartic Acid Endopeptidases; C042466:Endothia aspartic proteinase
keywords: PAINS; drug discovery; fragment-based lead discovery; medicinal chemistry; reactivity