Challenges for the Discovery of Non-Covalent WRN Helicase Inhibitors

The Werner Syndrome RecQ helicase (WRN) is a synthetic lethal target of interest for the treatment of cancers with microsatellite instability (MSI). Different hit finding approaches were initially tested. The identification of WRN inhibitors proved challenging due to a high propensity for artefacts via protein interference, i. e., hits inhibiting WRN enzymatic activities through multiple, unspecific mechanisms. Previously published WRN Helicase inhibitors (ML216, NSC19630 or NSC617145) were characterized in an extensive set of biochemical and biophysical assays and could be ruled out as specific WRN helicase probes. More innovative screening strategies need to be developed for successful drug discovery of non-covalent WRN helicase inhibitors. One of the major hurdles in targeting WRN helicase is to overcome the challenge of false positives in screening due to the high propensity of WRN to protein interferences. Biochemical and biophysical fingerprints of hits allow to triage the hits and highlight the artefacts, including compounds (ML216 and NSC617145) wrongly considered as specific WRN probes. image