Transcriptional Inhibitors Identified in a 160,000-Compound Small-Molecule DUX4 Viability Screen

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The study is an extension of a previous smaller scale screen on 44,000 compounds. This larger screen generated a preliminary hit set of 640 compounds. We purchased 46 and found them to be generally similar in activity to those discovered from the previous screen. None of these 46, or of the 54 studied in detail from the previous screen, specifically inhibited DUX4 target gene expression, meaning that they protected cells from death but not by directly blocking DUX4, most likely by blocking a pathway downstream of DUX4. This was a disappointment given the scale of the project, so we decided to go back to the hit set of 640 compounds and test all of them for the ability to inhibit DUX4 target gene expression (640 real-time PCRs for Myo1g - not fun). But this did turn up several transcription inhibitors, 3 of which were specific to DUX4, i.e. they did not prevent the tet-on system from inducing DUX4 expression, but they did prevent DUX4 from inducing transcription of its targets. Although from a medicinal chemistry perspective these 3 compounds might not be ideal leads, they do demonstrate that it is feasible to identify specific transcriptional inhibitors of DUX4. Finally, as a byproduct of this screen, we also identified a number of inhibitors of the tet-on system.

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