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Identification and Structure–Activity Relationship of HDAC6 Zinc-Finger Ubiquitin Binding Domain Inhibitors

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posted on 09.05.2018, 20:03 by Renato Ferreira de Freitas, Rachel J. Harding, Ivan Franzoni, Mani Ravichandran, Mandeep K. Mann, Hui Ouyang, Mark Lautens, Vijayaratnam Santhakumar, Cheryl H. Arrowsmith, Matthieu Schapira
HDAC6 plays a central role in the recruitment of protein aggregates for lysosomal degradation and is a promising target for combination therapy with proteasome inhibitors in multiple myeloma. Pharmacologically displacing ubiquitin from the zinc-finger ubiquitin-binding domain (ZnF-UBD) of HDAC6 is an underexplored alternative to catalytic inhibition. Here, we present the discovery of an HDAC6 ZnF-UBD-focused chemical series and its progression from virtual screening hits to low micromolar inhibitors. A carboxylate mimicking the C-terminal extremity of ubiquitin, and an extended aromatic system stacking with W1182 and R1155, are necessary for activity. One of the compounds induced a conformational remodeling of the binding site where the primary binding pocket opens up onto a ligand-able secondary pocket that may be exploited to increase potency. The preliminary structure–activity relationship accompanied by nine crystal structures should enable further optimization into a chemical probe to investigate the merit of targeting the ZnF-UBD of HDAC6 in multiple myeloma and other diseases.