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Re-Evaluating the Mechanism of Action of α,β-Unsaturated Carbonyl DUB Inhibitors B-AP15 and VLX1570: A Paradigmatic Example of Unspecific Protein Crosslinking with Michael Acceptor Motif-Containing Drugs

submitted on 23.10.2019 and posted on 25.10.2019 by Jennifer Ward, Adán Pinto-Fernández, LoÏc Cornelissen, Sarah Bonham, Laura Diaz Saez, Olivier Riant, Kilian Huber, Benedikt M. Kessler, Olivier Feron, Edward W. Tate
Deubiquitinating enzymes are a growing target class across multiple disease states, with several inhibitors now reported. b-AP15 and VLX1570 are two structurally related USP14/UCH-37 inhibitors with a shared α,β-unsaturated carbonyl substructure motif. Initially taken forward into a phase I/II clinical trial for refractory multiple myeloma, VLX1570 has since been put on full clinical hold due to dose limiting toxicity. Through a proteomic approach, here we demonstrate that these compounds target a diverse range of proteins, resulting in the formation of higher molecular weight complexes. Activity-based proteome profiling identified CIAPIN1 as a sub-micromolar covalent target of VLX1570, and further analysis demonstrated that high molecular weight complex formation leads to aggregation of CIAPIN1 in intact cells. Our results suggest that in addition to DUB inhibition, these compounds induce non-specific protein aggregation through cross-linking, providing a molecular explanation for general cellular toxicity.


Email Address of Submitting Author


University of Oxford


United Kingdom

ORCID For Submitting Author


Declaration of Conflict of Interest

The authors declare no conflict of interest