Chemical Instability and Promiscuity of Arylmethylidenepyrazolinone-Based MDMX Inhibitors.

Stefaniak, Jakub, Lewis, Andrew M ORCID: https://orcid.org/0000-0002-6447-354X, Conole, Daniel, Galan, Sébastien RG, Bataille, Carole JR, Wynne, Graham M, Castaldi, M Paola, Lundbäck, Thomas, Russell, Angela J and Huber, Kilian VM (2018) Chemical Instability and Promiscuity of Arylmethylidenepyrazolinone-Based MDMX Inhibitors. ACS Chemical Biology, 13 (10). pp. 2849-2854. ISSN 1554-8929

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Abstract

Targeting the protein-protein interaction between p53 and MDM2/MDMX (MDM4) represents an attractive anticancer strategy for the treatment of p53-competent tumors. Several selective and potent MDM2 inhibitors have been developed and entered the clinic; however, the repertoire of MDMX antagonists is still limited. The arylmethylidenepyrazolinone SJ-172550 has been reported as a selective MDMX antagonist; yet, uncertainties about its mechanism of action have raised doubts about its use as a chemical probe. Here, we show that, in addition to its unclear mode of action, SJ-172550 is unstable in aqueous buffers, giving rise to side products of unknown biological activity. Using an SJ-172550-derived affinity probe, we observed promiscuous binding to cellular proteins whereas cellular thermal shift assays did not reveal a stabilizing effect on MDMX. Overall, our results raise further questions about the interpretation of data using SJ-172550 and related compounds to investigate cellular phenotypes.