Issue 45, 2018

Quantitation of ERK1/2 inhibitor cellular target occupancies with a reversible slow off-rate probe

Abstract

Target engagement is a key concept in drug discovery and its direct measurement can provide a quantitative understanding of drug efficacy and/or toxicity. Failure to demonstrate target occupancy in relevant cells and tissues has been recognised as a contributing factor to the low success rate of clinical drug development. Several techniques are emerging to quantify target engagement in cells; however, in situ measurements remain challenging, mainly due to technical limitations. Here, we report the development of a non-covalent clickable probe, based on SCH772984, a slow off-rate ERK1/2 inhibitor, which enabled efficient pull down of ERK1/2 protein via click reaction with tetrazine tagged agarose beads. This was used in a competition setting to measure relative target occupancy by selected ERK1/2 inhibitors. As a reference we used the cellular thermal shift assay, a label-free biophysical assay relying solely on ligand-induced thermodynamic stabilization of proteins. To validate the EC50 values measured by both methods, the results were compared with IC50 data for the phosphorylation of RSK, a downstream substrate of ERK1/2 used as a functional biomarker of ERK1/2 inhibition. We showed that a slow off-rate reversible probe can be used to efficiently pull down cellular proteins, significantly extending the potential of the approach beyond the need for covalent or photoaffinity warheads.

Graphical abstract: Quantitation of ERK1/2 inhibitor cellular target occupancies with a reversible slow off-rate probe

Supplementary files

Article information

Article type
Edge Article
Submitted
22 Jun 2018
Accepted
15 Sep 2018
First published
17 Sep 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2018,9, 8608-8618

Quantitation of ERK1/2 inhibitor cellular target occupancies with a reversible slow off-rate probe

H. Lebraud, O. Surova, A. Courtin, M. O'Reilly, C. R. Valenzano, P. Nordlund and T. D. Heightman, Chem. Sci., 2018, 9, 8608 DOI: 10.1039/C8SC02754D

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