Monday, January 15, 2018

Novel K-Ras G12C Switch-II covalent binders destabilize Ras and accelerate nucleotide exchange

Chimno Ihuoma Nnadi, Meredith L. Jenkins, Daniel R. Gentile, Leslie A. Bateman, Daniel Zaidman, Trent E. Balius, Daniel K. Nomura, John E. Burke, Kevan M. Shokat, and Nir London

J. Chem. Inf. Model., Just Accepted Manuscript
DOI: 10.1021/acs.jcim.7b00399

The success of targeted covalent inhibitors in the global pharmaceutical industry has led to a resurgence of covalent drug discovery. However, covalent inhibitor design for flexible binding sites remains a difficult task due to lack of methodological development. Here, we compared covalent docking to empirical electrophile screening, against the highly dynamic target K-RasG12C. While the overall hit-rate of both methods was comparable, we were able to rapidly progress a docking hit to a potent irreversible covalent inhibitor that modifies the inactive, GDP-bound state of K-RasG12C. Hydrogen-deuterium exchange mass spectrometry was used to probe the protein dynamics of compound binding to the switch-II pocket and subsequent destabilization of the nucleotide-binding region. SOS-mediated nucleotide exchange assays showed that, contrary to prior switch-II pocket inhibitors, these compounds appear to accelerate nucleotide exchange. This study highlights the efficiency of covalent docking as a tool for the discovery of chemically novel hits against challenging targets.

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