ARS-853

Kinase experiment:

Purified KRAS (1 μM) is incubated EDTA (10 mM) and GDP (1 mM) or GTPγS (1 mM) at room temperature for 1 h followed by addition of MgCl2 (1 mM) to terminate the reaction. ARS853 (1 μM) is then added and the mixture is incubated for another hour at room temperature. HEK293 cells expressing various KRAS mutants are treated with ARS853. Proteins are extracted using a buffer containing 9M urea, 10 mM DTT and 50 mM ammonium bicarbonate, pH 8, heated to 65°C for 15 min and alkylated using 50 mM iodoacetamide at 37°C for 30 min. The samples are desalted by gel filtration in Zeba spin desalting plates followed by addition of sequencing-grade trypsin to a concentration of 10 μg/ml, and incubation for one hour at 37°C. Heavy isotopic standards (25 fmol) of the KRASG12C target peptide and KRAS normalization peptide are added to the samples followed by desalting in Strata-X polymeric reverse phase plates. LC-MS/MS analysis is performed in a Q Exactive quadrupole orbitrap mass spectrometer under standard condition. The amount of KRASG12C bound by the drug is determined by the ratio of the modified G12C peptide to that of the heavy isotopic standards[1].

References:

[1]. Lito P, et al. Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism. Science. 2016 Feb 5;351(6273):604-8.
[2]. Patricelli MP, et al. Selective Inhibition of Oncogenic KRAS Output with Small Molecules Targeting the Inactive State. Cancer Discov. 2016 Mar;6(3):316-29.