Small Molecule Imaging Agent for Mutant KRAS G12C

Multiple potent covalent inhibitors for mutant KRAS G12C have been described and some are in clinical trials. These small molecule inhibitors potentially allow for companion imaging probe development, thereby expanding the chemical biology toolkit to investigate mutant KRAS biology. Herein, a series of fluorescent companion imaging drugs for KRAS G12C, using two scaffolds, ARS‐1323 and AMG‐510 is synthesized and tested. Four fluorescent derivatives of each by attaching BODIPY dyes are created. It is found that two fluorescent derivatives (BODIPY FL and BODIPY TMR) of ARS‐1323 bind mutant KRAS and can be used for biochemical binding screens. Unfortunately, these drugs cannot be used as direct imaging agents in cells, likely because of nonspecific membrane labeling. To circumvent this challenge, a two step procedure is then used in cancer cells where an ARS‐1323 alkyne is used for target binding followed by fluorescence imaging after in situ click chemistry with picolyl azide Alexa Fluor 647. It is shown that this approach can be used to image mutant KRAS G12C directly in cells. Given the current lack of mutant KRAS G12C specific antibodies, these reagents can be useful for specific fluorescence imaging. Multiple fluorescent derivatives of the KRAS G12C inhibitors are synthesized in an attempt to develop companion imaging agents. Multiple derivatives of ARS‐1323 bind recombinant KRAS G12C. Imaging of KRAS G12C in cells can be achieved using an ARS‐1323‐alkyne, followed by an in situ click chemistry reaction.